diff --git a/docs/01.CONFIGURATION.md b/docs/01.CONFIGURATION.md
index 1a263e73fa..506d280bfb 100644
--- a/docs/01.CONFIGURATION.md
+++ b/docs/01.CONFIGURATION.md
@@ -155,7 +155,7 @@ Enabling this feature provides detailed error messages where available, like lin
 
 ### Logging
 
-This option can be used to enable log messages during runtime. When enabled the engine will use the `jerry_port_log` port API function to print relevant log messages.
+This option can be used to enable log messages during runtime. When enabled the engine will use the `jerry_port_log_buffer` port API function to print relevant log messages.
 This feature is disabled by default.
 
 | Options |                                              |
diff --git a/docs/02.API-REFERENCE.md b/docs/02.API-REFERENCE.md
index 3610957414..8328b34124 100644
--- a/docs/02.API-REFERENCE.md
+++ b/docs/02.API-REFERENCE.md
@@ -751,7 +751,6 @@ typedef void (*jerry_value_free_callback_t) (void *native_p);
 
 **See also**
 
-- [jerry_string_external_sz](#jerry_string_external_sz)
 - [jerry_string_external](#jerry_string_external)
 - [jerry_arraybuffer_external](#jerry_arraybuffer_external)
 
@@ -809,7 +808,6 @@ typedef void (*jerry_external_string_free_cb_t) (jerry_char_t *string_p,
 **See also**
 
 - [jerry_string_external_on_free](#jerry_string_external_on_free)
-- [jerry_string_external_sz](#jerry_string_external_sz)
 - [jerry_string_external](#jerry_string_external)
 
 ## jerry_error_object_created_cb_t
@@ -1887,7 +1885,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_STRICT_MODE | JERRY_PARSE_HAS_SOURCE_NAME | JERRY_PARSE_HAS_START;
-  parse_options.source_name = jerry_string_sz ("hello.js");
+  parse_options.source_name = jerry_sz_ascii ("hello.js");
   /* This example script is extracted from the middle of a file. */
   parse_options.start_line = 10;
   parse_options.start_column = 1;
@@ -1920,7 +1918,7 @@ main (void)
   /* Specify the argument list to parse a function. */
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("a, b");
+  parse_options.argument_list = jerry_sz_ascii ("a, b");
 
   const jerry_char_t function_code[] = "return a + b;";
   jerry_value_t parsed_function = jerry_parse (function_code, sizeof (function_code) - 1, &parse_options);
@@ -1990,11 +1988,11 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t script_value = jerry_string_sz ("print ('Hello, World!');");
+  jerry_value_t script_value = jerry_sz_ascii ("print ('Hello, World!');");
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_STRICT_MODE | JERRY_PARSE_HAS_SOURCE_NAME | JERRY_PARSE_HAS_START;
-  parse_options.source_name = jerry_string_sz ("hello.js");
+  parse_options.source_name = jerry_sz_ascii ("hello.js");
   /* This example script is extracted from the middle of a file. */
   parse_options.start_line = 10;
   parse_options.start_column = 1;
@@ -3020,7 +3018,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string_value = jerry_string_sz ("Symbol description string");
+  jerry_value_t string_value = jerry_sz_ascii ("Symbol description string");
   jerry_value_t symbol_value = jerry_symbol_with_description (string_value);
 
   jerry_value_free (string_value);
@@ -3081,7 +3079,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string_value = jerry_string_sz ("12345678");
+  jerry_value_t string_value = jerry_sz_ascii ("12345678");
   jerry_value_t bigint_value = jerry_value_to_bigint (string_value);
 
   jerry_value_free (string_value);
@@ -3565,7 +3563,7 @@ main (void)
   jerry_value_t constructor = jerry_function_external (my_constructor);
 
   /* External functions does not have a prototype by default, so we need to create one */
-  jerry_value_t prototype_str = jerry_string_sz ("prototype");
+  jerry_value_t prototype_str = jerry_sz_ascii ("prototype");
   jerry_value_free (jerry_object_set (constructor, prototype_str, base_obj));
   jerry_value_free (prototype_str);
 
@@ -3750,7 +3748,7 @@ jerry_error_type (const jerry_value_t value);
 
 ```c
 {
-  jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_RANGE, "error msg");
+  jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_RANGE, jerry_sz_ascii ("error msg"));
   jerry_error_t error_type = jerry_error_type (error_obj);
 
   // error_type is now JERRY_ERROR_RANGE.
@@ -3868,7 +3866,7 @@ void main(void)
 
   jerry_error_on_created (error_object_created_callback, NULL);
 
-  jerry_value_free (jerry_error_sz (JERRY_ERROR_COMMON, "Message"));
+  jerry_value_free (jerry_error_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Message")));
 
   jerry_cleanup ();
 } /* main */
@@ -4062,7 +4060,7 @@ throw_exception (const jerry_call_info_t *call_info_p, /**< call info */
   (void) argv;
   (void) argc;
 
-  jerry_value_t result_value = jerry_throw_sz (JERRY_ERROR_COMMON, "Error!");
+  jerry_value_t result_value = jerry_throw_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Error!"));
 
   /* Ignore calling the vm_throw_callback function. */
   jerry_exception_allow_capture (result_value, false);
@@ -4079,7 +4077,7 @@ main (void)
 
   jerry_value_t global_object_value = jerry_current_realm ();
   jerry_value_t function_value = jerry_function_external (throw_exception);
-  jerry_value_t function_name_value = jerry_string_sz ("throw_exception");
+  jerry_value_t function_name_value = jerry_sz_ascii ("throw_exception");
 
   jerry_value_free (jerry_object_set (global_object_value, function_name_value, function_value));
   jerry_value_free (function_name_value);
@@ -4172,7 +4170,7 @@ jerry_string_size (const jerry_value_t value, JERRY_ENCODING_CESU8);
 ```c
 {
   const char char_array[] = "a string";
-  jerry_value_t string = jerry_string_sz (char_array);
+  jerry_value_t string = jerry_sz_ascii (char_array);
 
   jerry_size_t string_size = jerry_string_size (string, JERRY_ENCODING_CESU8);
 
@@ -4184,7 +4182,7 @@ jerry_string_size (const jerry_value_t value, JERRY_ENCODING_CESU8);
 
 **See also**
 
-- [jerry_string_sz](#jerry_string_sz)
+- [jerry_sz_ascii](#jerry_sz_ascii)
 - [jerry_string_length](#jerry_string_length)
 - [jerry_validate_string](#jerry_validate_string)
 
@@ -4215,7 +4213,7 @@ jerry_string_length (const jerry_value_t value);
 ```c
 {
   const char char_array[] = "a string";
-  jerry_value_t string = jerry_string_sz (char_array);
+  jerry_value_t string = jerry_sz_ascii (char_array);
 
   jerry_length_t string_length = jerry_string_length (string);
 
@@ -4227,7 +4225,7 @@ jerry_string_length (const jerry_value_t value);
 
 **See also**
 
-- [jerry_string_sz](#jerry_string_sz)
+- [jerry_sz_ascii](#jerry_sz_ascii)
 - [jerry_string_size](#jerry_string_size)
 - [jerry_validate_string](#jerry_validate_string)
 
@@ -4279,7 +4277,7 @@ main (void)
 
   jerry_value_t value;
   // create or copy value
-  value = jerry_string_sz ("Demo string");
+  value = jerry_sz_ascii ("Demo string");
 
   // Read the string into a byte buffer.
   jerry_size_t string_size = jerry_string_size (value, JERRY_ENCODING_CESU8);
@@ -4301,7 +4299,7 @@ main (void)
 
 **See also**
 
-- [jerry_string_sz](#jerry_string_sz)
+- [jerry_sz_ascii](#jerry_sz_ascii)
 - [jerry_string_size](#jerry_string_size)
 - [jerry_strig_to_buffer](#jerry_strig_to_buffer)
 
@@ -4353,8 +4351,8 @@ main (void)
 
   jerry_string_external_on_free (external_string_free_callback);
 
-  const char *string_p = "This is a long external string, should not be duplicated!";
-  jerry_value_t external_string = jerry_string_external_sz (string_p, NULL);
+#define string_p "This is a long external string, should not be duplicated!"
+  jerry_value_t external_string = jerry_string_external (JERRY_ZSTR_ARG (string_p), NULL);
   /* The external_string_free_callback is called. */
   jerry_value_free (external_string);
 
@@ -4367,7 +4365,6 @@ main (void)
 
 - [jerry_external_string_free_cb_t](#jerry_external_string_free_cb_t)
 - [jerry_string_user_ptr](#jerry_string_user_ptr)
-- [jerry_string_external_sz](#jerry_string_external_sz)
 - [jerry_string_external](#jerry_string_external)
 
 
@@ -4381,7 +4378,7 @@ Returns the user pointer assigned to an external string.
   - In some cases (e.g. when the string is also a magic string registered by
     [jerry_register_magic_strings](#jerry_register_magic_strings)), the
     string is a normal string without a user pointer even if it is created
-    by [jerry_string_external_sz](#jerry_string_external_sz).
+    by [jerry_string_external](#jerry_string_external).
 
 **Prototype**
 
@@ -4414,9 +4411,9 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  const char *string_p = "This is a long external string, should not be duplicated!";
+#define string_p "This is a long external string, should not be duplicated!"
 
-  jerry_value_t external_string = jerry_string_external_sz (string_p, (void *) &user_value);
+  jerry_value_t external_string = jerry_string_external (JERRY_ZSTR_ARG (string_p), (void *) &user_value);
 
   bool is_external;
   void *user_p = jerry_string_user_ptr (external_string, &is_external);
@@ -4437,7 +4434,6 @@ main (void)
 **See also**
 
 - [jerry_string_set_external_string_free_callback](#jerry_string_set_external_string_free_callback)
-- [jerry_string_external_sz](#jerry_string_external_sz)
 - [jerry_string_external](#jerry_string_external)
 
 
@@ -4867,7 +4863,7 @@ module_resolve_callback (const jerry_value_t specifier,
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("b.mjs");
+  parse_options.source_name = jerry_sz_ascii ("b.mjs");
 
   jerry_value_t result = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -4883,7 +4879,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t ret_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -4941,7 +4937,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5002,7 +4998,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5081,7 +5077,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5140,8 +5136,8 @@ module_import_meta_callback (const jerry_value_t module, /**< module */
   (void) user_p;
 
   /* Create a property for the meta object */
-  jerry_value_t property_name_value = jerry_string_sz ("prop");
-  jerry_value_t property_value = jerry_string_sz ("prop");
+  jerry_value_t property_name_value = jerry_sz_ascii ("prop");
+  jerry_value_t property_value = jerry_sz_ascii ("prop");
   jerry_value_t result_value = jerry_object_set (meta_object, property_name_value, property_value);
   jerry_value_free (result_value);
   jerry_value_free (property_value);
@@ -5220,7 +5216,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5292,7 +5288,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5359,7 +5355,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("a.mjs");
+  parse_options.source_name = jerry_sz_ascii ("a.mjs");
 
   jerry_value_t module_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5461,11 +5457,11 @@ main (void)
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME | JERRY_PARSE_HAS_USER_VALUE;
 
   /* Resource is usually used for debugging purposes, e.g. for generating backtrace. */
-  parse_options.source_name = jerry_string_sz ("dir/my_script.js");
+  parse_options.source_name = jerry_sz_ascii ("dir/my_script.js");
 
   /* User value should provide information for resolving dynamic imports.
    * In this case it contains the full path excluding the filename. */
-  parse_options.user_value = jerry_string_sz ("/home/user/dir");
+  parse_options.user_value = jerry_sz_ascii ("/home/user/dir");
 
   jerry_value_t script_value = jerry_parse (script, sizeof (script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5478,8 +5474,8 @@ main (void)
   const jerry_char_t module_script[] = "export var a = 5";
 
   parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME | JERRY_PARSE_HAS_USER_VALUE;
-  parse_options.source_name = jerry_string_sz ("modules/my_module.mjs");
-  parse_options.user_value = jerry_string_sz ("/home/user/dir/modules");
+  parse_options.source_name = jerry_sz_ascii ("modules/my_module.mjs");
+  parse_options.user_value = jerry_sz_ascii ("/home/user/dir/modules");
 
   jerry_value_t module_value = jerry_parse (module_script, sizeof (module_script) - 1, &parse_options);
   jerry_value_free (parse_options.source_name);
@@ -5556,8 +5552,8 @@ main (void)
 
   jerry_value_t exports[2] =
   {
-    jerry_string_sz ("first_export"),
-    jerry_string_sz ("second_export")
+    jerry_sz_ascii ("first_export"),
+    jerry_sz_ascii ("second_export")
   };
 
   jerry_value_t native_module = jerry_native_module (NULL, exports, 2);
@@ -5617,7 +5613,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t export = jerry_string_sz ("an_export");
+  jerry_value_t export = jerry_sz_ascii ("an_export");
 
   jerry_value_t native_module = jerry_native_module (NULL, &export, 1);
 
@@ -5678,7 +5674,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t export = jerry_string_sz ("an_export");
+  jerry_value_t export = jerry_sz_ascii ("an_export");
 
   jerry_value_t native_module = jerry_native_module (NULL, &export, 1);
 
@@ -5941,7 +5937,7 @@ jerry_property_descriptor_to_object (const jerry_property_descriptor_t *src_prop
 static void
 example (void)
 {
-  jerry_value_t prop_name = jerry_string_sz ("value");
+  jerry_value_t prop_name = jerry_sz_ascii ("value");
 
   jerry_property_descriptor_t prop_desc = jerry_property_descriptor ();
 
@@ -5994,7 +5990,7 @@ static void
 example (void)
 {
   jerry_value_t object = jerry_object ();
-  jerry_value_t prop_name = jerry_string_sz ("value");
+  jerry_value_t prop_name = jerry_sz_ascii ("value");
   jerry_value_t value = jerry_boolean (true);
   jerry_property_descriptor_t prop_desc;
 
@@ -6218,7 +6214,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string_value = jerry_string_sz ("foo");
+  jerry_value_t string_value = jerry_sz_ascii ("foo");
   jerry_value_t symbol_value = jerry_symbol_with_description (string_value);
 
   jerry_value_free (string_value);
@@ -6276,7 +6272,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string_value = jerry_string_sz ("foo");
+  jerry_value_t string_value = jerry_sz_ascii ("foo");
   jerry_value_t symbol_value = jerry_symbol_with_description (string_value);
 
   jerry_value_free (string_value);
@@ -6926,7 +6922,7 @@ jerry_error (jerry_error_t error_type, jerry_value_t message);
 
 ```c
 {
-  jerry_value_t message = jerry_string_sz ("error");
+  jerry_value_t message = jerry_sz_ascii ("error");
   jerry_value_t error_obj = jerry_error (JERRY_ERROR_COMMON, message);
 
   ... // usage of error_obj
@@ -6948,7 +6944,9 @@ jerry_error (jerry_error_t error_type, jerry_value_t message);
 
 **Summary**
 
-Create new JavaScript Error object, using the a zero-terminated string as the error message.
+Create an Error object with the provided string value as the error `message`.
+If the `message` value is not a string, the created error will not have a message property.
+The `message` will be freed in this function.
 
 *Note*: Returned value must be freed with [jerry_value_free](#jerry_value_free) when it
 is no longer needed.
@@ -6957,18 +6955,18 @@ is no longer needed.
 
 ```c
 jerry_value_t
-jerry_error_sz (jerry_error_t error_type, const char *message_p);
+jerry_error_sz (jerry_error_t error_type, const jerry_value_t message);
 ```
 
 - `error_type` - type of the error
-- `message_p` - value of 'message' property of the constructed error object
+- `message` - message of the error that will be free/take
 - return value - constructed error object
 
 **Example**
 
 ```c
 {
-  jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_TYPE, "error");
+  jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"));
 
   ... // usage of error_obj
 
@@ -7090,7 +7088,7 @@ main (void)
   jerry_value_t glob_obj = jerry_current_realm ();
 
   // after this, script can invoke the native handler through "handler_field (1, 2, 3);"
-  jerry_value_t prop_name = jerry_string_sz ("handler_field");
+  jerry_value_t prop_name = jerry_sz_ascii ("handler_field");
   // set property and release the return value without any check
   jerry_value_free (jerry_object_set (glob_obj, prop_name, func_val));
   jerry_value_free (prop_name);
@@ -7468,11 +7466,11 @@ main (void)
 - [jerry_value_free](#jerry_value_free)
 
 
-## jerry_string_sz
+## jerry_sz_ascii
 
 **Summary**
 
-Create string from a zero-terminated ASCII string.
+Create string from a zero-terminated ASCII string literal.
 
 *Note*: Returned value must be freed with [jerry_value_free](#jerry_value_free) when it
 is no longer needed.
@@ -7481,7 +7479,7 @@ is no longer needed.
 
 ```c
 jerry_value_t
-jerry_string_sz (const char *str_p);
+jerry_sz_ascii (const char *str_p);
 ```
 
 - `str_p` - non-null pointer to string
@@ -7492,7 +7490,7 @@ jerry_string_sz (const char *str_p);
 ```c
 {
   const char char_array[] = "a string";
-  jerry_value_t string_value = jerry_string_sz (char_array);
+  jerry_value_t string_value = jerry_sz_ascii (char_array);
 
   ... // usage of string_value
 
@@ -7547,55 +7545,7 @@ jerry_string (const jerry_char_t *buffer_p,
 **See also**
 
 - [jerry_validate_string](#jerry_validate_string)
-- [jerry_string_sz](#jerry_string_sz)
-
-
-## jerry_string_external_sz
-
-**Summary**
-
-Create an external string from a zero-terminated ASCII string. The string buffer passed to the function
-should not be modified until the free callback is called. This function can be used to avoid
-the duplication of large strings.
-
-*Note*:
- - The free callback can be set by [jerry_string_external_on_free](#jerry_string_external_on_free)
- - Returned value must be freed with [jerry_value_free](#jerry_value_free)
-   when it is no longer needed.
-
-**Prototype**
-
-```c
-jerry_value_t
-jerry_string_external_sz (const char *str_p, void *user_p);
-```
-
-- `str_p` - non-null pointer to string
-- `user_p` - user pointer passed to the callback when the string is freed
-- return value - value of the created string
-
-*New in version 2.4*.
-
-*Changed in version [[NEXT_RELEASE]]*: `free_cb` is replaced by `user_p`.
-
-**Example**
-
-```c
-{
-  const char* string_p = "a large and immutable string: this is a story about ....";
-  jerry_value_t string_value = jerry_string_external_sz (string_p, NULL);
-
-  ... // usage of string_value
-
-  jerry_value_free (string_value);
-}
-```
-
-**See also**
-
-- [jerry_string_external](#jerry_string_external)
-- [jerry_string_external_on_free](#jerry_string_external_on_free)
-
+- [jerry_sz_ascii](#jerry_sz_ascii)
 
 ## jerry_string_external
 
@@ -7647,7 +7597,7 @@ jerry_string_external (const jerry_char_t *str_p,
 **See also**
 
 - [jerry_validate_string](#jerry_validate_string)
-- [jerry_string_external_sz](#jerry_string_external_sz)
+- [jerry_string_external](#jerry_string_external)
 - [jerry_string_external_on_free](#jerry_string_external_on_free)
 
 
@@ -7688,7 +7638,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string_value = jerry_string_sz ("Symbol description string");
+  jerry_value_t string_value = jerry_sz_ascii ("Symbol description string");
   jerry_value_t symbol_value = jerry_symbol_with_description (string_value);
 
   // The description value is no longer needed
@@ -7794,10 +7744,10 @@ jerry_regexp_sz (const jerry_char_t *pattern_p, uint16_t flags);
 
 ```c
 {
-  jerry_char_t pattern_p = "[cgt]gggtaaa|tttaccc[acg]";
+#define pattern "[cgt]gggtaaa|tttaccc[acg]"
   uint16_t pattern_flags = JERRY_REGEXP_FLAG_IGNORE_CASE;
 
-  jerry_value_t regexp = jerry_regexp_sz (pattern_p, pattern_flags);
+  jerry_value_t regexp = jerry_regexp_sz (jerry_sz_ascii (pattern), pattern_flags);
 
   ...
 
@@ -8220,7 +8170,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("handler_field");
+  jerry_value_t prop_name = jerry_sz_ascii ("handler_field");
 
   jerry_value_t has_prop_js = jerry_object_has (global_object, prop_name);
   bool has_prop = jerry_value_is_true (has_prop_js);
@@ -8281,7 +8231,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("handler_field");
+  jerry_value_t prop_name = jerry_sz_ascii ("handler_field");
 
   jerry_value_t has_prop_js = jerry_object_has_own (global_object, prop_name);
   bool has_prop = jerry_value_is_true (has_prop_js);
@@ -8343,7 +8293,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("hidden_property");
+  jerry_value_t prop_name = jerry_sz_ascii ("hidden_property");
 
   bool has_internal_js_prop = jerry_object_has_internal (global_object, prop_name);
 
@@ -8386,7 +8336,7 @@ jerry_object_delete (const jerry_value_t obj_val,
 ```c
 {
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("my_prop");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_prop");
 
   jerry_value_t delete_result = jerry_object_delete (global_object, prop_name);
   /* use "delete_result" */
@@ -8482,7 +8432,7 @@ jerry_object_delete_internal (const jerry_value_t obj_val,
 ```c
 {
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("hidden_property");
+  jerry_value_t prop_name = jerry_sz_ascii ("hidden_property");
 
   bool delete_result = jerry_object_delete_internal (global_object, prop_name);
   /* use "delete_result" */
@@ -8535,7 +8485,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("Object");
+  jerry_value_t prop_name = jerry_sz_ascii ("Object");
 
   jerry_value_t prop_value = jerry_object_get (global_object, prop_name);
 
@@ -8656,7 +8606,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("Object");
+  jerry_value_t prop_name = jerry_sz_ascii ("Object");
 
   bool found;
   jerry_value_t prop_value = jerry_object_find_own (global_object, prop_name, global_object, &found);
@@ -8723,7 +8673,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("hidden_property");
+  jerry_value_t prop_name = jerry_sz_ascii ("hidden_property");
 
   jerry_value_t prop_value = jerry_object_get_internal (global_object, prop_name);
 
@@ -8778,7 +8728,7 @@ jerry_object_set (const jerry_value_t obj_val,
   ... // create or copy value to set
 
   jerry_value_t glob_obj = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("my_prop");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_prop");
 
   jerry_value_t set_result = jerry_object_set (glob_obj, prop_name, value_to_set);
 
@@ -8902,7 +8852,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("hidden_property");
+  jerry_value_t prop_name = jerry_sz_ascii ("hidden_property");
   jerry_value_t value_to_set = jerry_number (5);
 
   bool set_result = jerry_object_set_internal (global_object, prop_name, value_to_set);
@@ -9026,7 +8976,7 @@ main (void)
   prop_desc.value = value_to_set;
 
   // add the property as "my_prop" for the global object
-  jerry_value_t prop_name = jerry_string_sz ("my_prop");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_prop");
   jerry_value_t return_value = jerry_object_define_own_prop (global_obj_val, prop_name, &prop_desc);
   if (jerry_value_is_exception (return_value))
   {
@@ -9110,7 +9060,7 @@ main (void)
   prop_desc.setter = jerry_function_external (method_setter);
 
   // add the property as "my_prop" for the global object
-  jerry_value_t prop_name = jerry_string_sz ("my_prop");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_prop");
   jerry_value_t return_value = jerry_object_define_own_prop (global_obj_val, prop_name, &prop_desc);
   if (jerry_value_is_exception (return_value))
   {
@@ -9178,7 +9128,7 @@ jerry_object_get_own_prop (const jerry_value_t obj_val,
 
   jerry_property_descriptor_t prop_desc = jerry_property_descriptor ();
 
-  jerry_value_t prop_name = jerry_string_sz ("my_prop");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_prop");
   jerry_object_get_own_prop (global_obj_val, prop_name, &prop_desc);
   jerry_value_free (prop_name);
 
@@ -10049,7 +9999,7 @@ main (void)
   /* Construct an example object with a single property. */
   jerry_value_t object = jerry_object ();
   {
-    jerry_value_t test_property = jerry_string_sz ("DemoProp");
+    jerry_value_t test_property = jerry_sz_ascii ("DemoProp");
     jerry_value_t test_value = jerry_number (3);
     /* By default all properties added to an object are enumerable. */
     jerry_value_t set_result = jerry_object_set (object, test_property, test_value);
@@ -10157,7 +10107,7 @@ main (void)
     jerry_value_t test_object = jerry_object ();
 
     {
-      jerry_value_t test_property = jerry_string_sz ("DemoProp");
+      jerry_value_t test_property = jerry_sz_ascii ("DemoProp");
       jerry_value_t test_value = jerry_number (3);
       jerry_value_t set_result = jerry_object_set (test_object, test_property, test_value);
       /* The `set_result` should be checked if it is an exception or not. */
@@ -10169,7 +10119,7 @@ main (void)
     {
       /* Register the test object into the global object. */
       jerry_value_t global_object = jerry_current_realm ();
-      jerry_value_t demo_property = jerry_string_sz ("DemoObject");
+      jerry_value_t demo_property = jerry_sz_ascii ("DemoObject");
       jerry_value_t set_result = jerry_object_set (global_object, demo_property, test_object);
       /* The `set_result` should be checked if it is an exception or not. */
       jerry_value_free (set_result);
@@ -10183,7 +10133,7 @@ main (void)
   /* Look up the test object base on a property name. */
   find_my_object_info_t search_info =
   {
-    .property_name = jerry_string_sz ("DemoProp")
+    .property_name = jerry_sz_ascii ("DemoProp")
   };
 
   if (jerry_foreach_live_object (find_my_object, &search_info))
@@ -10300,7 +10250,7 @@ add_object_with_nativeptr (int foo_value)
 
   /* Register the test object into the global object. */
   jerry_value_t global_object = jerry_current_realm ();
-  jerry_value_t demo_property = jerry_string_sz ("DemoObject");
+  jerry_value_t demo_property = jerry_sz_ascii ("DemoObject");
   jerry_value_t set_result = jerry_object_set (global_object, demo_property, test_object);
   /* The `set_result` should be checked if it is an exception or not. */
   jerry_value_free (set_result);
@@ -10679,7 +10629,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("a, b");
+  parse_options.argument_list = jerry_sz_ascii ("a, b");
 
   jerry_value_t parse_result = jerry_parse (function_to_snapshot,
                                             sizeof (function_to_snapshot) - 1,
@@ -10911,7 +10861,7 @@ main (void)
   /* Register the "capture_backtrace" method. */
   {
     jerry_value_t func = jerry_function_external (backtrace_handler);
-    jerry_value_t name = jerry_string_sz ("backtrace");
+    jerry_value_t name = jerry_sz_ascii ("backtrace");
     jerry_value_t result = jerry_object_set (global, name, func);
     jerry_value_free (result);
     jerry_value_free (name);
@@ -10927,7 +10877,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("demo_memory.js");
+  parse_options.source_name = jerry_sz_ascii ("demo_memory.js");
 
   jerry_value_t program = jerry_parse ((const jerry_char_t *) source,
                                        strlen (source),
@@ -11016,7 +10966,7 @@ main (void)
   /* Register the "dump_backtrace" method. */
   {
     jerry_value_t func = jerry_function_external (backtrace_handler);
-    jerry_value_t name = jerry_string_sz ("backtrace");
+    jerry_value_t name = jerry_sz_ascii ("backtrace");
     jerry_value_t result = jerry_object_set (global, name, func);
     jerry_value_free (result);
     jerry_value_free (name);
@@ -11032,7 +10982,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("demo_backtrace.js");
+  parse_options.source_name = jerry_sz_ascii ("demo_backtrace.js");
 
   jerry_value_t program = jerry_parse ((const jerry_char_t *) source,
                                        strlen (source),
@@ -11402,7 +11352,7 @@ vm_exec_stop_callback (void *user_p)
   }
 
   // The value will be automatically wrapped into an exception.
-  return jerry_string_sz ("Abort script");
+  return jerry_sz_ascii ("Abort script");
 }
 
 int
@@ -11487,7 +11437,7 @@ main (void)
   /* Register the sourceName" method. */
   {
     jerry_value_t func = jerry_function_external (source_name_handler);
-    jerry_value_t name = jerry_string_sz ("sourceName");
+    jerry_value_t name = jerry_sz_ascii ("sourceName");
     jerry_value_t result = jerry_object_set (global, name, func);
     jerry_value_free (result);
     jerry_value_free (name);
@@ -11500,7 +11450,7 @@ main (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("demo.js");
+  parse_options.source_name = jerry_sz_ascii ("demo.js");
 
   jerry_value_t program = jerry_parse (source,
                                        sizeof (source) - 1,
@@ -12738,8 +12688,8 @@ main (void)
 
   jerry_value_t obj = jerry_object ();
   {
-    jerry_value_t key = jerry_string_sz ("name");
-    jerry_value_t value = jerry_string_sz ("John");
+    jerry_value_t key = jerry_sz_ascii ("name");
+    jerry_value_t value = jerry_sz_ascii ("John");
     jerry_value_free (jerry_object_set (obj, key, value));
     jerry_value_free (key);
     jerry_value_free (value);
@@ -12876,7 +12826,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t map = jerry_container (JERRY_CONTAINER_TYPE_MAP, NULL, 0);
-  jerry_value_t key_str = jerry_string_sz ("number");
+  jerry_value_t key_str = jerry_sz_ascii ("number");
   jerry_value_t number = jerry_number (10);
   jerry_value_t args[2] = {key_str, number};
 
diff --git a/docs/03.API-EXAMPLE.md b/docs/03.API-EXAMPLE.md
index e8616cc44e..6c844e218f 100644
--- a/docs/03.API-EXAMPLE.md
+++ b/docs/03.API-EXAMPLE.md
@@ -168,7 +168,7 @@ This method will be implemented in C and will be called from the JavaScript code
 For this a few extra API methods are required:
 
 - `jerry_current_realm`
-- `jerry_string_sz`
+- `jerry_sz_ascii`
 - `jerry_object_set`
 - `jerry_function_external`
 
@@ -207,7 +207,7 @@ main (void)
     /* Get the "global" object */
     jerry_value_t global_object = jerry_current_realm ();
     /* Create a "print" JS string */
-    jerry_value_t property_name_print = jerry_string_sz ("print");
+    jerry_value_t property_name_print = jerry_sz_ascii ("print");
     /* Create a function from a native C method (this function will be called from JS) */
     jerry_value_t property_value_func = jerry_function_external (print_handler);
     /* Add the "print" property with the function value to the "global" object */
@@ -326,7 +326,7 @@ main (void)
     /* Get the "global" object */
     jerry_value_t global_object = jerry_current_realm ();
     /* Create a "print" JS string */
-    jerry_value_t property_name_print = jerry_string_sz ("print");
+    jerry_value_t property_name_print = jerry_sz_ascii ("print");
     /* Create a function from a native C method (this function will be called from JS) */
     jerry_value_t property_value_func = jerry_function_external (print_handler);
     /* Add the "print" property with the function value to the "global" object */
@@ -393,9 +393,17 @@ In this example the following extension methods are used:
 
 In further examples this "print" handler will be used.
 
+The `api-example-6.c` file should contain the following code:
+
+[doctest]: # ()
+
 ```c
+#include <stdio.h>
+
 #include "jerryscript.h"
+
 #include "jerryscript-ext/handlers.h"
+#include "jerryscript-ext/properties.h"
 
 int
 main (void)
@@ -407,7 +415,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register 'print' function from the extensions to the global object */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Setup Global scope code */
   jerry_value_t parsed_code = jerry_parse (script, script_size, NULL);
@@ -470,14 +478,14 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register 'print' function from the extensions */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Getting pointer to the Global object */
   jerry_value_t global_object = jerry_current_realm ();
 
   /* Constructing strings */
-  jerry_value_t prop_name = jerry_string_sz ("my_var");
-  jerry_value_t prop_value = jerry_string_sz ("Hello from C!");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_var");
+  jerry_value_t prop_value = jerry_sz_ascii ("Hello from C!");
 
   /* Setting the string value as a property of the Global object */
   jerry_value_t set_result = jerry_object_set (global_object, prop_name, prop_value);
@@ -729,7 +737,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register 'print' function from the extensions */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   while (!is_done)
   {
@@ -808,10 +816,8 @@ In this example (`api-example-9.c`) an object with a native function is added to
 #include "jerryscript-ext/handlers.h"
 #include "jerryscript-ext/properties.h"
 
-struct my_struct
-{
-  const char *msg;
-} my_struct;
+
+jerry_string_t my_struct;
 
 /**
  * Get a string from a native object
@@ -821,7 +827,7 @@ get_msg_handler (const jerry_call_info_t *call_info_p, /**< call information */
                  const jerry_value_t *args_p, /**< function arguments */
                  const jerry_length_t args_cnt) /**< number of function arguments */
 {
-  return jerry_string_sz (my_struct.msg);
+  return jerry_string_ascii (my_struct.ptr, my_struct.size);
 } /* get_msg_handler */
 
 int
@@ -831,10 +837,13 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register 'print' function from the extensions */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Do something with the native object */
-  my_struct.msg = "Hello, World!";
+  {
+    static const jerry_string_t hello = { JERRY_ZSTR_ARG ("Hello, World!") };
+    my_struct = hello;
+  }
 
   /* Create an empty JS object */
   jerry_value_t object = jerry_object ();
@@ -843,7 +852,7 @@ main (void)
   jerry_value_t func_obj = jerry_function_external (get_msg_handler);
 
   /* Set the native function as a property of the empty JS object */
-  jerry_value_t prop_name = jerry_string_sz ("myFunc");
+  jerry_value_t prop_name = jerry_sz_ascii ("myFunc");
   jerry_value_free (jerry_object_set (object, prop_name, func_obj));
   jerry_value_free (prop_name);
   jerry_value_free (func_obj);
@@ -852,7 +861,7 @@ main (void)
   jerry_value_t global_object = jerry_current_realm ();
 
   /* Add the JS object to the global context */
-  prop_name = jerry_string_sz ("MyObject");
+  prop_name = jerry_sz_ascii ("MyObject");
   jerry_value_free (jerry_object_set (global_object, prop_name, object));
   jerry_value_free (prop_name);
   jerry_value_free (object);
@@ -928,7 +937,7 @@ add_handler (const jerry_call_info_t *call_info_p, /**< call information */
   /* Note: that the argument count check is ignored for the example's case */
 
   /* Get 'this.x' */
-  jerry_value_t prop_name = jerry_string_sz ("x");
+  jerry_value_t prop_name = jerry_sz_ascii ("x");
   jerry_value_t x_val = jerry_object_get (call_info_p->this_value, prop_name);
 
   if (!jerry_value_is_exception (x_val))
@@ -958,7 +967,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register 'print' function from the extensions */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Create a JS object */
   const jerry_char_t my_js_object[] = " \
@@ -983,7 +992,7 @@ main (void)
   jerry_value_t add_func_obj = jerry_function_external (add_handler);
 
   /* Set the native function as a property of previously created MyObject */
-  jerry_value_t prop_name = jerry_string_sz ("add2x");
+  jerry_value_t prop_name = jerry_sz_ascii ("add2x");
   jerry_value_free (jerry_object_set (my_js_obj_val, prop_name, add_func_obj));
   jerry_value_free (add_func_obj);
   jerry_value_free (prop_name);
@@ -1058,7 +1067,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register the print function */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Evaluate the script */
   jerry_value_t eval_ret = jerry_eval (script, sizeof (script) - 1, JERRY_PARSE_NO_OPTS);
diff --git a/docs/05.PORT-API.md b/docs/05.PORT-API.md
index 298a1c4402..bdacf42f65 100644
--- a/docs/05.PORT-API.md
+++ b/docs/05.PORT-API.md
@@ -112,8 +112,11 @@ void jerry_port_context_free (void);
  *
  * The implementation can decide whether error and debug messages are logged to
  * the console, or saved to a database or to a file.
+ *
+ * @param buffer_p: input buffer
+ * @param buffer_size: data size
  */
-void jerry_port_log (const char *message_p);
+void jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
 ```
 
 ```c
diff --git a/docs/07.DEBUGGER.md b/docs/07.DEBUGGER.md
index 09c9c582d6..e2af036a3b 100644
--- a/docs/07.DEBUGGER.md
+++ b/docs/07.DEBUGGER.md
@@ -318,9 +318,8 @@ wait_for_source_callback (const jerry_char_t *source_name_p, /**< source name */
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string ((const jerry_char_t *) source_name_p,
-                                              (jerry_size_t) source_name_size,
-                                              JERRY_ENCODING_UTF8);
+  parse_options.source_name = jerry_string_utf8 ((const jerry_char_t *) source_name_p,
+                                                 (jerry_size_t) source_name_size);
 
   jerry_value_t ret_val = jerry_parse (source_p,
                                        source_size,
diff --git a/docs/09.EXT-REFERENCE-ARG.md b/docs/09.EXT-REFERENCE-ARG.md
index 191bb627f3..95efef412a 100644
--- a/docs/09.EXT-REFERENCE-ARG.md
+++ b/docs/09.EXT-REFERENCE-ARG.md
@@ -612,6 +612,7 @@ jerryx_arg_object_properties (const jerryx_arg_object_props_t *obj_prop_p,
 
 ```c
 #include "jerryscript.h"
+
 #include "jerryscript-ext/arg.h"
 
 /**
@@ -628,39 +629,31 @@ my_external_handler (const jerry_value_t function_obj,
 {
   bool required_bool;
   double required_num;
-  double optional_num = 1234.567;  // default value
+  double optional_num = 1234.567; // default value
 
   /* "prop_name_p" defines the name list of the expected properties' names. */
-  const char *prop_name_p[] = { "enable", "data", "extra_data" };
+  const jerry_value_t prop_name_p[] = { jerry_sz_ascii ("enable"),
+                                        jerry_sz_ascii ("data"),
+                                        jerry_sz_ascii ("extra_data") };
 
   /* "prop_mapping" defines the steps to transform properties to C variables. */
-  const jerryx_arg_t prop_mapping[] =
-  {
-    jerryx_arg_boolean (&required_bool, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
-    jerryx_arg_number (&required_num, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
-    jerryx_arg_number (&optional_num, JERRYX_ARG_COERCE, JERRYX_ARG_OPTIONAL)
-  };
+  const jerryx_arg_t prop_mapping[] = { jerryx_arg_boolean (&required_bool, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
+                                        jerryx_arg_number (&required_num, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
+                                        jerryx_arg_number (&optional_num, JERRYX_ARG_COERCE, JERRYX_ARG_OPTIONAL) };
 
   /* Prepare the jerryx_arg_object_props_t instance. */
-  const jerryx_arg_object_props_t prop_info =
-  {
-    .name_p = (const jerry_char_t **) prop_name_p,
-    .name_cnt = 3,
-    .c_arg_p = prop_mapping,
-    .c_arg_cnt = 3
-  };
+  const jerryx_arg_object_props_t prop_info = { .name_p = prop_name_p,
+                                                .name_cnt = 3,
+                                                .c_arg_p = prop_mapping,
+                                                .c_arg_cnt = 3 };
 
   /* It is the mapping used in the jerryx_arg_transform_args. */
-  const jerryx_arg_t mapping[] =
-  {
-    jerryx_arg_object_properties (&prop_info, JERRYX_ARG_REQUIRED)
-  };
+  const jerryx_arg_t mapping[] = { jerryx_arg_object_properties (&prop_info, JERRYX_ARG_REQUIRED) };
+
+  jerry_value_list_free (prop_name_p, sizeof (prop_name_p) / sizeof (prop_name_p[0]));
 
   /* Validate and transform. */
-  const jerry_value_t rv = jerryx_arg_transform_args (args_p,
-                                                      args_count,
-                                                      mapping,
-                                                      1);
+  const jerry_value_t rv = jerryx_arg_transform_args (args_p, args_count, mapping, 1);
 
   if (jerry_value_is_exception (rv))
   {
@@ -673,9 +666,8 @@ my_external_handler (const jerry_value_t function_obj,
    * required_bool, required_num and optional_num can now be used.
    */
 
-   return jerry_undefined (); /* Or return something more meaningful. */
+  return jerry_undefined (); /* Or return something more meaningful. */
 }
-
 ```
 
  **See also**
diff --git a/docs/10.EXT-REFERENCE-HANDLER.md b/docs/10.EXT-REFERENCE-HANDLER.md
index 5767ee27d0..1df81efe55 100644
--- a/docs/10.EXT-REFERENCE-HANDLER.md
+++ b/docs/10.EXT-REFERENCE-HANDLER.md
@@ -120,8 +120,8 @@ main (int argc, char **argv)
 
   jerryx_property_entry methods[] =
   {
-    { "demo", jerry_function_external (handler) },
-    { NULL, 0 },
+    JERRYX_PROPERTY_FUNCTION("demo", handler),
+    JERRYX_PROPERTY_LIST_END(),
   };
 
   jerry_value_t global = jerry_current_realm ();
@@ -362,7 +362,7 @@ longer needed.
 
 ```c
 jerry_value_t
-jerryx_register_global (const char *name_p,
+jerryx_register_global (jerry_value_t function_name_val,
                         jerry_external_handler_t handler_p);
 ```
 
@@ -381,14 +381,15 @@ jerryx_register_global (const char *name_p,
 #include "jerryscript-ext/properties.h"
 
 static const struct {
-  const char *name_p;
+  const jerry_char_t *name_p;
+  jerry_size_t name_size;
   jerry_external_handler_t handler_p;
 } common_functions[] =
 {
-  { "assert", jerryx_handler_assert },
-  { "gc", jerryx_handler_gc },
-  { "print", jerryx_handler_print },
-  { NULL, NULL }
+  { JERRY_ZSTR_ARG ("assert"), jerryx_handler_assert },
+  { JERRY_ZSTR_ARG ("gc"), jerryx_handler_gc },
+  { JERRY_ZSTR_ARG ("print"), jerryx_handler_print },
+  { NULL, 0, NULL }
 };
 
 static void
@@ -398,7 +399,7 @@ register_common_functions (void)
 
   for (int i = 0; common_functions[i].name_p != NULL && !jerry_value_is_exception (ret); i++)
   {
-    ret = jerryx_register_global (common_functions[i].name_p,
+    ret = jerryx_register_global (jerry_string_ascii (common_functions[i].name_p, common_functions[i].name_size),
                                   common_functions[i].handler_p);
   }
 
diff --git a/docs/11.EXT-REFERENCE-AUTORELEASE.md b/docs/11.EXT-REFERENCE-AUTORELEASE.md
index 7d46247e48..17607d1d9f 100644
--- a/docs/11.EXT-REFERENCE-AUTORELEASE.md
+++ b/docs/11.EXT-REFERENCE-AUTORELEASE.md
@@ -21,7 +21,7 @@ using the `__cleanup__` variable attribute. For other compilers, no support has
 static void
 foo (bool enable)
 {
-  JERRYX_AR_VALUE_T bar = jerry_string_sz ("...");
+  JERRYX_AR_VALUE_T bar = jerry_sz_ascii ("...");
 
   if (enable)
   {
diff --git a/docs/16.MIGRATION-GUIDE.md b/docs/16.MIGRATION-GUIDE.md
index 553330cb1b..c175c0bf48 100644
--- a/docs/16.MIGRATION-GUIDE.md
+++ b/docs/16.MIGRATION-GUIDE.md
@@ -38,6 +38,8 @@ For more information on the current API methods please check the [API reference]
 - `jerry_get_value_without_error_flag` replaced by `jerry_get_value_from_error`
 - `jerry_parse_and_save_snapshot` replaced by `jerry_generate_snapshot`
 - `jerry_parse_and_save_function_snapshot` replaced by `jerry_generate_function_snapshot`
+- `jerry_string_external_sz` replaced by `jerry_string_external`
+- `jerry_string_sz` replaced by `jerry_sz_ascii` or `jerry_string_cesu8`
 
 
 ***Removed unused configuration macros***
diff --git a/jerry-core/api/jerry-module.c b/jerry-core/api/jerry-module.c
index c0443866a8..9f0488045c 100644
--- a/jerry-core/api/jerry-module.c
+++ b/jerry-core/api/jerry-module.c
@@ -16,7 +16,7 @@
 #include "jerryscript-core.h"
 #include "jerryscript-port.h"
 
-#include "ecma-errors.h"
+#include "ecma-globals.h"
 
 #include "lit-magic-strings.h"
 #include "lit-strings.h"
@@ -162,7 +162,7 @@ jerry_module_resolve (const jerry_value_t specifier, /**< module specifier strin
 
   if (path_p == NULL)
   {
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Failed to resolve module");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Failed to resolve module"));
   }
 
   jerry_value_t realm = jerry_current_realm ();
@@ -192,7 +192,7 @@ jerry_module_resolve (const jerry_value_t specifier, /**< module specifier strin
     jerry_value_free (realm);
     jerry_port_path_free (path_p);
 
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Module file not found");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Module file not found"));
   }
 
   jerry_parse_options_t parse_options;
diff --git a/jerry-core/api/jerry-snapshot.c b/jerry-core/api/jerry-snapshot.c
index 33760b299f..2f4e194971 100644
--- a/jerry-core/api/jerry-snapshot.c
+++ b/jerry-core/api/jerry-snapshot.c
@@ -140,7 +140,7 @@ snapshot_add_compiled_code (const ecma_compiled_code_t *compiled_code_p, /**< co
                             size_t snapshot_buffer_size, /**< snapshot buffer size */
                             snapshot_globals_t *globals_p) /**< snapshot globals */
 {
-  const char *error_buffer_too_small_p = "Snapshot buffer too small";
+#define error_buffer_too_small_p "Snapshot buffer too small"
 
   if (!ecma_is_value_empty (globals_p->snapshot_error))
   {
@@ -180,7 +180,7 @@ snapshot_add_compiled_code (const ecma_compiled_code_t *compiled_code_p, /**< co
     /* Regular expression. */
     if (globals_p->snapshot_buffer_write_offset + sizeof (ecma_compiled_code_t) > snapshot_buffer_size)
     {
-      globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, error_buffer_too_small_p);
+      globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii (error_buffer_too_small_p));
       return 0;
     }
 
@@ -201,7 +201,7 @@ snapshot_add_compiled_code (const ecma_compiled_code_t *compiled_code_p, /**< co
                                              buffer_p,
                                              buffer_size))
     {
-      globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, error_buffer_too_small_p);
+      globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii (error_buffer_too_small_p));
       /* cannot return inside ECMA_FINALIZE_UTF8_STRING */
     }
 
@@ -235,7 +235,7 @@ snapshot_add_compiled_code (const ecma_compiled_code_t *compiled_code_p, /**< co
                                            compiled_code_p,
                                            ((size_t) compiled_code_p->size) << JMEM_ALIGNMENT_LOG))
   {
-    globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, error_buffer_too_small_p);
+    globals_p->snapshot_error = jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii (error_buffer_too_small_p));
     return 0;
   }
 
diff --git a/jerry-core/api/jerryscript.c b/jerry-core/api/jerryscript.c
index 60f8023fd0..354e5b3aa2 100644
--- a/jerry-core/api/jerryscript.c
+++ b/jerry-core/api/jerryscript.c
@@ -2349,6 +2349,19 @@ jerry_value_free (jerry_value_t value) /**< value */
   ecma_free_value (value);
 } /* jerry_value_free */
 
+/**
+ * Release ownership of the argument value list
+ */
+void
+jerry_value_list_free (const jerry_value_t *value_list, /**< value list */
+                       jerry_size_t value_list_count) /**< value list count */
+{
+  for (jerry_size_t i = 0; i < value_list_count; i += 1)
+  {
+    jerry_value_free (value_list[i]);
+  }
+} /* jerry_value_list_free */
+
 /**
  * Create an array object value
  *
@@ -2391,39 +2404,22 @@ jerry_error (jerry_error_t error_type, /**< type of error */
 {
   jerry_assert_api_enabled ();
 
-  ecma_string_t *message_p = NULL;
-  if (ecma_is_value_string (message))
-  {
-    message_p = ecma_get_string_from_value (message);
-  }
-
-  ecma_object_t *error_object_p = ecma_new_standard_error ((jerry_error_t) error_type, message_p);
-
-  return ecma_make_object_value (error_object_p);
+  return ecma_error_value (error_type, message);
 } /* jerry_error */
 
 /**
- * Create an Error object with a zero-terminated string as a message. If the message string is NULL, the created error
- * will not have a message property.
- *
+ * Create an Error object with the provided string value as the error `message`.
+ * If the `message` value is not a string, the created error will not have a `message` property.
+ * The `message` will be freed in this function.
  * @return Error object
  */
 jerry_value_t
 jerry_error_sz (jerry_error_t error_type, /**< type of error */
-                const char *message_p) /**< value of 'message' property
-                                        *   of constructed error object */
+                const jerry_value_t message) /**< message of the error that will be free/take */
 {
-  jerry_value_t message = ECMA_VALUE_UNDEFINED;
-
-  if (message_p != NULL)
-  {
-    message = jerry_string_sz (message_p);
-  }
-
-  ecma_value_t error = jerry_error (error_type, message);
-  ecma_free_value (message);
+  jerry_assert_api_enabled ();
 
-  return error;
+  return ecma_error_value_taked (error_type, message);
 } /* jerry_error_sz */
 
 /**
@@ -2440,17 +2436,18 @@ jerry_throw (jerry_error_t error_type, /**< type of error */
 } /* jerry_throw */
 
 /**
- * Create an exception by constructing an Error object with the specified type and the provided zero-terminated ASCII
- * string as the error message.  If the message string is NULL, the created error will not have a message property.
+ * Create an exception by constructing an Error object with the specified type and the
+ * provided string value as the error message. If the message value is not a string,
+ * the created error will not have a message property.
+ * The message will be freed in this function.
  *
  * @return exception value
  */
 jerry_value_t
 jerry_throw_sz (jerry_error_t error_type, /**< type of error */
-                const char *message_p) /**< value of 'message' property
-                                        *   of constructed error object */
+                const jerry_value_t message) /**< message of the error that will be free/take */
 {
-  return jerry_throw_value (jerry_error_sz (error_type, message_p), true);
+  return jerry_throw_value (jerry_error_sz (error_type, message), true);
 } /* jerry_throw_sz */
 
 /**
@@ -2657,23 +2654,66 @@ jerry_proxy_custom (const jerry_value_t target, /**< target argument */
 } /* jerry_proxy_custom */
 
 /**
- * Create string value from the input zero-terminated ASCII string.
+ * Create a string value from the input buffer using the ASCII encoding.
+ * The content of the buffer is assumed to be valid in the ASCII encoding,
+ * it's the callers responsibility to validate the input.
+ *
+ * See also: lit_is_valid_ascii_string
+ *
+ * @return created string
+ */
+jerry_value_t
+jerry_string_ascii (const jerry_char_t *buffer_p, /**< pointer to buffer */
+                    jerry_size_t buffer_size) /**< buffer size */
+{
+  jerry_assert_api_enabled ();
+  JERRY_ASSERT (lit_is_valid_ascii_string (buffer_p, buffer_size));
+  return ecma_make_string_value (ecma_new_ecma_string_from_ascii (buffer_p, buffer_size));
+} /* jerry_string_ascii */
+
+/**
+ * Create a string value from the input buffer using the CESU-8 encoding.
+ * The content of the buffer is assumed to be valid in the CESU-8 encoding,
+ * it's the callers responsibility to validate the input.
+ *
+ * See also: lit_is_valid_cesu8_string
+ *
+ * @return created string
+ */
+jerry_value_t
+jerry_string_cesu8 (const jerry_char_t *buffer_p, /**< pointer to buffer */
+                    jerry_size_t buffer_size) /**< buffer size */
+{
+  jerry_assert_api_enabled ();
+  JERRY_ASSERT (lit_is_valid_cesu8_string (buffer_p, buffer_size));
+  return ecma_make_string_value (ecma_new_ecma_string_from_utf8 (buffer_p, buffer_size));
+
+} /* jerry_string_cesu8 */
+
+/**
+ * Create a string value from the input buffer using the UTF-8 encoding.
+ * The content of the buffer is assumed to be valid in the UTF-8 encoding,
+ * it's the callers responsibility to validate the input.
+ *
+ * See also: lit_is_valid_utf8_string
  *
  * @return created string
  */
 jerry_value_t
-jerry_string_sz (const char *str_p) /**< pointer to string */
+jerry_string_utf8 (const jerry_char_t *buffer_p, /**< pointer to buffer */
+                   jerry_size_t buffer_size) /**< buffer size */
 {
-  const jerry_char_t *data_p = (const jerry_char_t *) str_p;
-  return jerry_string (data_p, lit_zt_utf8_string_size (data_p), JERRY_ENCODING_CESU8);
-} /* jerry_string_sz */
+  jerry_assert_api_enabled ();
+  JERRY_ASSERT (lit_is_valid_utf8_string (buffer_p, buffer_size, true));
+  return ecma_make_string_value (ecma_new_ecma_string_from_utf8_converted_to_cesu8 (buffer_p, buffer_size));
+} /* jerry_string_utf8 */
 
 /**
  * Create a string value from the input buffer using the specified encoding.
  * The content of the buffer is assumed to be valid in the specified encoding, it's the callers responsibility to
  * validate the input.
  *
- * See also: jerry_validate_string
+ * See also: jerry_string_ascii jerry_string_cesu8 jerry_string_utf8
  *
  * @return created string
  */
@@ -2682,50 +2722,34 @@ jerry_string (const jerry_char_t *buffer_p, /**< pointer to buffer */
               jerry_size_t buffer_size, /**< buffer size */
               jerry_encoding_t encoding) /**< buffer encoding */
 {
-  jerry_assert_api_enabled ();
-  ecma_string_t *ecma_str_p = NULL;
-  JERRY_ASSERT (jerry_validate_string (buffer_p, buffer_size, encoding));
-
   switch (encoding)
   {
+    case JERRY_ENCODING_ASCII:
+    {
+      return jerry_string_ascii (buffer_p, buffer_size);
+    }
     case JERRY_ENCODING_CESU8:
     {
-      ecma_str_p = ecma_new_ecma_string_from_utf8 (buffer_p, buffer_size);
-      break;
+      return jerry_string_cesu8 (buffer_p, buffer_size);
     }
     case JERRY_ENCODING_UTF8:
     {
-      ecma_str_p = ecma_new_ecma_string_from_utf8_converted_to_cesu8 (buffer_p, buffer_size);
-      break;
+      return jerry_string_utf8 (buffer_p, buffer_size);
     }
     default:
     {
+      jerry_assert_api_enabled ();
       return jerry_throw_sz (JERRY_ERROR_TYPE, ecma_get_error_msg (ECMA_ERR_INVALID_ENCODING));
     }
   }
-
-  return ecma_make_string_value (ecma_str_p);
 } /* jerry_string */
 
-/**
- * Create external string from input zero-terminated ASCII string.
- *
- * @return created external string
- */
-jerry_value_t
-jerry_string_external_sz (const char *str_p, /**< pointer to string */
-                          void *user_p) /**< user pointer passed to the callback when the string is freed */
-{
-  const jerry_char_t *data_p = (const jerry_char_t *) str_p;
-  return jerry_string_external (data_p, lit_zt_utf8_string_size (data_p), user_p);
-} /* jerry_string_external_sz */
-
 /**
  * Create external string from a valid CESU-8 encoded string.
  * The content of the buffer is assumed be encoded correctly, it's the callers responsibility to
  * validate the input.
  *
- * See also: jerry_validate_string
+ * See also: lit_is_valid_cesu8_string
  *
  * @return created external string
  */
@@ -2736,7 +2760,7 @@ jerry_string_external (const jerry_char_t *buffer_p, /**< pointer to string */
 {
   jerry_assert_api_enabled ();
 
-  JERRY_ASSERT (jerry_validate_string (buffer_p, buffer_size, JERRY_ENCODING_CESU8));
+  JERRY_ASSERT (lit_is_valid_cesu8_string (buffer_p, buffer_size));
   ecma_string_t *ecma_str_p = ecma_new_ecma_external_string_from_cesu8 (buffer_p, buffer_size, user_p);
   return ecma_make_string_value (ecma_str_p);
 } /* jerry_string_external_sz_sz */
@@ -2790,18 +2814,20 @@ jerry_bigint (const uint64_t *digits_p, /**< BigInt digits (lowest digit first)
 /**
  * Creates a RegExp object with the given ASCII pattern and flags.
  *
+ * Note:
+ *      `pattern_sz` will be freed in this function
+ *
  * @return value of the constructed RegExp object.
  */
 jerry_value_t
-jerry_regexp_sz (const char *pattern_p, /**< RegExp pattern as zero-terminated ASCII string */
+jerry_regexp_sz (const jerry_value_t pattern_sz, /**< RegExp pattern string that will be free/take */
                  uint16_t flags) /**< RegExp flags */
 {
   jerry_assert_api_enabled ();
 
-  jerry_value_t pattern = jerry_string_sz (pattern_p);
-  jerry_value_t result = jerry_regexp (pattern, flags);
+  jerry_value_t result = jerry_regexp (pattern_sz, flags);
 
-  jerry_value_free (pattern);
+  jerry_value_free (pattern_sz);
   return jerry_return (result);
 } /* jerry_regexp_sz */
 
@@ -3135,18 +3161,20 @@ jerry_object_has (const jerry_value_t object, /**< object value */
 /**
  * Checks whether the object or it's prototype objects have the given property.
  *
+ * Note:
+ *      `key_sz` will be freed in this function
+ *
  * @return raised error - if the operation fail
  *         true/false API value  - depend on whether the property exists
  */
 jerry_value_t
 jerry_object_has_sz (const jerry_value_t object, /**< object value */
-                     const char *key_p) /**< property key */
+                     const jerry_value_t key_sz) /**< property key that will be free/take */
 {
   jerry_assert_api_enabled ();
 
-  jerry_value_t key_str = jerry_string_sz (key_p);
-  jerry_value_t result = jerry_object_has (object, key_str);
-  ecma_free_value (key_str);
+  jerry_value_t result = jerry_object_has (object, key_sz);
+  ecma_free_value (key_sz);
 
   return result;
 } /* jerry_object_has */
@@ -3236,18 +3264,20 @@ jerry_object_delete (jerry_value_t object, /**< object value */
 /**
  * Delete a property from an object.
  *
+ * Note:
+ *      `key_sz` will be freed in this function
+ *
  * @return boolean value - wether the property was deleted successfully
  *         exception - otherwise
  */
 jerry_value_t
 jerry_object_delete_sz (jerry_value_t object, /**< object value */
-                        const char *key_p) /**< property key */
+                        const jerry_value_t key_sz) /**< property name that will be free/take*/
 {
   jerry_assert_api_enabled ();
 
-  jerry_value_t key_str = jerry_string_sz (key_p);
-  jerry_value_t result = jerry_object_delete (object, key_str);
-  ecma_free_value (key_str);
+  jerry_value_t result = jerry_object_delete (object, key_sz);
+  ecma_free_value (key_sz);
 
   return result;
 } /* jerry_object_delete */
@@ -3351,6 +3381,7 @@ jerry_object_get (const jerry_value_t object, /**< object value */
  * Get value of a property to the specified object with the given name.
  *
  * Note:
+ *      `key_sz` will be freed in this function
  *      returned value must be freed with jerry_value_free, when it is no longer needed.
  *
  * @return value of the property - if success
@@ -3358,13 +3389,12 @@ jerry_object_get (const jerry_value_t object, /**< object value */
  */
 jerry_value_t
 jerry_object_get_sz (const jerry_value_t object, /**< object value */
-                     const char *key_p) /**< property key */
+                     const jerry_value_t key_sz) /**< property key that will be free/take */
 {
   jerry_assert_api_enabled ();
 
-  jerry_value_t key_str = jerry_string_sz (key_p);
-  jerry_value_t result = jerry_object_get (object, key_str);
-  ecma_free_value (key_str);
+  jerry_value_t result = jerry_object_get (object, key_sz);
+  ecma_free_value (key_sz);
 
   return result;
 } /* jerry_object_get */
@@ -3529,6 +3559,7 @@ jerry_object_set (jerry_value_t object, /**< object value */
  * Set a property to the specified object with the given name.
  *
  * Note:
+ *      `key_sz` will be freed in this function
  *      returned value must be freed with jerry_value_free, when it is no longer needed.
  *
  * @return true value - if the operation was successful
@@ -3536,14 +3567,13 @@ jerry_object_set (jerry_value_t object, /**< object value */
  */
 jerry_value_t
 jerry_object_set_sz (jerry_value_t object, /**< object value */
-                     const char *key_p, /**< property key */
+                     const jerry_value_t key_sz, /**< property key that will be free/take */
                      const jerry_value_t value) /**< value to set */
 {
   jerry_assert_api_enabled ();
 
-  jerry_value_t key_str = jerry_string_sz (key_p);
-  jerry_value_t result = jerry_object_set (object, key_str, value);
-  ecma_free_value (key_str);
+  jerry_value_t result = jerry_object_set (object, key_sz, value);
+  ecma_free_value (key_sz);
 
   return result;
 } /* jerry_object_set */
@@ -5045,6 +5075,10 @@ jerry_validate_string (const jerry_char_t *buffer_p, /**< string buffer */
 {
   switch (encoding)
   {
+    case JERRY_ENCODING_ASCII:
+    {
+      return lit_is_valid_ascii_string (buffer_p, buffer_size);
+    }
     case JERRY_ENCODING_CESU8:
     {
       return lit_is_valid_cesu8_string (buffer_p, buffer_size);
@@ -5082,49 +5116,33 @@ jerry_log_set_level (jerry_log_level_t level)
  * Log a zero-terminated string message.
  *
  * @param str_p: message
+ * @param str_size: size of message
  */
 static void
-jerry_log_string (const char *str_p)
+jerry_log_string (const jerry_char_t *str_p, jerry_size_t str_size)
 {
-  jerry_port_log (str_p);
+  jerry_port_log_buffer (str_p, str_size);
 
 #if JERRY_DEBUGGER
   if (jerry_debugger_is_connected ())
   {
-    jerry_debugger_send_string (JERRY_DEBUGGER_OUTPUT_RESULT,
-                                JERRY_DEBUGGER_OUTPUT_LOG,
-                                (const uint8_t *) str_p,
-                                strlen (str_p));
+    jerry_debugger_send_string (JERRY_DEBUGGER_OUTPUT_RESULT, JERRY_DEBUGGER_OUTPUT_LOG, str_p, str_size);
   }
 #endif /* JERRY_DEBUGGER */
 } /* jerry_log_string */
 
 /**
- * Log a fixed-size string message.
+ * Log a zero-terminated number string message.
  *
- * @param str_p: message
- * @param size: size
- * @param buffer_p: buffer to use
+ * @param cursor_p: the number string cursor
+ * @param buffer_p: buffer used to construct the number string
  */
 static void
-jerry_log_string_fixed (const char *str_p, size_t size, char *buffer_p)
+jerry_log_cursor (const jerry_char_t *cursor_p, jerry_char_t *buffer_p)
 {
-  const size_t batch_size = JERRY_LOG_BUFFER_SIZE - 1;
-
-  while (size > batch_size)
-  {
-    memcpy (buffer_p, str_p, batch_size);
-    buffer_p[batch_size] = '\0';
-    jerry_log_string (buffer_p);
-
-    str_p += batch_size;
-    size -= batch_size;
-  }
-
-  memcpy (buffer_p, str_p, size);
-  buffer_p[size] = '\0';
-  jerry_log_string (buffer_p);
-} /* jerry_log_string_fixed */
+  jerry_char_t *tail_p = buffer_p + JERRY_LOG_BUFFER_SIZE - 1;
+  jerry_log_string (cursor_p, (jerry_size_t) (tail_p - cursor_p));
+} /* jerry_log_cursor */
 
 /**
  * Format an unsigned number.
@@ -5137,11 +5155,13 @@ jerry_log_string_fixed (const char *str_p, size_t size, char *buffer_p)
  *
  * @return formatted number as string
  */
-static char *
-jerry_format_unsigned (unsigned int num, uint8_t width, char padding, uint8_t radix, char *buffer_p)
+static jerry_char_t *
+jerry_format_unsigned (unsigned int num, uint8_t width, jerry_char_t padding, uint8_t radix, jerry_char_t *buffer_p)
 {
-  static const char digits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
-  char *cursor_p = buffer_p + JERRY_LOG_BUFFER_SIZE;
+  static const jerry_char_t digits[] = {
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+  };
+  jerry_char_t *cursor_p = buffer_p + JERRY_LOG_BUFFER_SIZE;
   *(--cursor_p) = '\0';
   uint8_t count = 0;
 
@@ -5171,8 +5191,8 @@ jerry_format_unsigned (unsigned int num, uint8_t width, char padding, uint8_t ra
  *
  * @return formatted number as string
  */
-static char *
-jerry_format_int (int num, uint8_t width, char padding, char *buffer_p)
+static jerry_char_t *
+jerry_format_int (int num, uint8_t width, jerry_char_t padding, jerry_char_t *buffer_p)
 {
   if (num >= 0)
   {
@@ -5183,15 +5203,15 @@ jerry_format_int (int num, uint8_t width, char padding, char *buffer_p)
 
   if (padding == '0' && width > 0)
   {
-    char *cursor_p = jerry_format_unsigned ((unsigned) num, --width, padding, 10, buffer_p);
+    jerry_char_t *cursor_p = jerry_format_unsigned ((unsigned) num, --width, padding, 10, buffer_p);
     *(--cursor_p) = '-';
     return cursor_p;
   }
 
-  char *cursor_p = jerry_format_unsigned ((unsigned) num, 0, ' ', 10, buffer_p);
+  jerry_char_t *cursor_p = jerry_format_unsigned ((unsigned) num, 0, ' ', 10, buffer_p);
   *(--cursor_p) = '-';
 
-  char *indent_p = buffer_p + JERRY_LOG_BUFFER_SIZE - width - 1;
+  jerry_char_t *indent_p = buffer_p + JERRY_LOG_BUFFER_SIZE - width - 1;
 
   while (cursor_p > indent_p)
   {
@@ -5225,9 +5245,9 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
   }
 
   va_list vl;
-  char buffer_p[JERRY_LOG_BUFFER_SIZE];
-  uint32_t buffer_index = 0;
-  const char *cursor_p = format_p;
+  jerry_char_t buffer_p[JERRY_LOG_BUFFER_SIZE];
+  jerry_size_t buffer_index = 0;
+  const jerry_char_t *cursor_p = (const jerry_char_t *) format_p;
   va_start (vl, format_p);
 
   while (*cursor_p != '\0')
@@ -5235,7 +5255,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     if (*cursor_p == '%' || buffer_index > JERRY_LOG_BUFFER_SIZE - 2)
     {
       buffer_p[buffer_index] = '\0';
-      jerry_log_string (buffer_p);
+      jerry_log_string (buffer_p, buffer_index);
       buffer_index = 0;
     }
 
@@ -5247,8 +5267,8 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
 
     ++cursor_p;
     uint8_t width = 0;
-    size_t precision = 0;
-    char padding = ' ';
+    jerry_size_t precision = 0;
+    jerry_char_t padding = ' ';
 
     if (*cursor_p == '0')
     {
@@ -5268,7 +5288,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     }
     else if (*cursor_p == '.' && *(cursor_p + 1) == '*')
     {
-      precision = (size_t) va_arg (vl, int);
+      precision = (jerry_size_t) va_arg (vl, int);
       cursor_p += 2;
     }
 
@@ -5283,36 +5303,59 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     {
       case 's':
       {
-        char *str_p = va_arg (vl, char *);
+        jerry_char_t *str_p = va_arg (vl, jerry_char_t *);
 
         if (precision == 0)
         {
-          jerry_log_string (str_p);
+          jerry_log_string (str_p, (jerry_size_t) strlen ((const char *) str_p));
           break;
         }
 
-        jerry_log_string_fixed (str_p, precision, buffer_p);
+        jerry_log_string (str_p, precision);
+        break;
+      }
+      case 'S':
+      {
+        jerry_value_t str = va_arg (vl, jerry_value_t);
+        ecma_string_t *string2_p = ecma_op_to_string (str);
+        lit_utf8_size_t cesu8_string2_size;
+        lit_utf8_size_t cesu8_string2_length;
+        lit_utf8_byte_t uint32_to_string_buffer[ECMA_MAX_CHARS_IN_STRINGIFIED_UINT32];
+        uint8_t flags = ECMA_STRING_FLAG_EMPTY;
+
+        const lit_utf8_byte_t *cesu8_string2_p = ecma_string_get_chars (string2_p,
+                                                                        &cesu8_string2_size,
+                                                                        &cesu8_string2_length,
+                                                                        uint32_to_string_buffer,
+                                                                        &flags);
+        jerry_log_string (cesu8_string2_p, cesu8_string2_size);
+        if (flags & ECMA_STRING_FLAG_MUST_BE_FREED)
+        {
+          jmem_heap_free_block ((void *) cesu8_string2_p, cesu8_string2_size);
+        }
+
+        ecma_deref_ecma_string (string2_p);
         break;
       }
       case 'c':
       {
         /* Arguments of types narrower than int are promoted to int for variadic functions */
-        buffer_p[buffer_index++] = (char) va_arg (vl, int);
+        buffer_p[buffer_index++] = (jerry_char_t) va_arg (vl, int);
         break;
       }
       case 'd':
       {
-        jerry_log_string (jerry_format_int (va_arg (vl, int), width, padding, buffer_p));
+        jerry_log_cursor (jerry_format_int (va_arg (vl, int), width, padding, buffer_p), buffer_p);
         break;
       }
       case 'u':
       {
-        jerry_log_string (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 10, buffer_p));
+        jerry_log_cursor (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 10, buffer_p), buffer_p);
         break;
       }
       case 'x':
       {
-        jerry_log_string (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 16, buffer_p));
+        jerry_log_cursor (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 16, buffer_p), buffer_p);
         break;
       }
       default:
@@ -5326,7 +5369,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
   if (buffer_index > 0)
   {
     buffer_p[buffer_index] = '\0';
-    jerry_log_string (buffer_p);
+    jerry_log_string (buffer_p, buffer_index);
   }
 
   va_end (vl);
diff --git a/jerry-core/debugger/debugger.c b/jerry-core/debugger/debugger.c
index 2d77f88328..5715f8cf19 100644
--- a/jerry-core/debugger/debugger.c
+++ b/jerry-core/debugger/debugger.c
@@ -596,7 +596,7 @@ jerry_debugger_send_eval (const lit_utf8_byte_t *eval_string_p, /**< evaluated s
         ecma_free_value (result);
 
         const lit_utf8_byte_t *string_p = lit_get_magic_string_utf8 (id);
-        jerry_debugger_send_string (JERRY_DEBUGGER_EVAL_RESULT, type, string_p, strlen ((const char *) string_p));
+        jerry_debugger_send_string (JERRY_DEBUGGER_EVAL_RESULT, type, string_p, lit_get_magic_string_size (id));
         return false;
       }
     }
@@ -1482,15 +1482,17 @@ jerry_debugger_exception_object_to_string (ecma_value_t exception_obj_value) /**
 
   ecma_property_value_t *prop_value_p = ECMA_PROPERTY_VALUE_PTR (property_p);
 
-  if (!ecma_is_value_string (prop_value_p->value))
+  if (ecma_is_value_string (prop_value_p->value))
   {
-    return ecma_stringbuilder_finalize (&builder);
+    ecma_string_t *string_p = ecma_get_string_from_value (prop_value_p->value);
+    if (!ecma_string_is_empty (string_p))
+    {
+      ecma_stringbuilder_append_byte (&builder, LIT_CHAR_COLON);
+      ecma_stringbuilder_append_byte (&builder, LIT_CHAR_SP);
+      ecma_stringbuilder_append (&builder, string_p);
+    }
   }
 
-  ecma_stringbuilder_append_byte (&builder, LIT_CHAR_COLON);
-  ecma_stringbuilder_append_byte (&builder, LIT_CHAR_SP);
-  ecma_stringbuilder_append (&builder, ecma_get_string_from_value (prop_value_p->value));
-
   return ecma_stringbuilder_finalize (&builder);
 } /* jerry_debugger_exception_object_to_string */
 
diff --git a/jerry-core/ecma/base/ecma-errors.c b/jerry-core/ecma/base/ecma-errors.c
index 7592fe829b..5212bc5257 100644
--- a/jerry-core/ecma/base/ecma-errors.c
+++ b/jerry-core/ecma/base/ecma-errors.c
@@ -15,6 +15,9 @@
 
 #include "ecma-errors.h"
 
+#include "ecma-globals.h"
+#include "ecma-helpers.h"
+
 #if JERRY_ERROR_MESSAGES
 /**
  * Struct to store ecma error message with its size.
@@ -37,35 +40,21 @@ static ecma_error_message_t ecma_error_messages[] JERRY_ATTR_CONST_DATA = {
 #endif /* JERRY_ERROR_MESSAGES */
 
 /**
- * Get specified ecma error as zero-terminated string
+ * Get error string of specified ecma error
  *
- * @return pointer to zero-terminated ecma error
+ * @return created string for ecma error
  */
-const char *
+ecma_value_t
 ecma_get_error_msg (ecma_error_msg_t id) /**< ecma error id */
 {
   JERRY_ASSERT (id != ECMA_IS_VALID_CONSTRUCTOR);
-
+  ecma_string_t *ecma_str_p;
 #if JERRY_ERROR_MESSAGES
-  return ecma_error_messages[id].text;
+  ecma_error_message_t *msg = ecma_error_messages + id;
+  JERRY_ASSERT (lit_is_valid_ascii_string ((const lit_utf8_byte_t *) msg->text, msg->size));
+  ecma_str_p = ecma_new_ecma_string_from_ascii ((const lit_utf8_byte_t *) msg->text, msg->size);
 #else /* !JERRY_ERROR_MESSAGES */
-  return NULL;
+  ecma_str_p = ecma_get_magic_string (LIT_MAGIC_STRING__EMPTY);
 #endif /* JERRY_ERROR_MESSAGES */
+  return ecma_make_string_value (ecma_str_p);
 } /* ecma_get_error_msg */
-
-/**
- * Get size of specified ecma error
- *
- * @return size in bytes
- */
-lit_utf8_size_t
-ecma_get_error_size (ecma_error_msg_t id) /**< ecma error id */
-{
-  JERRY_ASSERT (id != ECMA_IS_VALID_CONSTRUCTOR);
-
-#if JERRY_ERROR_MESSAGES
-  return ecma_error_messages[id].size;
-#else /* !JERRY_ERROR_MESSAGES */
-  return 0;
-#endif /* JERRY_ERROR_MESSAGES */
-} /* ecma_get_error_size */
diff --git a/jerry-core/ecma/base/ecma-errors.h b/jerry-core/ecma/base/ecma-errors.h
index 72947e6e69..2880992cbe 100644
--- a/jerry-core/ecma/base/ecma-errors.h
+++ b/jerry-core/ecma/base/ecma-errors.h
@@ -33,7 +33,4 @@ typedef enum
   ECMA_IS_VALID_CONSTRUCTOR /* used as return value when checking constructor */
 } ecma_error_msg_t;
 
-const char* ecma_get_error_msg (ecma_error_msg_t id);
-lit_utf8_size_t ecma_get_error_size (ecma_error_msg_t id);
-
 #endif /* !ECMA_ERRORS_H */
diff --git a/jerry-core/ecma/base/ecma-globals.h b/jerry-core/ecma/base/ecma-globals.h
index 75c70e196b..4d89719dd9 100644
--- a/jerry-core/ecma/base/ecma-globals.h
+++ b/jerry-core/ecma/base/ecma-globals.h
@@ -2264,6 +2264,8 @@ typedef enum
  */
 #define ECMA_PRIVATE_PROPERTY_KIND(prop) ((prop) & ((ECMA_PRIVATE_PROPERTY_STATIC_FLAG - 1)))
 
+ecma_value_t ecma_get_error_msg (ecma_error_msg_t id);
+
 /**
  * @}
  * @}
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-async-from-sync-iterator-prototype.c b/jerry-core/ecma/builtin-objects/ecma-builtin-async-from-sync-iterator-prototype.c
index 43308c86a6..161aaaca35 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-async-from-sync-iterator-prototype.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-async-from-sync-iterator-prototype.c
@@ -252,27 +252,14 @@ ecma_builtin_async_from_sync_iterator_prototype_do (ecma_async_from_sync_iterato
   {
     ecma_free_value (call_result);
 
-#if JERRY_ERROR_MESSAGES
-    const lit_utf8_byte_t *msg_p = (lit_utf8_byte_t *) ecma_get_error_msg (ECMA_ERR_ARGUMENT_IS_NOT_AN_OBJECT);
-    lit_utf8_size_t msg_size = ecma_get_error_size (ECMA_ERR_ARGUMENT_IS_NOT_AN_OBJECT);
-    ecma_string_t *error_msg_p = ecma_new_ecma_string_from_ascii (msg_p, msg_size);
-#else /* !JERRY_ERROR_MESSAGES */
-    ecma_string_t *error_msg_p = ecma_get_magic_string (LIT_MAGIC_STRING__EMPTY);
-#endif /* JERRY_ERROR_MESSAGES */
-
-    ecma_object_t *type_error_obj_p = ecma_new_standard_error (JERRY_ERROR_TYPE, error_msg_p);
-
-#if JERRY_ERROR_MESSAGES
-    ecma_deref_ecma_string (error_msg_p);
-#endif /* JERRY_ERROR_MESSAGES */
-
-    ecma_value_t type_error = ecma_make_object_value (type_error_obj_p);
+    ecma_value_t type_error =
+      ecma_error_value_taked (JERRY_ERROR_TYPE, ecma_get_error_msg (ECMA_ERR_ARGUMENT_IS_NOT_AN_OBJECT));
 
     /* 10.a. */
     ecma_value_t reject =
       ecma_op_function_call (ecma_get_object_from_value (capability_p->reject), ECMA_VALUE_UNDEFINED, &type_error, 1);
     JERRY_ASSERT (!ECMA_IS_VALUE_ERROR (reject));
-    ecma_deref_object (type_error_obj_p);
+    ecma_free_value (type_error);
     ecma_free_value (reject);
 
     /* 10.b. */
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-async-generator-prototype.c b/jerry-core/ecma/builtin-objects/ecma-builtin-async-generator-prototype.c
index 474bd87740..0ec06071e5 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-async-generator-prototype.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-async-generator-prototype.c
@@ -109,16 +109,11 @@ ecma_builtin_async_generator_prototype_dispatch_routine (uint8_t builtin_routine
 
   if (executable_object_p == NULL)
   {
-    const char *msg_p = ecma_get_error_msg (ECMA_ERR_ARGUMENT_THIS_NOT_ASYNC_GENERATOR);
-    lit_utf8_size_t msg_size = ecma_get_error_size (ECMA_ERR_ARGUMENT_THIS_NOT_ASYNC_GENERATOR);
-    ecma_string_t *error_msg_p = ecma_new_ecma_string_from_ascii ((const lit_utf8_byte_t *) msg_p, msg_size);
-
-    ecma_object_t *type_error_obj_p = ecma_new_standard_error (JERRY_ERROR_TYPE, error_msg_p);
-    ecma_deref_ecma_string (error_msg_p);
-
+    ecma_value_t error_value =
+      ecma_error_value_taked (JERRY_ERROR_TYPE, ecma_get_error_msg (ECMA_ERR_ARGUMENT_THIS_NOT_ASYNC_GENERATOR));
     ecma_value_t promise = ecma_op_create_promise_object (ECMA_VALUE_EMPTY, ECMA_VALUE_UNDEFINED, NULL);
-    ecma_reject_promise (promise, ecma_make_object_value (type_error_obj_p));
-    ecma_deref_object (type_error_obj_p);
+    ecma_reject_promise (promise, error_value);
+    ecma_free_value (error_value);
 
     return promise;
   }
diff --git a/jerry-core/ecma/operations/ecma-exceptions.c b/jerry-core/ecma/operations/ecma-exceptions.c
index 675aaf92f9..5ea1417d21 100644
--- a/jerry-core/ecma/operations/ecma-exceptions.c
+++ b/jerry-core/ecma/operations/ecma-exceptions.c
@@ -168,6 +168,42 @@ ecma_new_standard_error (jerry_error_t error_type, /**< native error type */
   return error_object_p;
 } /* ecma_new_standard_error */
 
+/**
+ * Create an Error object with the provided string value as the error message.
+ * If the message value is not a string, the created error will not have a message property.
+ *
+ * @return Error object
+ */
+ecma_value_t
+ecma_error_value (jerry_error_t error_type, /**< type of error */
+                  ecma_value_t message) /**< message of the error */
+{
+  ecma_string_t *message_p = NULL;
+  if (ecma_is_value_string (message))
+  {
+    message_p = ecma_get_string_from_value (message);
+  }
+
+  ecma_object_t *error_object_p = ecma_new_standard_error ((jerry_error_t) error_type, message_p);
+
+  return ecma_make_object_value (error_object_p);
+} /* ecma_error_value */
+
+/**
+ * Create an Error object with the provided string value as the error message.
+ * If the message value is not a string, the created error will not have a message property.
+ * The message will be freed in this function.
+ * @return Error object
+ */
+ecma_value_t
+ecma_error_value_taked (jerry_error_t error_type, /**< type of error */
+                        ecma_value_t message) /**< message of the error that will be free/take */
+{
+  ecma_value_t error = ecma_error_value (error_type, message);
+  ecma_free_value (message);
+  return error;
+} /* ecma_error_value_taked */
+
 /**
  * aggregate-error object constructor.
  *
@@ -298,21 +334,7 @@ ecma_value_t
 ecma_raise_standard_error (jerry_error_t error_type, /**< error type */
                            ecma_error_msg_t msg) /**< error message */
 {
-  ecma_object_t *error_obj_p;
-  const lit_utf8_byte_t *str_p = (lit_utf8_byte_t *) ecma_get_error_msg (msg);
-
-  if (msg != ECMA_ERR_EMPTY)
-  {
-    ecma_string_t *error_msg_p = ecma_new_ecma_external_string_from_cesu8 (str_p, ecma_get_error_size (msg), NULL);
-    error_obj_p = ecma_new_standard_error (error_type, error_msg_p);
-    ecma_deref_ecma_string (error_msg_p);
-  }
-  else
-  {
-    error_obj_p = ecma_new_standard_error (error_type, NULL);
-  }
-
-  jcontext_raise_exception (ecma_make_object_value (error_obj_p));
+  jcontext_raise_exception (ecma_error_value_taked (error_type, ecma_get_error_msg (msg)));
   return ECMA_VALUE_ERROR;
 } /* ecma_raise_standard_error */
 
diff --git a/jerry-core/ecma/operations/ecma-exceptions.h b/jerry-core/ecma/operations/ecma-exceptions.h
index c367a6bf5e..6935f1d86e 100644
--- a/jerry-core/ecma/operations/ecma-exceptions.h
+++ b/jerry-core/ecma/operations/ecma-exceptions.h
@@ -29,6 +29,8 @@
 
 jerry_error_t ecma_get_error_type (ecma_object_t *error_object_p);
 ecma_object_t *ecma_new_standard_error (jerry_error_t error_type, ecma_string_t *message_string_p);
+ecma_value_t ecma_error_value (jerry_error_t error_type, ecma_value_t message);
+ecma_value_t ecma_error_value_taked (jerry_error_t error_type, ecma_value_t message);
 #if JERRY_ERROR_MESSAGES
 ecma_value_t ecma_raise_standard_error_with_format (jerry_error_t error_type, const char *msg_p, ...);
 #endif /* JERRY_ERROR_MESSAGES */
diff --git a/jerry-core/include/jerryscript-compiler.h b/jerry-core/include/jerryscript-compiler.h
index 4732f010f7..41117d237e 100644
--- a/jerry-core/include/jerryscript-compiler.h
+++ b/jerry-core/include/jerryscript-compiler.h
@@ -185,6 +185,13 @@ void *__cdecl _alloca (size_t _Size);
 #define JERRY_VLA(type, name, size) type name[size]
 #endif /* !JERRY_VLA */
 
+/**
+ * Helper to make sure unused parameters, variables, or expressions trigger no compiler warning.
+ */
+#ifndef JERRY_UNUSED
+#define JERRY_UNUSED(x) ((void) (x))
+#endif /* !JERRY_UNUSED */
+
 /**
  * @}
  */
diff --git a/jerry-core/include/jerryscript-core.h b/jerry-core/include/jerryscript-core.h
index b034b10919..a03304d235 100644
--- a/jerry-core/include/jerryscript-core.h
+++ b/jerry-core/include/jerryscript-core.h
@@ -174,6 +174,7 @@ bool jerry_frame_is_strict (jerry_frame_t *frame_p);
 /* Reference management */
 jerry_value_t JERRY_ATTR_WARN_UNUSED_RESULT jerry_value_copy (const jerry_value_t value);
 void jerry_value_free (jerry_value_t value);
+void jerry_value_list_free (const jerry_value_t *value_list, jerry_size_t value_list_count);
 
 /**
  * @defgroup jerry-api-value-checks Type inspection
@@ -255,8 +256,8 @@ jerry_value_t jerry_binary_op (jerry_binary_op_t operation, const jerry_value_t
  * @defgroup jerry-api-exception-ctor Constructors
  * @{
  */
-jerry_value_t jerry_throw (jerry_error_t type, const jerry_value_t message);
-jerry_value_t jerry_throw_sz (jerry_error_t type, const char *message_p);
+jerry_value_t jerry_throw (jerry_error_t error_type, const jerry_value_t message);
+jerry_value_t jerry_throw_sz (jerry_error_t error_type, const jerry_value_t message);
 jerry_value_t jerry_throw_value (jerry_value_t value, bool take_ownership);
 jerry_value_t jerry_throw_abort (jerry_value_t value, bool take_ownership);
 /**
@@ -428,9 +429,10 @@ void jerry_bigint_to_digits (const jerry_value_t value, uint64_t *digits_p, uint
  * @{
  */
 jerry_value_t jerry_string (const jerry_char_t *buffer_p, jerry_size_t buffer_size, jerry_encoding_t encoding);
-jerry_value_t jerry_string_sz (const char *str_p);
+jerry_value_t jerry_string_ascii (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
+jerry_value_t jerry_string_cesu8 (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
+jerry_value_t jerry_string_utf8 (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
 jerry_value_t jerry_string_external (const jerry_char_t *buffer_p, jerry_size_t buffer_size, void *user_p);
-jerry_value_t jerry_string_external_sz (const char *str_p, void *user_p);
 /**
  * jerry-api-string-cotr @}
  */
@@ -550,7 +552,7 @@ bool jerry_object_foreach (const jerry_value_t object, jerry_object_property_for
  * @{
  */
 jerry_value_t jerry_object_set (jerry_value_t object, const jerry_value_t key, const jerry_value_t value);
-jerry_value_t jerry_object_set_sz (jerry_value_t object, const char *key_p, const jerry_value_t value);
+jerry_value_t jerry_object_set_sz (jerry_value_t object, const jerry_value_t key_sz, const jerry_value_t value);
 jerry_value_t jerry_object_set_index (jerry_value_t object, uint32_t index, const jerry_value_t value);
 jerry_value_t jerry_object_define_own_prop (jerry_value_t object,
                                             const jerry_value_t key,
@@ -568,7 +570,7 @@ void jerry_object_set_native_ptr (jerry_value_t object,
  * @{
  */
 jerry_value_t jerry_object_has (const jerry_value_t object, const jerry_value_t key);
-jerry_value_t jerry_object_has_sz (const jerry_value_t object, const char *key_p);
+jerry_value_t jerry_object_has_sz (const jerry_value_t object, const jerry_value_t key_sz);
 jerry_value_t jerry_object_has_own (const jerry_value_t object, const jerry_value_t key);
 bool jerry_object_has_internal (const jerry_value_t object, const jerry_value_t key);
 bool jerry_object_has_native_ptr (const jerry_value_t object, const jerry_object_native_info_t *native_info_p);
@@ -581,7 +583,7 @@ bool jerry_object_has_native_ptr (const jerry_value_t object, const jerry_object
  * @{
  */
 jerry_value_t jerry_object_get (const jerry_value_t object, const jerry_value_t key);
-jerry_value_t jerry_object_get_sz (const jerry_value_t object, const char *key_p);
+jerry_value_t jerry_object_get_sz (const jerry_value_t object, const jerry_value_t key_sz);
 jerry_value_t jerry_object_get_index (const jerry_value_t object, uint32_t index);
 jerry_value_t jerry_object_get_own_prop (const jerry_value_t object,
                                          const jerry_value_t key,
@@ -602,7 +604,7 @@ jerry_value_t jerry_object_find_own (const jerry_value_t object,
  * @{
  */
 jerry_value_t jerry_object_delete (jerry_value_t object, const jerry_value_t key);
-jerry_value_t jerry_object_delete_sz (const jerry_value_t object, const char *key_p);
+jerry_value_t jerry_object_delete_sz (const jerry_value_t object, const jerry_value_t key_sz);
 jerry_value_t jerry_object_delete_index (jerry_value_t object, uint32_t index);
 bool jerry_object_delete_internal (jerry_value_t object, const jerry_value_t key);
 bool jerry_object_delete_native_ptr (jerry_value_t object, const jerry_object_native_info_t *native_info_p);
@@ -1015,7 +1017,7 @@ jerry_value_t jerry_container_op (jerry_container_op_t operation,
  * @{
  */
 jerry_value_t jerry_regexp (const jerry_value_t pattern, uint16_t flags);
-jerry_value_t jerry_regexp_sz (const char *pattern_p, uint16_t flags);
+jerry_value_t jerry_regexp_sz (const jerry_value_t pattern_sz, uint16_t flags);
 /**
  * jerry-api-regexp-ctor @}
  */
@@ -1033,8 +1035,8 @@ jerry_value_t jerry_regexp_sz (const char *pattern_p, uint16_t flags);
  * @defgroup jerry-api-error-ctor Constructors
  * @{
  */
-jerry_value_t jerry_error (jerry_error_t type, const jerry_value_t message);
-jerry_value_t jerry_error_sz (jerry_error_t type, const char *message_p);
+jerry_value_t jerry_error (jerry_error_t error_type, const jerry_value_t message);
+jerry_value_t jerry_error_sz (jerry_error_t error_type, const jerry_value_t message);
 /**
  * jerry-api-error-ctor @}
  */
@@ -1204,6 +1206,31 @@ jerry_value_t jerry_realm_set_this (jerry_value_t realm, jerry_value_t this_valu
 
 JERRY_C_API_END
 
+/**
+ * Create string value from the zero-terminated ASCII encoded literal string.
+ * The content of the buffer is assumed be encoded correctly, it's the callers responsibility to
+ * validate the input.
+ *
+ * @return created string
+ */
+#define jerry_sz_ascii(str) jerry_string_ascii (JERRY_ZSTR_ARG (str))
+/**
+ * Create string value from the zero-terminated CESU-8 encoded literal string.
+ * The content of the buffer is assumed be encoded correctly, it's the callers responsibility to
+ * validate the input.
+ *
+ * @return created string
+ */
+#define jerry_sz_cesu8(str) jerry_string_cesu8 (JERRY_ZSTR_ARG (str))
+/**
+ * Create string value from the zero-terminated UTF-8 encoded literal string.
+ * The content of the buffer is assumed be encoded correctly, it's the callers responsibility to
+ * validate the input.
+ *
+ * @return created string
+ */
+#define jerry_sz_utf8(str) jerry_string_utf8 (JERRY_ZSTR_ARG (str))
+
 #endif /* !JERRYSCRIPT_CORE_H */
 
 /* vim: set fdm=marker fmr=@{,@}: */
diff --git a/jerry-core/include/jerryscript-port.h b/jerry-core/include/jerryscript-port.h
index 0d8b34e1d4..cb8a19ce28 100644
--- a/jerry-core/include/jerryscript-port.h
+++ b/jerry-core/include/jerryscript-port.h
@@ -139,8 +139,11 @@ void jerry_port_context_free (void);
  *
  * The implementation can decide whether error and debug messages are logged to
  * the console, or saved to a database or to a file.
+ *
+ * @param buffer_p: input buffer that is a zero-terminated UTF-8 string
+ * @param buffer_size: data size
  */
-void jerry_port_log (const char *message_p);
+void jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
 
 /**
  * Print a buffer to standard output
diff --git a/jerry-core/include/jerryscript-types.h b/jerry-core/include/jerryscript-types.h
index f0766b91ca..27c4e94916 100644
--- a/jerry-core/include/jerryscript-types.h
+++ b/jerry-core/include/jerryscript-types.h
@@ -153,6 +153,15 @@ typedef uint32_t jerry_length_t;
  */
 typedef uint32_t jerry_value_t;
 
+/**
+ * Description of a JerryScript string for arguments passing
+ */
+typedef struct
+{
+  const jerry_char_t *ptr; /**< pointer to the string */
+  jerry_size_t size; /**< size of thestring */
+} jerry_string_t;
+
 /**
  * Option bits for jerry_parse_options_t.
  */
@@ -246,6 +255,7 @@ typedef enum
  */
 typedef enum
 {
+  JERRY_ENCODING_ASCII, /**< ascii encoding */
   JERRY_ENCODING_CESU8, /**< cesu-8 encoding */
   JERRY_ENCODING_UTF8, /**< utf-8 encoding */
 } jerry_encoding_t;
@@ -856,10 +866,16 @@ typedef void (*jerry_arraybuffer_free_cb_t) (jerry_arraybuffer_type_t buffer_typ
                                              void *arraybuffer_user_p,
                                              void *user_p);
 
+/**
+ * Helper to to ensure str is a string literal
+ */
+#define JERRY_ZSTR_ENSURE_STRING_LITERAL(str) str ""
+
 /**
  * Helper to expand string literal to [string pointer, string size] argument pair.
  */
-#define JERRY_ZSTR_ARG(str) ((const jerry_char_t *) (str)), ((jerry_size_t) (sizeof (str) - 1))
+#define JERRY_ZSTR_ARG(str) \
+  ((const jerry_char_t *) (JERRY_ZSTR_ENSURE_STRING_LITERAL (str))), ((jerry_size_t) (sizeof (str) - 1))
 
 /**
  * @}
diff --git a/jerry-core/jrt/jrt.h b/jerry-core/jrt/jrt.h
index 2c1f308d96..9c18653f81 100644
--- a/jerry-core/jrt/jrt.h
+++ b/jerry-core/jrt/jrt.h
@@ -30,11 +30,6 @@
  */
 #define JERRY_BITSINBYTE 8
 
-/*
- * Make sure unused parameters, variables, or expressions trigger no compiler warning.
- */
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define JERRY_UNUSED_1(_1)                             JERRY_UNUSED (_1)
 #define JERRY_UNUSED_2(_1, _2)                         JERRY_UNUSED (_1), JERRY_UNUSED_1 (_2)
 #define JERRY_UNUSED_3(_1, _2, _3)                     JERRY_UNUSED (_1), JERRY_UNUSED_2 (_2, _3)
diff --git a/jerry-core/lit/lit-strings.c b/jerry-core/lit/lit-strings.c
index edc75f8a2a..b25a98fe39 100644
--- a/jerry-core/lit/lit-strings.c
+++ b/jerry-core/lit/lit-strings.c
@@ -26,6 +26,35 @@
 #define LIT_UTF8_2_BYTE_MAX           0x8f /**< utf8 two byte max */
 #define LIT_UTF8_VALID_TWO_BYTE_START 0xc2 /**< utf8 two byte start */
 
+/**
+ * Validate ascii string
+ *
+ *
+ * @return true if ascii string is well-formed
+ *         false otherwise
+ */
+bool
+lit_is_valid_ascii_string (const lit_utf8_byte_t *ascii_buf_p, /**< ascii string */
+                           lit_utf8_size_t buf_size) /**< string size */
+{
+  const unsigned char *end = buf_size + ascii_buf_p;
+
+  const unsigned char *idx = (const unsigned char *) ascii_buf_p;
+
+  while (idx < end)
+  {
+    const uint8_t first_byte = *idx++;
+
+    if (first_byte < LIT_UTF8_EXTRA_BYTE_MARKER)
+    {
+      continue;
+    }
+    return false;
+  }
+
+  return true;
+} /* lit_is_valid_ascii_string */
+
 /**
  * Validate utf-8 string
  *
@@ -251,22 +280,6 @@ lit_utf16_encode_code_point (lit_code_point_t cp, /**< the code point we encode
   return 2;
 } /* lit_utf16_encode_code_point */
 
-/**
- * Calculate size of a zero-terminated utf-8 string
- *
- * NOTE:
- *   - string cannot be NULL
- *   - string should not contain zero characters in the middle
- *
- * @return size of a string
- */
-lit_utf8_size_t
-lit_zt_utf8_string_size (const lit_utf8_byte_t *utf8_str_p) /**< zero-terminated utf-8 string */
-{
-  JERRY_ASSERT (utf8_str_p != NULL);
-  return (lit_utf8_size_t) strlen ((const char *) utf8_str_p);
-} /* lit_zt_utf8_string_size */
-
 /**
  * Calculate length of a cesu-8 encoded string
  *
diff --git a/jerry-core/lit/lit-strings.h b/jerry-core/lit/lit-strings.h
index d00480e641..f868d130b5 100644
--- a/jerry-core/lit/lit-strings.h
+++ b/jerry-core/lit/lit-strings.h
@@ -84,6 +84,7 @@
 #define LIT_UTF8_FIRST_BYTE_MAX (0xF8)
 
 /* validation */
+bool lit_is_valid_ascii_string (const lit_utf8_byte_t *ascii_buf_p, lit_utf8_size_t buf_size);
 bool lit_is_valid_utf8_string (const lit_utf8_byte_t *utf8_buf_p, lit_utf8_size_t buf_size, bool strict);
 bool lit_is_valid_cesu8_string (const lit_utf8_byte_t *cesu8_buf_p, lit_utf8_size_t buf_size);
 
@@ -92,7 +93,6 @@ bool lit_is_code_point_utf16_low_surrogate (lit_code_point_t code_point);
 bool lit_is_code_point_utf16_high_surrogate (lit_code_point_t code_point);
 
 /* size */
-lit_utf8_size_t lit_zt_utf8_string_size (const lit_utf8_byte_t *utf8_str_p);
 lit_utf8_size_t lit_get_utf8_size_of_cesu8_string (const lit_utf8_byte_t *cesu8_buf_p, lit_utf8_size_t cesu8_buf_size);
 
 /* length */
diff --git a/jerry-ext/arg/arg-transform-functions.c b/jerry-ext/arg/arg-transform-functions.c
index 264c2d29dc..ff6e8e0e62 100644
--- a/jerry-ext/arg/arg-transform-functions.c
+++ b/jerry-ext/arg/arg-transform-functions.c
@@ -56,7 +56,7 @@ jerryx_arg_transform_number_strict_common (jerryx_arg_js_iterator_t *js_arg_iter
 
   if (!jerry_value_is_number (js_arg))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It is not a number.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It is not a number."));
   }
 
   *number_p = jerry_value_as_number (js_arg);
@@ -83,7 +83,7 @@ jerryx_arg_transform_number_common (jerryx_arg_js_iterator_t *js_arg_iter_p, /**
   {
     jerry_value_free (to_number);
 
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It can not be converted to a number.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It can not be converted to a number."));
   }
 
   *number_p = jerry_value_as_number (to_number);
@@ -133,14 +133,14 @@ jerryx_arg_helper_process_double (double *d, /**< [in, out] the number to be pro
 {
   if (*d != *d) /* isnan (*d) triggers conversion warning on clang<9 */
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "The number is NaN.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("The number is NaN."));
   }
 
   if (option.clamp == JERRYX_ARG_NO_CLAMP)
   {
     if (*d > max || *d < min)
     {
-      return jerry_throw_sz (JERRY_ERROR_TYPE, "The number is out of range.");
+      return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("The number is out of range."));
     }
   }
   else
@@ -220,7 +220,7 @@ jerryx_arg_transform_boolean_strict (jerryx_arg_js_iterator_t *js_arg_iter_p, /*
 
   if (!jerry_value_is_boolean (js_arg))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It is not a boolean.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It is not a boolean."));
   }
 
   bool *dest = c_arg_p->dest;
@@ -268,7 +268,7 @@ jerryx_arg_string_to_buffer_common_routine (jerry_value_t js_arg, /**< JS arg */
 
   if (size > target_buf_size - 1)
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Buffer size is not large enough.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Buffer size is not large enough."));
   }
 
   jerry_string_to_buffer (js_arg, encoding, target_p, target_buf_size);
@@ -292,7 +292,7 @@ jerryx_arg_transform_string_strict_common (jerryx_arg_js_iterator_t *js_arg_iter
 
   if (!jerry_value_is_string (js_arg))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It is not a string.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It is not a string."));
   }
 
   return jerryx_arg_string_to_buffer_common_routine (js_arg, c_arg_p, encoding);
@@ -317,7 +317,7 @@ jerryx_arg_transform_string_common (jerryx_arg_js_iterator_t *js_arg_iter_p, /**
   {
     jerry_value_free (to_string);
 
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It can not be converted to a string.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It can not be converted to a string."));
   }
 
   jerry_value_t ret = jerryx_arg_string_to_buffer_common_routine (to_string, c_arg_p, encoding);
@@ -404,7 +404,7 @@ jerryx_arg_transform_function (jerryx_arg_js_iterator_t *js_arg_iter_p, /**< ava
 
   if (!jerry_value_is_function (js_arg))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It is not a function.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It is not a function."));
   }
 
   jerry_value_t *func_p = c_arg_p->dest;
@@ -428,7 +428,7 @@ jerryx_arg_transform_native_pointer (jerryx_arg_js_iterator_t *js_arg_iter_p, /*
 
   if (!jerry_value_is_object (js_arg))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It is not an object.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It is not an object."));
   }
 
   const jerry_object_native_info_t *expected_info_p;
@@ -438,7 +438,8 @@ jerryx_arg_transform_native_pointer (jerryx_arg_js_iterator_t *js_arg_iter_p, /*
 
   if (*ptr_p == NULL)
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "The object has no native pointer or type does not match.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE,
+                           jerry_sz_ascii ("The object has no native pointer or type does not match."));
   }
 
   return jerry_undefined ();
diff --git a/jerry-ext/arg/arg.c b/jerry-ext/arg/arg.c
index 87638b1d3a..61d09f2819 100644
--- a/jerry-ext/arg/arg.c
+++ b/jerry-ext/arg/arg.c
@@ -77,7 +77,7 @@ jerryx_arg_transform_this_and_args (const jerry_value_t this_val, /**< the this_
   {
     jerry_value_free (ret);
 
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "'this' validation failed.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("'this' validation failed."));
   }
 
   return jerryx_arg_transform_args (js_arg_p, js_arg_cnt, c_arg_p + 1, c_arg_cnt - 1);
@@ -92,23 +92,21 @@ jerryx_arg_transform_this_and_args (const jerry_value_t this_val, /**< the this_
  */
 jerry_value_t
 jerryx_arg_transform_object_properties (const jerry_value_t obj_val, /**< the JS object */
-                                        const jerry_char_t **name_p, /**< property name list of the JS object */
+                                        const jerry_value_t *name_p, /**< property name list of the JS object */
                                         const jerry_length_t name_cnt, /**< count of the name list */
                                         const jerryx_arg_t *c_arg_p, /**< points to the array of transformation steps */
                                         jerry_length_t c_arg_cnt) /**< the count of the `c_arg_p` array */
 {
   if (!jerry_value_is_object (obj_val))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Not an object.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Not an object."));
   }
 
   JERRY_VLA (jerry_value_t, prop, name_cnt);
 
-  for (jerry_length_t i = 0; i < name_cnt; i++, name_p++)
+  for (jerry_length_t i = 0; i < name_cnt; i++)
   {
-    const jerry_value_t name_str = jerry_string_sz ((char *) (*name_p));
-    prop[i] = jerry_object_get (obj_val, name_str);
-    jerry_value_free (name_str);
+    prop[i] = jerry_object_get (obj_val, name_p[i]);
 
     if (jerry_value_is_exception (prop[i]))
     {
@@ -144,7 +142,7 @@ jerryx_arg_transform_array (const jerry_value_t array_val, /**< points to the JS
 {
   if (!jerry_value_is_array (array_val))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Not an array.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Not an array."));
   }
 
   JERRY_VLA (jerry_value_t, arr, c_arg_cnt);
diff --git a/jerry-ext/common/jext-common.h b/jerry-ext/common/jext-common.h
index 946de890ba..afba6f35f9 100644
--- a/jerry-ext/common/jext-common.h
+++ b/jerry-ext/common/jext-common.h
@@ -22,11 +22,6 @@
 #include "jerryscript-port.h"
 #include "jerryscript.h"
 
-/*
- * Make sure unused parameters, variables, or expressions trigger no compiler warning.
- */
-#define JERRYX_UNUSED(x) ((void) (x))
-
 /*
  * Asserts
  *
@@ -70,7 +65,7 @@ void JERRY_ATTR_NORETURN jerry_unreachable (const char *file, const char *functi
   {                      \
     if (false)           \
     {                    \
-      JERRYX_UNUSED (x); \
+      JERRY_UNUSED (x);  \
     }                    \
   } while (0)
 
diff --git a/jerry-ext/debugger/debugger-common.c b/jerry-ext/debugger/debugger-common.c
index 9b03f2239b..3f2915df95 100644
--- a/jerry-ext/debugger/debugger-common.c
+++ b/jerry-ext/debugger/debugger-common.c
@@ -35,7 +35,7 @@ jerryx_debugger_after_connect (bool success) /**< tells whether the connection
     jerry_debugger_transport_close ();
   }
 #else /* !(defined (JERRY_DEBUGGER) && (JERRY_DEBUGGER == 1)) */
-  JERRYX_UNUSED (success);
+  JERRY_UNUSED (success);
 #endif /* defined (JERRY_DEBUGGER) && (JERRY_DEBUGGER == 1) */
 } /* jerryx_debugger_after_connect */
 
diff --git a/jerry-ext/debugger/debugger-serial.c b/jerry-ext/debugger/debugger-serial.c
index 3a4215f087..8a0c5ff204 100644
--- a/jerry-ext/debugger/debugger-serial.c
+++ b/jerry-ext/debugger/debugger-serial.c
@@ -402,7 +402,7 @@ jerryx_debugger_serial_create (const char *config) /**< specify the configuratio
 bool
 jerryx_debugger_serial_create (const char *config)
 {
-  JERRYX_UNUSED (config);
+  JERRY_UNUSED (config);
   return false;
 } /* jerryx_debugger_serial_create */
 
diff --git a/jerry-ext/debugger/debugger-tcp.c b/jerry-ext/debugger/debugger-tcp.c
index 8483470559..76cbc9a12d 100644
--- a/jerry-ext/debugger/debugger-tcp.c
+++ b/jerry-ext/debugger/debugger-tcp.c
@@ -399,7 +399,7 @@ jerryx_debugger_tcp_create (uint16_t port) /**< listening port */
 bool
 jerryx_debugger_tcp_create (uint16_t port)
 {
-  JERRYX_UNUSED (port);
+  JERRY_UNUSED (port);
   return false;
 } /* jerryx_debugger_tcp_create */
 
diff --git a/jerry-ext/include/jerryscript-ext/arg.h b/jerry-ext/include/jerryscript-ext/arg.h
index aa70878f6f..e397815c51 100644
--- a/jerry-ext/include/jerryscript-ext/arg.h
+++ b/jerry-ext/include/jerryscript-ext/arg.h
@@ -45,7 +45,7 @@ typedef jerry_value_t (*jerryx_arg_transform_func_t) (jerryx_arg_js_iterator_t *
  */
 typedef struct
 {
-  const jerry_char_t **name_p; /**< property name list of the JS object */
+  const jerry_value_t *name_p; /**< property name list of the JS object */
   jerry_length_t name_cnt; /**< count of the name list */
   const jerryx_arg_t *c_arg_p; /**< points to the array of transformation steps */
   jerry_length_t c_arg_cnt; /**< the count of the `c_arg_p` array */
@@ -82,7 +82,7 @@ jerry_value_t jerryx_arg_transform_args (const jerry_value_t *js_arg_p,
                                          jerry_length_t c_arg_cnt);
 
 jerry_value_t jerryx_arg_transform_object_properties (const jerry_value_t obj_val,
-                                                      const jerry_char_t **name_p,
+                                                      const jerry_value_t *name_p,
                                                       const jerry_length_t name_cnt,
                                                       const jerryx_arg_t *c_arg_p,
                                                       jerry_length_t c_arg_cnt);
diff --git a/jerry-ext/include/jerryscript-ext/module.h b/jerry-ext/include/jerryscript-ext/module.h
index 32166abcf7..1ed72b4952 100644
--- a/jerry-ext/include/jerryscript-ext/module.h
+++ b/jerry-ext/include/jerryscript-ext/module.h
@@ -31,7 +31,7 @@ typedef jerry_value_t (*jerryx_native_module_on_resolve_t) (void);
  */
 typedef struct jerryx_native_module_t
 {
-  const jerry_char_t *name_p; /**< name of the module */
+  jerry_string_t name; /**< name of the module */
   const jerryx_native_module_on_resolve_t on_resolve_p; /**< function that returns a new instance of the module */
   struct jerryx_native_module_t *next_p; /**< pointer to next module in the list */
 } jerryx_native_module_t;
@@ -99,19 +99,19 @@ typedef struct jerryx_native_module_t
  */
 #define JERRYX_NATIVE_MODULE(module_name, on_resolve_cb) JERRYX_NATIVE_MODULE_IMPLEM (module_name, on_resolve_cb)
 
-#define JERRYX_NATIVE_MODULE_IMPLEM(module_name, on_resolve_cb)                                          \
-  static jerryx_native_module_t _##module_name##_definition = { .name_p = (jerry_char_t *) #module_name, \
-                                                                .on_resolve_p = (on_resolve_cb),         \
-                                                                .next_p = NULL };                        \
-                                                                                                         \
-  JERRYX_MODULE_CONSTRUCTOR (module_name##_register)                                                     \
-  {                                                                                                      \
-    jerryx_native_module_register (&_##module_name##_definition);                                        \
-  }                                                                                                      \
-                                                                                                         \
-  JERRYX_MODULE_DESTRUCTOR (module_name##_unregister)                                                    \
-  {                                                                                                      \
-    jerryx_native_module_unregister (&_##module_name##_definition);                                      \
+#define JERRYX_NATIVE_MODULE_IMPLEM(module_name, on_resolve_cb)                                            \
+  static jerryx_native_module_t _##module_name##_definition = { .name = { JERRY_ZSTR_ARG (#module_name) }, \
+                                                                .on_resolve_p = (on_resolve_cb),           \
+                                                                .next_p = NULL };                          \
+                                                                                                           \
+  JERRYX_MODULE_CONSTRUCTOR (module_name##_register)                                                       \
+  {                                                                                                        \
+    jerryx_native_module_register (&_##module_name##_definition);                                          \
+  }                                                                                                        \
+                                                                                                           \
+  JERRYX_MODULE_DESTRUCTOR (module_name##_unregister)                                                      \
+  {                                                                                                        \
+    jerryx_native_module_unregister (&_##module_name##_definition);                                        \
   }
 
 /**
diff --git a/jerry-ext/include/jerryscript-ext/properties.h b/jerry-ext/include/jerryscript-ext/properties.h
index 3ad644680d..cbd818daed 100644
--- a/jerry-ext/include/jerryscript-ext/properties.h
+++ b/jerry-ext/include/jerryscript-ext/properties.h
@@ -16,7 +16,7 @@
 #ifndef JERRYX_PROPERTIES_H
 #define JERRYX_PROPERTIES_H
 
-#include "jerryscript-types.h"
+#include "jerryscript-core.h"
 
 JERRY_C_API_BEGIN
 
@@ -24,7 +24,7 @@ JERRY_C_API_BEGIN
  * Handler registration helper
  */
 
-bool jerryx_register_global (const char *name_p, jerry_external_handler_t handler_p);
+bool jerryx_register_global (jerry_value_t function_name_val, jerry_external_handler_t handler_p);
 
 /**
  * Struct used by the `jerryx_set_functions` method to
@@ -32,44 +32,44 @@ bool jerryx_register_global (const char *name_p, jerry_external_handler_t handle
  */
 typedef struct
 {
-  const char *name; /**< name of the property to add */
+  jerry_value_t name; /**< name of the property to add */
   jerry_value_t value; /**< value of the property */
 } jerryx_property_entry;
 
-#define JERRYX_PROPERTY_NUMBER(NAME, NUMBER) \
-  (jerryx_property_entry)                    \
-  {                                          \
-    NAME, jerry_number (NUMBER)              \
+#define JERRYX_PROPERTY_NUMBER(NAME, NUMBER)     \
+  (jerryx_property_entry)                        \
+  {                                              \
+    jerry_sz_ascii (NAME), jerry_number (NUMBER) \
   }
-#define JERRYX_PROPERTY_STRING(NAME, STR, SIZE)                                \
-  (jerryx_property_entry)                                                      \
-  {                                                                            \
-    NAME, jerry_string ((const jerry_char_t *) STR, SIZE, JERRY_ENCODING_UTF8) \
+#define JERRYX_PROPERTY_STRING(NAME, STR, SIZE)                                 \
+  (jerryx_property_entry)                                                       \
+  {                                                                             \
+    jerry_sz_ascii (NAME), jerry_string_utf8 ((const jerry_char_t *) STR, SIZE) \
   }
-#define JERRYX_PROPERTY_STRING_SZ(NAME, STR) \
-  (jerryx_property_entry)                    \
-  {                                          \
-    NAME, jerry_string_sz (STR)              \
+#define JERRYX_PROPERTY_STRING_SZ(NAME, STR)    \
+  (jerryx_property_entry)                       \
+  {                                             \
+    jerry_sz_ascii (NAME), jerry_sz_ascii (STR) \
   }
-#define JERRYX_PROPERTY_BOOLEAN(NAME, VALUE) \
-  (jerryx_property_entry)                    \
-  {                                          \
-    NAME, jerry_boolean (VALUE)              \
+#define JERRYX_PROPERTY_BOOLEAN(NAME, VALUE)     \
+  (jerryx_property_entry)                        \
+  {                                              \
+    jerry_sz_ascii (NAME), jerry_boolean (VALUE) \
   }
-#define JERRYX_PROPERTY_FUNCTION(NAME, FUNC) \
-  (jerryx_property_entry)                    \
-  {                                          \
-    NAME, jerry_function_external (FUNC)     \
+#define JERRYX_PROPERTY_FUNCTION(NAME, FUNC)              \
+  (jerryx_property_entry)                                 \
+  {                                                       \
+    jerry_sz_ascii (NAME), jerry_function_external (FUNC) \
   }
-#define JERRYX_PROPERTY_UNDEFINED(NAME) \
-  (jerryx_property_entry)               \
-  {                                     \
-    NAME, jerry_undefined ()            \
+#define JERRYX_PROPERTY_UNDEFINED(NAME)       \
+  (jerryx_property_entry)                     \
+  {                                           \
+    jerry_sz_ascii (NAME), jerry_undefined () \
   }
-#define JERRYX_PROPERTY_LIST_END() \
-  (jerryx_property_entry)          \
-  {                                \
-    NULL, 0                        \
+#define JERRYX_PROPERTY_LIST_END()         \
+  (jerryx_property_entry)                  \
+  {                                        \
+    jerry_undefined (), jerry_undefined () \
   }
 
 /**
diff --git a/jerry-ext/module/module.c b/jerry-ext/module/module.c
index 01f7d151e6..7404642b84 100644
--- a/jerry-ext/module/module.c
+++ b/jerry-ext/module/module.c
@@ -19,9 +19,9 @@
 
 #include "jerryscript.h"
 
-static const char *module_name_property_name = "moduleName";
-static const char *module_not_found = "Module not found";
-static const char *module_name_not_string = "Module name is not a string";
+#define module_name_property_name "moduleName"
+#define module_not_found          "Module not found"
+#define module_name_not_string    "Module name is not a string"
 
 /**
  * Create an error related to modules
@@ -33,11 +33,11 @@ static const char *module_name_not_string = "Module name is not a string";
  */
 static jerry_value_t
 jerryx_module_create_error (jerry_error_t error_type, /**< the type of error to create */
-                            const char *message, /**< the error message */
+                            jerry_value_t message, /**< the error message */
                             const jerry_value_t module_name) /**< the module name */
 {
   jerry_value_t error_object = jerry_error_sz (error_type, message);
-  jerry_value_t property_name = jerry_string_sz (module_name_property_name);
+  jerry_value_t property_name = jerry_sz_ascii (module_name_property_name);
 
   jerry_value_free (jerry_object_set (error_object, property_name, module_name));
 
@@ -164,7 +164,7 @@ jerryx_module_add_to_cache (jerry_value_t cache, /**< cache to which to add the
   return ret;
 } /* jerryx_module_add_to_cache */
 
-static const char *on_resolve_absent = "Module on_resolve () must not be NULL";
+#define on_resolve_absent "Module on_resolve () must not be NULL"
 
 /**
  * Declare and define the default module resolver - one which examines what modules are defined in the above linker
@@ -184,13 +184,13 @@ jerryx_resolve_native_module (const jerry_value_t canonical_name, /**< canonical
   /* Look for the module by its name in the list of module definitions. */
   for (module_p = first_module_p; module_p != NULL; module_p = module_p->next_p)
   {
-    if (module_p->name_p != NULL && strlen ((char *) module_p->name_p) == name_size
-        && !strncmp ((char *) module_p->name_p, (char *) name_string, name_size))
+    if (module_p->name.size == name_size && !strncmp ((char *) module_p->name.ptr, (char *) name_string, name_size))
     {
       /* If we find the module by its name we load it and cache it if it has an on_resolve () and complain otherwise. */
       (*result) =
-        ((module_p->on_resolve_p) ? module_p->on_resolve_p ()
-                                  : jerryx_module_create_error (JERRY_ERROR_TYPE, on_resolve_absent, canonical_name));
+        ((module_p->on_resolve_p)
+           ? module_p->on_resolve_p ()
+           : jerryx_module_create_error (JERRY_ERROR_TYPE, jerry_sz_ascii (on_resolve_absent), canonical_name));
       return true;
     }
   }
@@ -218,7 +218,7 @@ jerryx_module_resolve_local (const jerry_value_t name, /**< name of the module t
   {
     if (result != NULL)
     {
-      *result = jerryx_module_create_error (JERRY_ERROR_COMMON, module_name_not_string, name);
+      *result = jerryx_module_create_error (JERRY_ERROR_COMMON, jerry_sz_ascii (module_name_not_string), name);
     }
     goto done;
   }
@@ -268,7 +268,7 @@ jerryx_module_resolve_local (const jerry_value_t name, /**< name of the module t
   }
 
   /* If none of the resolvers manage to find the module, complain with "Module not found" */
-  *result = jerryx_module_create_error (JERRY_ERROR_COMMON, module_not_found, name);
+  *result = jerryx_module_create_error (JERRY_ERROR_COMMON, jerry_sz_ascii (module_not_found), name);
 
 done:
   /* Release the canonical names as returned by the various resolvers. */
diff --git a/jerry-ext/util/handlers.c b/jerry-ext/util/handlers.c
index 10d2a1ed0b..24d24b4f71 100644
--- a/jerry-ext/util/handlers.c
+++ b/jerry-ext/util/handlers.c
@@ -193,7 +193,7 @@ jerryx_handler_source_received (const jerry_char_t *source_name_p, /**< resource
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string (source_name_p, (jerry_size_t) source_name_size, JERRY_ENCODING_UTF8);
+  parse_options.source_name = jerry_string_utf8 (source_name_p, (jerry_size_t) source_name_size);
 
   jerry_value_t ret_val = jerry_parse (source_p, source_size, &parse_options);
 
diff --git a/jerry-ext/util/print.c b/jerry-ext/util/print.c
index 6e79a8eb75..a51d4cc48a 100644
--- a/jerry-ext/util/print.c
+++ b/jerry-ext/util/print.c
@@ -282,7 +282,7 @@ jerryx_print_unhandled_exception (jerry_value_t exception) /**< exception value
 
   if (jerry_value_is_object (value))
   {
-    jerry_value_t backtrace_val = jerry_object_get_sz (value, "stack");
+    jerry_value_t backtrace_val = jerry_object_get_sz (value, jerry_sz_ascii ("stack"));
 
     if (jerry_value_is_array (backtrace_val))
     {
diff --git a/jerry-ext/util/properties.c b/jerry-ext/util/properties.c
index 58b4085db3..a327a7a53f 100644
--- a/jerry-ext/util/properties.c
+++ b/jerry-ext/util/properties.c
@@ -24,11 +24,10 @@
  *         false - otherwise.
  */
 bool
-jerryx_register_global (const char *name_p, /**< name of the function */
+jerryx_register_global (jerry_value_t function_name_val, /**< name of the function that will be free/take */
                         jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
-  jerry_value_t function_name_val = jerry_string_sz (name_p);
   jerry_value_t function_val = jerry_function_external (handler_p);
 
   jerry_value_t result_val = jerry_object_set (global_obj_val, function_name_val, function_val);
@@ -70,14 +69,11 @@ jerryx_set_properties (const jerry_value_t target_object, /**< target object */
     return JERRYX_SET_PROPERTIES_RESULT (jerry_undefined (), 0);
   }
 
-  for (; (entries[idx].name != NULL); idx++)
+  for (; !jerry_value_is_undefined (entries[idx].name); idx++)
   {
     const jerryx_property_entry *entry = &entries[idx];
 
-    jerry_value_t prop_name = jerry_string_sz (entry->name);
-    jerry_value_t result = jerry_object_set (target_object, prop_name, entry->value);
-
-    jerry_value_free (prop_name);
+    jerry_value_t result = jerry_object_set (target_object, entry->name, entry->value);
 
     // By API definition:
     // The jerry_object_set returns TRUE if there is no problem
@@ -88,6 +84,7 @@ jerryx_set_properties (const jerry_value_t target_object, /**< target object */
       return JERRYX_SET_PROPERTIES_RESULT (result, idx);
     }
 
+    jerry_value_free (entry->name);
     jerry_value_free (entry->value);
     jerry_value_free (result);
   }
@@ -111,8 +108,9 @@ jerryx_release_property_entry (const jerryx_property_entry entries[], /**< list
     return;
   }
 
-  for (uint32_t idx = register_result.registered; entries[idx].name != NULL; idx++)
+  for (uint32_t idx = register_result.registered; !jerry_value_is_undefined (entries[idx].name); idx++)
   {
+    jerry_value_free (entries[idx].name);
     jerry_value_free (entries[idx].value);
   }
 } /* jerryx_release_property_entry */
diff --git a/jerry-ext/util/repl.c b/jerry-ext/util/repl.c
index ad58ffc1f9..700b901ddf 100644
--- a/jerry-ext/util/repl.c
+++ b/jerry-ext/util/repl.c
@@ -50,7 +50,7 @@ jerryx_repl (const jerry_char_t *prompt_p, jerry_size_t prompt_size)
     if (!jerry_validate_string (line_p, length, JERRY_ENCODING_UTF8))
     {
       jerry_port_line_free (line_p);
-      result = jerry_throw_sz (JERRY_ERROR_SYNTAX, "Input is not a valid UTF-8 string");
+      result = jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Input is not a valid UTF-8 string"));
       goto exception;
     }
 
diff --git a/jerry-ext/util/sources.c b/jerry-ext/util/sources.c
index dbd629ee7a..0620cd2f23 100644
--- a/jerry-ext/util/sources.c
+++ b/jerry-ext/util/sources.c
@@ -35,19 +35,18 @@ jerryx_source_parse_script (const char *path_p)
   if (source_p == NULL)
   {
     jerry_log (JERRY_LOG_LEVEL_ERROR, "Failed to open file: %s\n", path_p);
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Source file not found");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Source file not found"));
   }
 
   if (!jerry_validate_string (source_p, source_size, JERRY_ENCODING_UTF8))
   {
     jerry_port_source_free (source_p);
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Input is not a valid UTF-8 encoded string.");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Input is not a valid UTF-8 encoded string."));
   }
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name =
-    jerry_string ((const jerry_char_t *) path_p, (jerry_size_t) strlen (path_p), JERRY_ENCODING_UTF8);
+  parse_options.source_name = jerry_string_utf8 ((const jerry_char_t *) path_p, (jerry_size_t) strlen (path_p));
 
   jerry_value_t result = jerry_parse (source_p, source_size, &parse_options);
 
@@ -75,8 +74,7 @@ jerryx_source_exec_script (const char *path_p)
 jerry_value_t
 jerryx_source_exec_module (const char *path_p)
 {
-  jerry_value_t specifier =
-    jerry_string ((const jerry_char_t *) path_p, (jerry_size_t) strlen (path_p), JERRY_ENCODING_UTF8);
+  jerry_value_t specifier = jerry_string_utf8 ((const jerry_char_t *) path_p, (jerry_size_t) strlen (path_p));
   jerry_value_t referrer = jerry_undefined ();
 
   jerry_value_t module = jerry_module_resolve (specifier, referrer, NULL);
@@ -118,7 +116,7 @@ jerryx_source_exec_snapshot (const char *path_p, size_t function_index)
   if (source_p == NULL)
   {
     jerry_log (JERRY_LOG_LEVEL_ERROR, "Failed to open file: %s\n", path_p);
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Snapshot file not found");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Snapshot file not found"));
   }
 
   jerry_value_t result =
@@ -148,7 +146,7 @@ jerryx_source_exec_stdin (void)
     source_p = realloc (source_p, new_size);
     if (source_p == NULL)
     {
-      return jerry_throw_sz (JERRY_ERROR_COMMON, "Out of memory.");
+      return jerry_throw_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Out of memory."));
     }
 
     memcpy (source_p + source_size, line_p, line_size);
@@ -159,7 +157,7 @@ jerryx_source_exec_stdin (void)
   if (!jerry_validate_string (source_p, source_size, JERRY_ENCODING_UTF8))
   {
     free (source_p);
-    return jerry_throw_sz (JERRY_ERROR_SYNTAX, "Input is not a valid UTF-8 encoded string.");
+    return jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("Input is not a valid UTF-8 encoded string."));
   }
 
   jerry_value_t result = jerry_parse (source_p, source_size, NULL);
diff --git a/jerry-ext/util/test262.c b/jerry-ext/util/test262.c
index 278075d1d4..582f41c5d1 100644
--- a/jerry-ext/util/test262.c
+++ b/jerry-ext/util/test262.c
@@ -27,11 +27,11 @@
  */
 static void
 jerryx_test262_register_function (jerry_value_t test262_obj, /** $262 object */
-                                  const char *name_p, /**< name of the function */
+                                  jerry_value_t name_sz, /**< name of the function that will be free/take*/
                                   jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t function_val = jerry_function_external (handler_p);
-  jerry_value_t result_val = jerry_object_set_sz (test262_obj, name_p, function_val);
+  jerry_value_t result_val = jerry_object_set_sz (test262_obj, name_sz, function_val);
   jerry_value_free (function_val);
 
   assert (!jerry_value_is_exception (result_val));
@@ -55,7 +55,7 @@ jerryx_test262_detach_array_buffer (const jerry_call_info_t *call_info_p, /**< c
 
   if (args_cnt < 1 || !jerry_value_is_arraybuffer (args_p[0]))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Expected an ArrayBuffer object");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Expected an ArrayBuffer object"));
   }
 
   /* TODO: support the optional 'key' argument */
@@ -79,7 +79,7 @@ jerryx_test262_eval_script (const jerry_call_info_t *call_info_p, /**< call info
 
   if (args_cnt < 1 || !jerry_value_is_string (args_p[0]))
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Expected a string");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Expected a string"));
   }
 
   jerry_value_t ret_value = jerry_parse_value (args_p[0], NULL);
@@ -133,12 +133,14 @@ jerryx_test262_create (jerry_value_t global_obj) /**< global object */
 {
   jerry_value_t test262_object = jerry_object ();
 
-  jerryx_test262_register_function (test262_object, "detachArrayBuffer", jerryx_test262_detach_array_buffer);
-  jerryx_test262_register_function (test262_object, "evalScript", jerryx_test262_eval_script);
-  jerryx_test262_register_function (test262_object, "createRealm", jerryx_test262_create_realm);
-  jerryx_test262_register_function (test262_object, "gc", jerryx_handler_gc);
+  jerryx_test262_register_function (test262_object,
+                                    jerry_sz_ascii ("detachArrayBuffer"),
+                                    jerryx_test262_detach_array_buffer);
+  jerryx_test262_register_function (test262_object, jerry_sz_ascii ("evalScript"), jerryx_test262_eval_script);
+  jerryx_test262_register_function (test262_object, jerry_sz_ascii ("createRealm"), jerryx_test262_create_realm);
+  jerryx_test262_register_function (test262_object, jerry_sz_ascii ("gc"), jerryx_handler_gc);
 
-  jerry_value_t result = jerry_object_set_sz (test262_object, "global", global_obj);
+  jerry_value_t result = jerry_object_set_sz (test262_object, jerry_sz_ascii ("global"), global_obj);
   assert (!jerry_value_is_exception (result));
   jerry_value_free (result);
 
@@ -154,7 +156,7 @@ jerryx_test262_register (void)
   jerry_value_t global_obj = jerry_current_realm ();
   jerry_value_t test262_obj = jerryx_test262_create (global_obj);
 
-  jerry_value_t result = jerry_object_set_sz (global_obj, "$262", test262_obj);
+  jerry_value_t result = jerry_object_set_sz (global_obj, jerry_sz_ascii ("$262"), test262_obj);
   assert (!jerry_value_is_exception (result));
 
   jerry_value_free (result);
diff --git a/jerry-main/benchmark/main-benchmark.c b/jerry-main/benchmark/main-benchmark.c
index 25cf741b62..0c94329bd3 100644
--- a/jerry-main/benchmark/main-benchmark.c
+++ b/jerry-main/benchmark/main-benchmark.c
@@ -87,7 +87,7 @@ run (void)
 
     if (source_p == NULL)
     {
-      ret_value = jerry_throw_sz (JERRY_ERROR_COMMON, "");
+      ret_value = jerry_throw_sz (JERRY_ERROR_COMMON, jerry_sz_ascii (""));
       break;
     }
     else
diff --git a/jerry-main/main-desktop.c b/jerry-main/main-desktop.c
index 920ea9ca6f..ade2a43732 100644
--- a/jerry-main/main-desktop.c
+++ b/jerry-main/main-desktop.c
@@ -100,11 +100,11 @@ main_init_engine (main_args_t *arguments_p) /**< main arguments */
     jerryx_test262_register ();
   }
 
-  jerryx_register_global ("assert", jerryx_handler_assert);
-  jerryx_register_global ("gc", jerryx_handler_gc);
-  jerryx_register_global ("print", jerryx_handler_print);
-  jerryx_register_global ("sourceName", jerryx_handler_source_name);
-  jerryx_register_global ("createRealm", jerryx_handler_create_realm);
+  jerryx_register_global (jerry_sz_ascii ("assert"), jerryx_handler_assert);
+  jerryx_register_global (jerry_sz_ascii ("gc"), jerryx_handler_gc);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("sourceName"), jerryx_handler_source_name);
+  jerryx_register_global (jerry_sz_ascii ("createRealm"), jerryx_handler_create_realm);
 } /* main_init_engine */
 
 int
@@ -245,7 +245,10 @@ main (int argc, char **argv)
   if (arguments.exit_cb_name_p != NULL)
   {
     jerry_value_t global = jerry_current_realm ();
-    jerry_value_t callback_fn = jerry_object_get_sz (global, arguments.exit_cb_name_p);
+    jerry_value_t callback_fn =
+      jerry_object_get_sz (global,
+                           jerry_string_utf8 ((const jerry_char_t *) arguments.exit_cb_name_p,
+                                              (jerry_size_t) strlen (arguments.exit_cb_name_p)));
     jerry_value_free (global);
 
     if (jerry_value_is_function (callback_fn))
diff --git a/jerry-main/main-snapshot.c b/jerry-main/main-snapshot.c
index f6c913fe48..915ae98d48 100644
--- a/jerry-main/main-snapshot.c
+++ b/jerry-main/main-snapshot.c
@@ -339,14 +339,13 @@ process_generate (cli_state_t *cli_state_p, /**< cli state */
   /* To avoid cppcheck warning. */
   parse_options.argument_list = 0;
   parse_options.source_name =
-    jerry_string ((const jerry_char_t *) file_name_p, (jerry_size_t) strlen (file_name_p), JERRY_ENCODING_UTF8);
+    jerry_string_utf8 ((const jerry_char_t *) file_name_p, (jerry_size_t) strlen (file_name_p));
 
   if (function_args_p != NULL)
   {
     parse_options.options |= JERRY_PARSE_HAS_ARGUMENT_LIST;
-    parse_options.argument_list = jerry_string ((const jerry_char_t *) function_args_p,
-                                                (jerry_size_t) strlen (function_args_p),
-                                                JERRY_ENCODING_UTF8);
+    parse_options.argument_list =
+      jerry_string_utf8 ((const jerry_char_t *) function_args_p, (jerry_size_t) strlen (function_args_p));
   }
 
   jerry_value_t snapshot_result = jerry_parse ((jerry_char_t *) source_p, source_length, &parse_options);
diff --git a/jerry-port/common/jerry-port-io.c b/jerry-port/common/jerry-port-io.c
index 26ae7c4445..eaa6633ca7 100644
--- a/jerry-port/common/jerry-port-io.c
+++ b/jerry-port/common/jerry-port-io.c
@@ -19,14 +19,11 @@
 
 #include "jerryscript-port.h"
 
-/**
- * Default implementation of jerry_port_log. Prints log messages to stderr.
- */
 void JERRY_ATTR_WEAK
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  fputs (message_p, stderr);
-} /* jerry_port_log */
+  fwrite (buffer_p, 1, buffer_size, stderr);
+} /* jerry_port_log_buffer */
 
 void JERRY_ATTR_WEAK
 jerry_port_print_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
diff --git a/targets/baremetal-sdk/espressif/main/jerry-main.c b/targets/baremetal-sdk/espressif/main/jerry-main.c
index 192bfef661..bd98905736 100644
--- a/targets/baremetal-sdk/espressif/main/jerry-main.c
+++ b/targets/baremetal-sdk/espressif/main/jerry-main.c
@@ -31,7 +31,7 @@ void app_main()
   jerry_log (JERRY_LOG_LEVEL_DEBUG, "This test run the following script code: %s", script);
 
   /* Register the print function in the global object */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Setup Global scope code */
   ret_value = jerry_parse (script, sizeof (script) - 1, NULL);
diff --git a/targets/baremetal-sdk/espressif/main/jerry-port.c b/targets/baremetal-sdk/espressif/main/jerry-port.c
index 6655b21874..e79dc9cbb2 100644
--- a/targets/baremetal-sdk/espressif/main/jerry-port.c
+++ b/targets/baremetal-sdk/espressif/main/jerry-port.c
@@ -30,14 +30,11 @@
 
 static const char ESP_JS_TAG[] = "JS";
 
-/**
- * Provide log message implementation for the engine.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  ESP_LOGI (ESP_JS_TAG, "%s", message_p);
-} /* jerry_port_log */
+  ESP_LOGI (ESP_JS_TAG, "%s", buffer_p);
+} /* jerry_port_log_buffer */
 
 /**
  * Implementation of jerry_port_fatal.
diff --git a/targets/baremetal-sdk/particle/source/main.cpp b/targets/baremetal-sdk/particle/source/main.cpp
index b5cd6cebac..cb6f95d174 100644
--- a/targets/baremetal-sdk/particle/source/main.cpp
+++ b/targets/baremetal-sdk/particle/source/main.cpp
@@ -79,13 +79,13 @@ init_jerry ()
   jerry_value_t prop_name;
 
   func_obj = jerry_function_external (set_led);
-  prop_name = jerry_string_sz ("setLed");
+  prop_name = jerry_sz_ascii ("setLed");
   jerry_value_free (jerry_object_set (object, prop_name, func_obj));
   jerry_value_free (prop_name);
   jerry_value_free (func_obj);
 
   func_obj = jerry_function_external (js_delay);
-  prop_name = jerry_string_sz ("delay");
+  prop_name = jerry_sz_ascii ("delay");
   jerry_value_free (jerry_object_set (object, prop_name, func_obj));
   jerry_value_free (prop_name);
   jerry_value_free (func_obj);
@@ -94,7 +94,7 @@ init_jerry ()
   jerry_value_t global_object = jerry_current_realm ();
 
   /* Add the JS object to the global context */
-  prop_name = jerry_string_sz ("test");
+  prop_name = jerry_sz_ascii ("test");
   jerry_value_free (jerry_object_set (global_object, prop_name, object));
   jerry_value_free (prop_name);
   jerry_value_free (object);
diff --git a/targets/os/mbedos/jerry-main.cpp b/targets/os/mbedos/jerry-main.cpp
index 4db968513c..d8e6f6789d 100644
--- a/targets/os/mbedos/jerry-main.cpp
+++ b/targets/os/mbedos/jerry-main.cpp
@@ -27,14 +27,15 @@
 #define JERRY_STANDALONE_EXIT_CODE_FAIL (1)
 
 #if MBED_MAJOR_VERSION == 5
-static Serial serial(USBTX, USBRX, 115200);
+static Serial serial (USBTX, USBRX, 115200);
 #elif MBED_MAJOR_VERSION == 6
-static BufferedSerial serial(USBTX, USBRX, 115200);
+static BufferedSerial serial (USBTX, USBRX, 115200);
 #else
 #error Unsupported Mbed OS version.
 #endif
 
-int main()
+int
+main ()
 {
   /* Initialize engine */
   jerry_init (JERRY_INIT_EMPTY);
@@ -43,7 +44,7 @@ int main()
   jerry_log (JERRY_LOG_LEVEL_DEBUG, "This test run the following script code: [%s]\n\n", script);
 
   /* Register the print function in the global object. */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Setup Global scope code */
   jerry_value_t ret_value = jerry_parse (script, sizeof (script) - 1, NULL);
diff --git a/targets/os/mbedos/jerry-port.cpp b/targets/os/mbedos/jerry-port.cpp
index 9ba1383c48..cf7bc6f550 100644
--- a/targets/os/mbedos/jerry-port.cpp
+++ b/targets/os/mbedos/jerry-port.cpp
@@ -29,23 +29,20 @@ jerry_port_fatal (jerry_fatal_code_t code)
   exit ((int) code);
 } /* jerry_port_fatal */
 
-/**
- * Provide log message implementation for the engine.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  while (*message_p != '\0')
+  for (jerry_size_t i = 0; i < buffer_size; ++i)
   {
-    if (*message_p == '\n')
+    if (buffer_p[i] == '\n')
     {
       /* add CR for proper display in serial monitors */
       fputc ('\r', stderr);
     }
 
-    fputc (*message_p++, stderr);
+    fputc (buffer_p[i], stderr);
   }
-} /* jerry_port_log */
+} /* jerry_port_log_buffer */
 
 /**
  * Dummy function to get the time zone adjustment.
diff --git a/targets/os/nuttx/jerry-main.c b/targets/os/nuttx/jerry-main.c
index d09c438355..2f4bf35a58 100644
--- a/targets/os/nuttx/jerry-main.c
+++ b/targets/os/nuttx/jerry-main.c
@@ -96,16 +96,17 @@ str_to_uint (const char *num_str_p, /**< string to convert */
  * Register a JavaScript function in the global object.
  */
 static void
-register_js_function (const char *name_p, /**< name of the function */
+register_js_function (jerry_value_t function_name_val, /**< name of the function that will be free/take */
                       jerry_external_handler_t handler_p) /**< function callback */
 {
-  jerry_value_t result_val = jerryx_register_global (name_p, handler_p);
+  jerry_value_t result_val = jerryx_register_global (jerry_value_copy (function_name_val), handler_p);
 
   if (jerry_value_is_exception (result_val))
   {
-    jerry_log (JERRY_LOG_LEVEL_WARNING, "Warning: failed to register '%s' method.", name_p);
+    jerry_log (JERRY_LOG_LEVEL_WARNING, "Warning: failed to register '%S' method.", function_name_val);
   }
 
+  jerry_value_free (function_name_val);
   jerry_value_free (result_val);
 } /* register_js_function */
 
@@ -197,9 +198,9 @@ jerry_main (int argc, char *argv[])
     jerryx_debugger_after_connect (jerryx_debugger_tcp_create (debug_port) && jerryx_debugger_ws_create ());
   }
 
-  register_js_function ("assert", jerryx_handler_assert);
-  register_js_function ("gc", jerryx_handler_gc);
-  register_js_function ("print", jerryx_handler_print);
+  register_js_function (jerry_sz_ascii("assert"), jerryx_handler_assert);
+  register_js_function (jerry_sz_ascii("gc"), jerryx_handler_gc);
+  register_js_function (jerry_sz_ascii("print"), jerryx_handler_print);
 
   jerry_value_t ret_value = jerry_undefined ();
   int ret_code = JERRY_STANDALONE_EXIT_CODE_OK;
diff --git a/targets/os/nuttx/jerry-port.c b/targets/os/nuttx/jerry-port.c
index c4f65a44a6..f90c918826 100644
--- a/targets/os/nuttx/jerry-port.c
+++ b/targets/os/nuttx/jerry-port.c
@@ -19,14 +19,12 @@
 
 #include "jerryscript-port.h"
 
-/**
- * Default implementation of jerry_port_log. Prints log messages to stderr.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  (void) message_p;
-} /* jerry_port_log */
+  JERRY_UNUSED (buffer_p);
+  JERRY_UNUSED (buffer_size);
+} /* jerry_port_log_buffer */
 
 /**
  * Read a line from standard input as a zero-terminated string.
diff --git a/targets/os/riot/source/jerry-main.c b/targets/os/riot/source/jerry-main.c
index 9ca1583c87..a748820f78 100644
--- a/targets/os/riot/source/jerry-main.c
+++ b/targets/os/riot/source/jerry-main.c
@@ -49,7 +49,7 @@ test_jerry (int argc, char **argv)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Register the print function in the global object. */
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   /* Setup Global scope code */
   ret_value = jerry_parse (script, sizeof (script) - 1, NULL);
diff --git a/targets/os/zephyr/src/jerry-main.c b/targets/os/zephyr/src/jerry-main.c
index 6042fa69fe..79e5b7ef5c 100644
--- a/targets/os/zephyr/src/jerry-main.c
+++ b/targets/os/zephyr/src/jerry-main.c
@@ -47,7 +47,7 @@ main (void)
 
   zephyr_getline_init ();
   jerry_init (JERRY_INIT_EMPTY);
-  jerryx_register_global ("print", jerryx_handler_print);
+  jerryx_register_global (jerry_sz_ascii ("print"), jerryx_handler_print);
 
   jerryx_repl (JERRY_ZSTR_ARG ("js> "));
 
diff --git a/tests/unit-core/test-abort.c b/tests/unit-core/test-abort.c
index e8d3329418..bc3447a141 100644
--- a/tests/unit-core/test-abort.c
+++ b/tests/unit-core/test-abort.c
@@ -25,7 +25,7 @@ callback_func (const jerry_call_info_t *call_info_p, const jerry_value_t args_p[
   JERRY_UNUSED (args_p);
   JERRY_UNUSED (args_count);
 
-  jerry_value_t value = jerry_string_sz ("Abort run!");
+  jerry_value_t value = jerry_sz_ascii ("Abort run!");
   value = jerry_throw_abort (value, true);
   return value;
 } /* callback_func */
@@ -38,7 +38,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t global = jerry_current_realm ();
-  jerry_value_t callback_name = jerry_string_sz ("callback");
+  jerry_value_t callback_name = jerry_sz_ascii ("callback");
   jerry_value_t func = jerry_function_external (callback_func);
   jerry_value_t res = jerry_object_set (global, callback_name, func);
   TEST_ASSERT (!jerry_value_is_exception (res));
@@ -98,7 +98,7 @@ main (void)
   jerry_value_free (parsed_code_val);
 
   /* Test flag overwrites. */
-  jerry_value_t value = jerry_string_sz ("Error description");
+  jerry_value_t value = jerry_sz_ascii ("Error description");
   TEST_ASSERT (!jerry_value_is_abort (value));
   TEST_ASSERT (!jerry_value_is_exception (value));
 
diff --git a/tests/unit-core/test-api-binary-operations-arithmetics.c b/tests/unit-core/test-api-binary-operations-arithmetics.c
index 185dc12c01..f277512b6a 100644
--- a/tests/unit-core/test-api-binary-operations-arithmetics.c
+++ b/tests/unit-core/test-api-binary-operations-arithmetics.c
@@ -59,7 +59,7 @@ main (void)
 
   jerry_value_t obj1 = jerry_eval ((jerry_char_t *) "o={x:1};o", 9, JERRY_PARSE_NO_OPTS);
   jerry_value_t obj2 = jerry_eval ((jerry_char_t *) "o={x:1};o", 9, JERRY_PARSE_NO_OPTS);
-  jerry_value_t err1 = jerry_throw_sz (JERRY_ERROR_SYNTAX, "error");
+  jerry_value_t err1 = jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("error"));
 
   test_nan_entry_t test_nans[] = {
     /* Testing addition (+) */
@@ -69,13 +69,13 @@ main (void)
 
     /* Testing subtraction (-), multiplication (*), division (/), remainder (%) */
     T_ARI (jerry_number (3.1), jerry_undefined ()),
-    T_ARI (jerry_string_sz ("foo"), jerry_string_sz ("bar")),
-    T_ARI (jerry_string_sz ("foo"), jerry_undefined ()),
-    T_ARI (jerry_string_sz ("foo"), jerry_null ()),
-    T_ARI (jerry_string_sz ("foo"), jerry_number (5.0)),
-    T_ARI (jerry_undefined (), jerry_string_sz ("foo")),
-    T_ARI (jerry_null (), jerry_string_sz ("foo")),
-    T_ARI (jerry_number (5.0), jerry_string_sz ("foo")),
+    T_ARI (jerry_sz_ascii ("foo"), jerry_sz_ascii ("bar")),
+    T_ARI (jerry_sz_ascii ("foo"), jerry_undefined ()),
+    T_ARI (jerry_sz_ascii ("foo"), jerry_null ()),
+    T_ARI (jerry_sz_ascii ("foo"), jerry_number (5.0)),
+    T_ARI (jerry_undefined (), jerry_sz_ascii ("foo")),
+    T_ARI (jerry_null (), jerry_sz_ascii ("foo")),
+    T_ARI (jerry_number (5.0), jerry_sz_ascii ("foo")),
     T_ARI (jerry_undefined (), jerry_undefined ()),
     T_ARI (jerry_undefined (), jerry_null ()),
     T_ARI (jerry_null (), jerry_undefined ()),
@@ -83,7 +83,7 @@ main (void)
     T_ARI (jerry_value_copy (obj1), jerry_value_copy (obj2)),
     T_ARI (jerry_value_copy (obj2), jerry_value_copy (obj1)),
     T_ARI (jerry_value_copy (obj2), jerry_undefined ()),
-    T_ARI (jerry_value_copy (obj1), jerry_string_sz ("foo")),
+    T_ARI (jerry_value_copy (obj1), jerry_sz_ascii ("foo")),
     T_ARI (jerry_value_copy (obj1), jerry_null ()),
     T_ARI (jerry_value_copy (obj1), jerry_boolean (true)),
     T_ARI (jerry_value_copy (obj1), jerry_boolean (false)),
@@ -120,10 +120,10 @@ main (void)
     T (JERRY_BIN_OP_ADD, jerry_number (5.0), jerry_number (5.0), jerry_number (10.0)),
     T (JERRY_BIN_OP_ADD, jerry_number (3.1), jerry_number (10), jerry_number (13.1)),
     T (JERRY_BIN_OP_ADD, jerry_number (3.1), jerry_boolean (true), jerry_number (4.1)),
-    T (JERRY_BIN_OP_ADD, jerry_string_sz ("foo"), jerry_string_sz ("bar"), jerry_string_sz ("foobar")),
-    T (JERRY_BIN_OP_ADD, jerry_string_sz ("foo"), jerry_undefined (), jerry_string_sz ("fooundefined")),
-    T (JERRY_BIN_OP_ADD, jerry_string_sz ("foo"), jerry_null (), jerry_string_sz ("foonull")),
-    T (JERRY_BIN_OP_ADD, jerry_string_sz ("foo"), jerry_number (5.0), jerry_string_sz ("foo5")),
+    T (JERRY_BIN_OP_ADD, jerry_sz_ascii ("foo"), jerry_sz_ascii ("bar"), jerry_sz_ascii ("foobar")),
+    T (JERRY_BIN_OP_ADD, jerry_sz_ascii ("foo"), jerry_undefined (), jerry_sz_ascii ("fooundefined")),
+    T (JERRY_BIN_OP_ADD, jerry_sz_ascii ("foo"), jerry_null (), jerry_sz_ascii ("foonull")),
+    T (JERRY_BIN_OP_ADD, jerry_sz_ascii ("foo"), jerry_number (5.0), jerry_sz_ascii ("foo5")),
 
     T (JERRY_BIN_OP_ADD, jerry_null (), jerry_null (), jerry_number (0.0)),
     T (JERRY_BIN_OP_ADD, jerry_boolean (true), jerry_boolean (true), jerry_number (2.0)),
@@ -133,21 +133,21 @@ main (void)
     T (JERRY_BIN_OP_ADD,
        jerry_value_copy (obj1),
        jerry_value_copy (obj1),
-       jerry_string_sz ("[object Object][object Object]")),
+       jerry_sz_ascii ("[object Object][object Object]")),
     T (JERRY_BIN_OP_ADD,
        jerry_value_copy (obj1),
        jerry_value_copy (obj2),
-       jerry_string_sz ("[object Object][object Object]")),
+       jerry_sz_ascii ("[object Object][object Object]")),
     T (JERRY_BIN_OP_ADD,
        jerry_value_copy (obj2),
        jerry_value_copy (obj1),
-       jerry_string_sz ("[object Object][object Object]")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_null (), jerry_string_sz ("[object Object]null")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_undefined (), jerry_string_sz ("[object Object]undefined")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_boolean (true), jerry_string_sz ("[object Object]true")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_boolean (false), jerry_string_sz ("[object Object]false")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_number (5.0), jerry_string_sz ("[object Object]5")),
-    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_string_sz ("foo"), jerry_string_sz ("[object Object]foo")),
+       jerry_sz_ascii ("[object Object][object Object]")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_null (), jerry_sz_ascii ("[object Object]null")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_undefined (), jerry_sz_ascii ("[object Object]undefined")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_boolean (true), jerry_sz_ascii ("[object Object]true")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_boolean (false), jerry_sz_ascii ("[object Object]false")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_number (5.0), jerry_sz_ascii ("[object Object]5")),
+    T (JERRY_BIN_OP_ADD, jerry_value_copy (obj1), jerry_sz_ascii ("foo"), jerry_sz_ascii ("[object Object]foo")),
 
     /* Testing subtraction (-) */
     T (JERRY_BIN_OP_SUB, jerry_number (5.0), jerry_number (5.0), jerry_number (0.0)),
@@ -221,7 +221,7 @@ main (void)
     T_ERR (JERRY_BIN_OP_ADD, jerry_value_copy (obj3), jerry_boolean (true)),
     T_ERR (JERRY_BIN_OP_ADD, jerry_value_copy (obj3), jerry_boolean (false)),
     T_ERR (JERRY_BIN_OP_ADD, jerry_value_copy (obj3), jerry_value_copy (obj2)),
-    T_ERR (JERRY_BIN_OP_ADD, jerry_value_copy (obj3), jerry_string_sz ("foo")),
+    T_ERR (JERRY_BIN_OP_ADD, jerry_value_copy (obj3), jerry_sz_ascii ("foo")),
 
     /* Testing subtraction (-), multiplication (*), division (/), remainder (%) */
     T_ARI (jerry_value_copy (obj3), jerry_undefined ()),
@@ -229,7 +229,7 @@ main (void)
     T_ARI (jerry_value_copy (obj3), jerry_boolean (true)),
     T_ARI (jerry_value_copy (obj3), jerry_boolean (false)),
     T_ARI (jerry_value_copy (obj3), jerry_value_copy (obj2)),
-    T_ARI (jerry_value_copy (obj3), jerry_string_sz ("foo")),
+    T_ARI (jerry_value_copy (obj3), jerry_sz_ascii ("foo")),
   };
 
   for (uint32_t idx = 0; idx < sizeof (error_tests) / sizeof (test_error_entry_t); idx++)
diff --git a/tests/unit-core/test-api-binary-operations-comparisons.c b/tests/unit-core/test-api-binary-operations-comparisons.c
index 7feb322e1e..b5ad36dc55 100644
--- a/tests/unit-core/test-api-binary-operations-comparisons.c
+++ b/tests/unit-core/test-api-binary-operations-comparisons.c
@@ -39,7 +39,7 @@ main (void)
 
   jerry_value_t obj1 = jerry_eval ((const jerry_char_t *) "o={x:1};o", 9, JERRY_PARSE_NO_OPTS);
   jerry_value_t obj2 = jerry_eval ((const jerry_char_t *) "o={x:1};o", 9, JERRY_PARSE_NO_OPTS);
-  jerry_value_t err1 = jerry_throw_sz (JERRY_ERROR_SYNTAX, "error");
+  jerry_value_t err1 = jerry_throw_sz (JERRY_ERROR_SYNTAX, jerry_sz_ascii ("error"));
 
   test_entry_t tests[] = {
     /* Testing strict equal comparison */
@@ -47,10 +47,10 @@ main (void)
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_number (3.1), jerry_number (10), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_number (3.1), jerry_boolean (true), false),
-    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_string_sz ("example string"), jerry_string_sz ("example string"), true),
-    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_string_sz ("example string"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_string_sz ("example string"), jerry_null (), false),
-    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_string_sz ("example string"), jerry_number (5.0), false),
+    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_sz_ascii ("example string"), jerry_sz_ascii ("example string"), true),
+    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_sz_ascii ("example string"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_sz_ascii ("example string"), jerry_null (), false),
+    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_sz_ascii ("example string"), jerry_number (5.0), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_undefined (), jerry_undefined (), true),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_undefined (), jerry_null (), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_null (), jerry_null (), true),
@@ -66,17 +66,17 @@ main (void)
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_value_copy (obj1), jerry_boolean (true), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_value_copy (obj1), jerry_boolean (false), false),
     T (JERRY_BIN_OP_STRICT_EQUAL, jerry_value_copy (obj1), jerry_number (5.0), false),
-    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_value_copy (obj1), jerry_string_sz ("example string"), false),
+    T (JERRY_BIN_OP_STRICT_EQUAL, jerry_value_copy (obj1), jerry_sz_ascii ("example string"), false),
 
     /* Testing equal comparison */
     T (JERRY_BIN_OP_EQUAL, jerry_number (5.0), jerry_number (5.0), true),
     T (JERRY_BIN_OP_EQUAL, jerry_number (3.1), jerry_number (10), false),
     T (JERRY_BIN_OP_EQUAL, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_EQUAL, jerry_number (3.1), jerry_boolean (true), false),
-    T (JERRY_BIN_OP_EQUAL, jerry_string_sz ("example string"), jerry_string_sz ("example string"), true),
-    T (JERRY_BIN_OP_EQUAL, jerry_string_sz ("example string"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_EQUAL, jerry_string_sz ("example string"), jerry_null (), false),
-    T (JERRY_BIN_OP_EQUAL, jerry_string_sz ("example string"), jerry_number (5.0), false),
+    T (JERRY_BIN_OP_EQUAL, jerry_sz_ascii ("example string"), jerry_sz_ascii ("example string"), true),
+    T (JERRY_BIN_OP_EQUAL, jerry_sz_ascii ("example string"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_EQUAL, jerry_sz_ascii ("example string"), jerry_null (), false),
+    T (JERRY_BIN_OP_EQUAL, jerry_sz_ascii ("example string"), jerry_number (5.0), false),
     T (JERRY_BIN_OP_EQUAL, jerry_undefined (), jerry_undefined (), true),
     T (JERRY_BIN_OP_EQUAL, jerry_undefined (), jerry_null (), true),
     T (JERRY_BIN_OP_EQUAL, jerry_null (), jerry_null (), true),
@@ -92,17 +92,17 @@ main (void)
     T (JERRY_BIN_OP_EQUAL, jerry_value_copy (obj1), jerry_boolean (true), false),
     T (JERRY_BIN_OP_EQUAL, jerry_value_copy (obj1), jerry_boolean (false), false),
     T (JERRY_BIN_OP_EQUAL, jerry_value_copy (obj1), jerry_number (5.0), false),
-    T (JERRY_BIN_OP_EQUAL, jerry_value_copy (obj1), jerry_string_sz ("example string"), false),
+    T (JERRY_BIN_OP_EQUAL, jerry_value_copy (obj1), jerry_sz_ascii ("example string"), false),
 
     /* Testing less comparison */
     T (JERRY_BIN_OP_LESS, jerry_number (5.0), jerry_number (5.0), false),
     T (JERRY_BIN_OP_LESS, jerry_number (3.1), jerry_number (10), true),
     T (JERRY_BIN_OP_LESS, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_LESS, jerry_number (3.1), jerry_boolean (true), false),
-    T (JERRY_BIN_OP_LESS, jerry_string_sz ("1"), jerry_string_sz ("2"), true),
-    T (JERRY_BIN_OP_LESS, jerry_string_sz ("1"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_LESS, jerry_string_sz ("1"), jerry_null (), false),
-    T (JERRY_BIN_OP_LESS, jerry_string_sz ("1"), jerry_number (5.0), true),
+    T (JERRY_BIN_OP_LESS, jerry_sz_ascii ("1"), jerry_sz_ascii ("2"), true),
+    T (JERRY_BIN_OP_LESS, jerry_sz_ascii ("1"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_LESS, jerry_sz_ascii ("1"), jerry_null (), false),
+    T (JERRY_BIN_OP_LESS, jerry_sz_ascii ("1"), jerry_number (5.0), true),
     T (JERRY_BIN_OP_LESS, jerry_undefined (), jerry_undefined (), false),
     T (JERRY_BIN_OP_LESS, jerry_undefined (), jerry_null (), false),
     T (JERRY_BIN_OP_LESS, jerry_null (), jerry_null (), false),
@@ -117,12 +117,12 @@ main (void)
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_number (3.1), jerry_number (10), true),
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_number (3.1), jerry_boolean (true), false),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("1"), jerry_string_sz ("2"), true),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("1"), jerry_string_sz ("1"), true),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("1"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("1"), jerry_null (), false),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("1"), jerry_number (5.0), true),
-    T (JERRY_BIN_OP_LESS_EQUAL, jerry_string_sz ("5.0"), jerry_number (5.0), true),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("1"), jerry_sz_ascii ("2"), true),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("1"), jerry_sz_ascii ("1"), true),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("1"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("1"), jerry_null (), false),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("1"), jerry_number (5.0), true),
+    T (JERRY_BIN_OP_LESS_EQUAL, jerry_sz_ascii ("5.0"), jerry_number (5.0), true),
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_undefined (), jerry_undefined (), false),
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_undefined (), jerry_null (), false),
     T (JERRY_BIN_OP_LESS_EQUAL, jerry_null (), jerry_null (), true),
@@ -136,11 +136,11 @@ main (void)
     T (JERRY_BIN_OP_GREATER, jerry_number (10), jerry_number (3.1), true),
     T (JERRY_BIN_OP_GREATER, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_GREATER, jerry_number (3.1), jerry_boolean (true), true),
-    T (JERRY_BIN_OP_GREATER, jerry_string_sz ("2"), jerry_string_sz ("1"), true),
-    T (JERRY_BIN_OP_GREATER, jerry_string_sz ("1"), jerry_string_sz ("2"), false),
-    T (JERRY_BIN_OP_GREATER, jerry_string_sz ("1"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_GREATER, jerry_string_sz ("1"), jerry_null (), true),
-    T (JERRY_BIN_OP_GREATER, jerry_number (5.0), jerry_string_sz ("1"), true),
+    T (JERRY_BIN_OP_GREATER, jerry_sz_ascii ("2"), jerry_sz_ascii ("1"), true),
+    T (JERRY_BIN_OP_GREATER, jerry_sz_ascii ("1"), jerry_sz_ascii ("2"), false),
+    T (JERRY_BIN_OP_GREATER, jerry_sz_ascii ("1"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_GREATER, jerry_sz_ascii ("1"), jerry_null (), true),
+    T (JERRY_BIN_OP_GREATER, jerry_number (5.0), jerry_sz_ascii ("1"), true),
     T (JERRY_BIN_OP_GREATER, jerry_undefined (), jerry_undefined (), false),
     T (JERRY_BIN_OP_GREATER, jerry_undefined (), jerry_null (), false),
     T (JERRY_BIN_OP_GREATER, jerry_null (), jerry_null (), false),
@@ -155,12 +155,12 @@ main (void)
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_number (10), jerry_number (3.1), true),
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_number (3.1), jerry_undefined (), false),
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_number (3.1), jerry_boolean (true), true),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_string_sz ("2"), jerry_string_sz ("1"), true),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_string_sz ("1"), jerry_string_sz ("1"), true),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_string_sz ("1"), jerry_undefined (), false),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_string_sz ("1"), jerry_null (), true),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_number (5.0), jerry_string_sz ("1"), true),
-    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_string_sz ("5.0"), jerry_number (5.0), true),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_sz_ascii ("2"), jerry_sz_ascii ("1"), true),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_sz_ascii ("1"), jerry_sz_ascii ("1"), true),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_sz_ascii ("1"), jerry_undefined (), false),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_sz_ascii ("1"), jerry_null (), true),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_number (5.0), jerry_sz_ascii ("1"), true),
+    T (JERRY_BIN_OP_GREATER_EQUAL, jerry_sz_ascii ("5.0"), jerry_number (5.0), true),
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_undefined (), jerry_undefined (), false),
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_undefined (), jerry_null (), false),
     T (JERRY_BIN_OP_GREATER_EQUAL, jerry_null (), jerry_null (), true),
diff --git a/tests/unit-core/test-api-binary-operations-instanceof.c b/tests/unit-core/test-api-binary-operations-instanceof.c
index 2a2043961d..1e59ce362c 100644
--- a/tests/unit-core/test-api-binary-operations-instanceof.c
+++ b/tests/unit-core/test-api-binary-operations-instanceof.c
@@ -52,7 +52,7 @@ main (void)
 
   jerry_value_t no_proto_instance_val = jerry_construct (constructor, NULL, 0);
 
-  jerry_value_t prototype_str = jerry_string_sz ("prototype");
+  jerry_value_t prototype_str = jerry_sz_ascii ("prototype");
   jerry_value_t res = jerry_object_set (constructor, prototype_str, base_obj);
   jerry_value_free (prototype_str);
   TEST_ASSERT (!jerry_value_is_exception (res));
@@ -82,14 +82,14 @@ main (void)
                                  T (jerry_value_copy (instance_val), jerry_value_copy (base_obj), true),
                                  T (jerry_value_copy (error), jerry_value_copy (constructor), true),
                                  T (jerry_value_copy (instance_val), jerry_value_copy (error), true),
-                                 T (jerry_string_sz (""), jerry_string_sz (""), true),
-                                 T (jerry_string_sz (""), jerry_number (5.0), true),
-                                 T (jerry_number (5.0), jerry_string_sz (""), true),
+                                 T (jerry_sz_ascii (""), jerry_sz_ascii (""), true),
+                                 T (jerry_sz_ascii (""), jerry_number (5.0), true),
+                                 T (jerry_number (5.0), jerry_sz_ascii (""), true),
                                  T (jerry_array (1), jerry_array (1), true),
                                  T (jerry_array (1), jerry_object (), true),
                                  T (jerry_object (), jerry_array (1), true),
                                  T (jerry_null (), jerry_object (), true),
-                                 T (jerry_object (), jerry_string_sz (""), true) };
+                                 T (jerry_object (), jerry_sz_ascii (""), true) };
 
   for (uint32_t idx = 0; idx < sizeof (error_tests) / sizeof (test_entry_t); idx++)
   {
diff --git a/tests/unit-core/test-api-errortype.c b/tests/unit-core/test-api-errortype.c
index 43327e8f2b..5125ca2f63 100644
--- a/tests/unit-core/test-api-errortype.c
+++ b/tests/unit-core/test-api-errortype.c
@@ -29,7 +29,7 @@ main (void)
 
   for (size_t idx = 0; idx < sizeof (errors) / sizeof (errors[0]); idx++)
   {
-    jerry_value_t error_obj = jerry_throw_sz (errors[idx], "test");
+    jerry_value_t error_obj = jerry_throw_sz (errors[idx], jerry_sz_ascii ("test"));
     TEST_ASSERT (jerry_value_is_exception (error_obj));
     TEST_ASSERT (jerry_error_type (error_obj) == errors[idx]);
 
@@ -42,7 +42,7 @@ main (void)
 
   jerry_value_t test_values[] = {
     jerry_number (11),
-    jerry_string_sz ("message"),
+    jerry_sz_ascii ("message"),
     jerry_boolean (true),
     jerry_object (),
   };
diff --git a/tests/unit-core/test-api-functiontype.c b/tests/unit-core/test-api-functiontype.c
index 6792e5a6fa..de3989c5e6 100644
--- a/tests/unit-core/test-api-functiontype.c
+++ b/tests/unit-core/test-api-functiontype.c
@@ -70,8 +70,8 @@ main (void)
     ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_boolean (true)),
     ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_undefined ()),
     ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_null ()),
-    ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_string_sz ("foo")),
-    ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, "error")),
+    ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_sz_ascii ("foo")),
+    ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"))),
 
     ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_object ()),
     ENTRY (JERRY_FUNCTION_TYPE_NONE, jerry_array (10)),
diff --git a/tests/unit-core/test-api-iteratortype.c b/tests/unit-core/test-api-iteratortype.c
index 262212ec15..21a38c072e 100644
--- a/tests/unit-core/test-api-iteratortype.c
+++ b/tests/unit-core/test-api-iteratortype.c
@@ -69,8 +69,8 @@ main (void)
     ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_boolean (true)),
     ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_undefined ()),
     ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_null ()),
-    ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_string_sz ("foo")),
-    ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, "error")),
+    ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_sz_ascii ("foo")),
+    ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"))),
 
     ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_object ()),
     ENTRY (JERRY_ITERATOR_TYPE_NONE, jerry_array (10)),
diff --git a/tests/unit-core/test-api-object-property-names.c b/tests/unit-core/test-api-object-property-names.c
index 2bbe08bb97..b5c735459b 100644
--- a/tests/unit-core/test-api-object-property-names.c
+++ b/tests/unit-core/test-api-object-property-names.c
@@ -18,14 +18,12 @@
 
 #include "test-common.h"
 
-static const char *prop_names[] = { "val1", "val2", "val3", "val4", "val5", "37", "symbol" };
-
 static jerry_char_t buffer[256] = { 0 };
+static jerry_char_t buffer_prop_name[256] = { 0 };
 
 static void
-create_and_set_property (const jerry_value_t object, const char *prop_name)
+create_and_set_property (const jerry_value_t object, jerry_value_t jprop_name)
 {
-  jerry_value_t jprop_name = jerry_string_sz (prop_name);
   jerry_value_t ret_val = jerry_object_set (object, jprop_name, jerry_undefined ());
 
   jerry_value_free (jprop_name);
@@ -33,8 +31,16 @@ create_and_set_property (const jerry_value_t object, const char *prop_name)
 } /* create_and_set_property */
 
 static void
-compare_prop_name (const jerry_value_t object, const char *prop_name, uint32_t idx)
+compare_prop_name (const jerry_value_t object, const jerry_value_t prop_name_value, uint32_t idx)
 {
+  {
+    jerry_size_t prop_name_size = jerry_string_size (prop_name_value, JERRY_ENCODING_CESU8);
+    TEST_ASSERT (prop_name_size < sizeof (buffer_prop_name));
+    jerry_size_t ret_size =
+      jerry_string_to_buffer (prop_name_value, JERRY_ENCODING_CESU8, buffer_prop_name, prop_name_size);
+    TEST_ASSERT (prop_name_size == ret_size);
+    buffer_prop_name[prop_name_size] = '\0';
+  }
   jerry_value_t name = jerry_object_get_index (object, idx);
   TEST_ASSERT (jerry_value_is_string (name) || jerry_value_is_number (name));
   if (jerry_value_is_string (name))
@@ -44,23 +50,22 @@ compare_prop_name (const jerry_value_t object, const char *prop_name, uint32_t i
     jerry_size_t ret_size = jerry_string_to_buffer (name, JERRY_ENCODING_CESU8, buffer, sizeof (buffer));
     TEST_ASSERT (name_size == ret_size);
     buffer[name_size] = '\0';
-    TEST_ASSERT (strcmp ((const char *) buffer, prop_name) == 0);
+    TEST_ASSERT (strcmp ((const char *) buffer, (const char *) buffer_prop_name) == 0);
   }
   else
   {
-    TEST_ASSERT ((int) jerry_value_as_number (name) == atoi (prop_name));
+    TEST_ASSERT ((int) jerry_value_as_number (name) == atoi ((const char *) buffer_prop_name));
   }
 
   jerry_value_free (name);
 } /* compare_prop_name */
 
 static void
-define_property (const jerry_value_t object,
-                 const char *prop_name,
+define_property (const jerry_value_t object, /**< object value */
+                 jerry_value_t jname, /**< property name that will be free/take*/
                  jerry_property_descriptor_t *prop_desc_p,
                  bool is_symbol)
 {
-  jerry_value_t jname = jerry_string_sz (prop_name);
   jerry_value_t ret_val;
   if (is_symbol)
   {
@@ -87,6 +92,10 @@ main (void)
   TEST_ASSERT (jerry_value_is_exception (error_value) && jerry_error_type (error_value) == JERRY_ERROR_TYPE);
   jerry_value_free (error_value);
 
+  jerry_value_t prop_names[] = { jerry_sz_ascii ("val1"),  jerry_sz_ascii ("val2"), jerry_sz_ascii ("val3"),
+                                 jerry_sz_ascii ("val4"),  jerry_sz_ascii ("val5"), jerry_sz_ascii ("37"),
+                                 jerry_sz_ascii ("symbol") };
+
   jerry_value_t test_object = jerry_object ();
   create_and_set_property (test_object, prop_names[0]);
   create_and_set_property (test_object, prop_names[1]);
diff --git a/tests/unit-core/test-api-objecttype.c b/tests/unit-core/test-api-objecttype.c
index 0e35c8fc78..734699a03f 100644
--- a/tests/unit-core/test-api-objecttype.c
+++ b/tests/unit-core/test-api-objecttype.c
@@ -112,8 +112,8 @@ main (void)
     ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_boolean (true)),
     ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_undefined ()),
     ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_null ()),
-    ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_string_sz ("foo")),
-    ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, "error")),
+    ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_sz_ascii ("foo")),
+    ENTRY (JERRY_OBJECT_TYPE_NONE, jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"))),
 
     ENTRY (JERRY_OBJECT_TYPE_GENERIC, jerry_object ()),
     ENTRY_IF (JERRY_OBJECT_TYPE_MODULE_NAMESPACE, test_namespace (module_parse_options), JERRY_FEATURE_MODULE),
diff --git a/tests/unit-core/test-api-promise.c b/tests/unit-core/test-api-promise.c
index 1b8d86bd8a..3612984216 100644
--- a/tests/unit-core/test-api-promise.c
+++ b/tests/unit-core/test-api-promise.c
@@ -36,7 +36,7 @@ test_promise_resolve_success (void)
 
   jerry_value_t resolve_value = jerry_object ();
   {
-    jerry_value_t obj_key = jerry_string_sz ("key_one");
+    jerry_value_t obj_key = jerry_sz_ascii ("key_one");
     jerry_value_t set_result = jerry_object_set (resolve_value, obj_key, jerry_number (3));
     TEST_ASSERT (jerry_value_is_boolean (set_result) && (jerry_value_is_true (set_result)));
     jerry_value_free (set_result);
@@ -53,7 +53,7 @@ test_promise_resolve_success (void)
     jerry_value_t promise_result = jerry_promise_result (my_promise);
     {
       TEST_ASSERT (jerry_value_is_object (promise_result));
-      jerry_value_t obj_key = jerry_string_sz ("key_one");
+      jerry_value_t obj_key = jerry_sz_ascii ("key_one");
       jerry_value_t get_result = jerry_object_get (promise_result, obj_key);
       TEST_ASSERT (jerry_value_is_number (get_result));
       TEST_ASSERT (jerry_value_as_number (get_result) == 3.0);
@@ -77,7 +77,7 @@ test_promise_resolve_success (void)
     jerry_value_t promise_result = jerry_promise_result (my_promise);
     {
       TEST_ASSERT (jerry_value_is_object (promise_result));
-      jerry_value_t obj_key = jerry_string_sz ("key_one");
+      jerry_value_t obj_key = jerry_sz_ascii ("key_one");
       jerry_value_t get_result = jerry_object_get (promise_result, obj_key);
       TEST_ASSERT (jerry_value_is_number (get_result));
       TEST_ASSERT (jerry_value_as_number (get_result) == 3.0);
@@ -115,7 +115,7 @@ test_promise_resolve_fail (void)
 
   // A resolved promise should have the result of from the resolve call and a fulfilled state
   {
-    jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_TYPE, "resolve_fail");
+    jerry_value_t error_obj = jerry_error_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("resolve_fail"));
     jerry_value_t resolve_result = jerry_promise_reject (my_promise, error_obj);
     jerry_value_free (error_obj);
 
diff --git a/tests/unit-core/test-api-property.c b/tests/unit-core/test-api-property.c
index 2315003bb9..5019abd190 100644
--- a/tests/unit-core/test-api-property.c
+++ b/tests/unit-core/test-api-property.c
@@ -33,7 +33,7 @@ main (void)
 
   /* Test: define own properties */
   jerry_value_t global_obj_val = jerry_current_realm ();
-  jerry_value_t prop_name = jerry_string_sz ("my_defined_property");
+  jerry_value_t prop_name = jerry_sz_ascii ("my_defined_property");
   prop_desc.flags |= JERRY_PROP_IS_VALUE_DEFINED;
   prop_desc.value = jerry_value_copy (prop_name);
   jerry_value_t res = jerry_object_define_own_prop (global_obj_val, prop_name, &prop_desc);
@@ -96,7 +96,7 @@ main (void)
 
   /* Test: define and get own property descriptor */
   prop_desc.flags |= JERRY_PROP_IS_ENUMERABLE;
-  prop_name = jerry_string_sz ("enumerable-property");
+  prop_name = jerry_sz_ascii ("enumerable-property");
   res = jerry_object_define_own_prop (global_obj_val, prop_name, &prop_desc);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_boolean (res));
@@ -119,7 +119,7 @@ main (void)
   prop_desc.value = jerry_number (11);
 
   jerry_value_t obj_val = jerry_object ();
-  prop_name = jerry_string_sz ("property_key");
+  prop_name = jerry_sz_ascii ("property_key");
   res = jerry_object_define_own_prop (obj_val, prop_name, &prop_desc);
   TEST_ASSERT (!jerry_value_is_exception (res));
   jerry_value_free (res);
diff --git a/tests/unit-core/test-api-set-and-clear-error-flag.c b/tests/unit-core/test-api-set-and-clear-error-flag.c
index e4fdb5a407..397c84d01d 100644
--- a/tests/unit-core/test-api-set-and-clear-error-flag.c
+++ b/tests/unit-core/test-api-set-and-clear-error-flag.c
@@ -44,17 +44,17 @@ main (void)
   jerry_value_free (err_val);
   jerry_value_free (obj_val);
 
-  const char pterodactylus[] = "Pterodactylus";
+#define pterodactylus "Pterodactylus"
   const size_t pterodactylus_size = sizeof (pterodactylus) - 1;
 
-  jerry_value_t str = jerry_string_sz (pterodactylus);
+  jerry_value_t str = jerry_sz_ascii (pterodactylus);
   jerry_value_t error = jerry_throw_value (str, true);
   str = jerry_exception_value (error, true);
 
   compare_str (str, pterodactylus, pterodactylus_size);
   jerry_value_free (str);
 
-  str = jerry_string_sz (pterodactylus);
+  str = jerry_sz_ascii (pterodactylus);
   error = jerry_throw_value (str, false);
   jerry_value_free (str);
   str = jerry_exception_value (error, true);
@@ -62,14 +62,14 @@ main (void)
   compare_str (str, pterodactylus, pterodactylus_size);
   jerry_value_free (str);
 
-  str = jerry_string_sz (pterodactylus);
+  str = jerry_sz_ascii (pterodactylus);
   error = jerry_throw_abort (str, true);
   str = jerry_exception_value (error, true);
 
   compare_str (str, pterodactylus, pterodactylus_size);
   jerry_value_free (str);
 
-  str = jerry_string_sz (pterodactylus);
+  str = jerry_sz_ascii (pterodactylus);
   error = jerry_throw_abort (str, false);
   jerry_value_free (str);
   str = jerry_exception_value (error, true);
@@ -77,7 +77,7 @@ main (void)
   compare_str (str, pterodactylus, pterodactylus_size);
   jerry_value_free (str);
 
-  str = jerry_string_sz (pterodactylus);
+  str = jerry_sz_ascii (pterodactylus);
   error = jerry_throw_value (str, true);
   error = jerry_throw_abort (error, true);
   TEST_ASSERT (jerry_value_is_abort (error));
@@ -86,7 +86,7 @@ main (void)
   compare_str (str, pterodactylus, pterodactylus_size);
   jerry_value_free (str);
 
-  str = jerry_string_sz (pterodactylus);
+  str = jerry_sz_ascii (pterodactylus);
   error = jerry_throw_value (str, true);
   jerry_value_t error2 = jerry_throw_abort (error, false);
   TEST_ASSERT (jerry_value_is_abort (error2));
diff --git a/tests/unit-core/test-api-strings.c b/tests/unit-core/test-api-strings.c
index 4722a8e60a..876e1ecc06 100644
--- a/tests/unit-core/test-api-strings.c
+++ b/tests/unit-core/test-api-strings.c
@@ -44,7 +44,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Test corner case for jerry_string_to_char_buffer */
-  args[0] = jerry_string_sz ("");
+  args[0] = jerry_sz_ascii ("");
   sz = jerry_string_size (args[0], JERRY_ENCODING_CESU8);
   TEST_ASSERT (sz == 0);
   jerry_value_free (args[0]);
@@ -143,7 +143,7 @@ main (void)
 
   /* Test string: '3' */
   {
-    jerry_value_t test_str = jerry_string_sz ("3");
+    jerry_value_t test_str = jerry_sz_ascii ("3");
     char result_string[1] = { 'E' };
     jerry_size_t copied_utf8 =
       jerry_string_to_buffer (test_str, JERRY_ENCODING_UTF8, (jerry_char_t *) result_string, sizeof (result_string));
diff --git a/tests/unit-core/test-api-value-type.c b/tests/unit-core/test-api-value-type.c
index 9890c1eada..578c2779f9 100644
--- a/tests/unit-core/test-api-value-type.c
+++ b/tests/unit-core/test-api-value-type.c
@@ -47,7 +47,7 @@ main (void)
 
   jerry_init (JERRY_INIT_EMPTY);
 
-  const char test_eval_function[] = "function demo(a) { return a + 1; }; demo";
+#define test_eval_function "function demo(a) { return a + 1; }; demo"
 
   test_entry_t entries[] = {
     ENTRY (JERRY_TYPE_NUMBER, jerry_number (-33.0)),
@@ -63,7 +63,7 @@ main (void)
 
     ENTRY (JERRY_TYPE_OBJECT, jerry_object ()),
     ENTRY (JERRY_TYPE_OBJECT, jerry_array (10)),
-    ENTRY (JERRY_TYPE_EXCEPTION, jerry_throw_sz (JERRY_ERROR_TYPE, "error")),
+    ENTRY (JERRY_TYPE_EXCEPTION, jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"))),
 
     ENTRY (JERRY_TYPE_NULL, jerry_null ()),
 
@@ -71,8 +71,8 @@ main (void)
            jerry_eval ((jerry_char_t *) test_eval_function, sizeof (test_eval_function) - 1, JERRY_PARSE_NO_OPTS)),
     ENTRY (JERRY_TYPE_FUNCTION, jerry_function_external (test_ext_function)),
 
-    ENTRY (JERRY_TYPE_STRING, jerry_string_sz (test_eval_function)),
-    ENTRY (JERRY_TYPE_STRING, jerry_string_sz ("")),
+    ENTRY (JERRY_TYPE_STRING, jerry_sz_ascii (test_eval_function)),
+    ENTRY (JERRY_TYPE_STRING, jerry_sz_ascii ("")),
   };
 
   for (size_t idx = 0; idx < sizeof (entries) / sizeof (entries[0]); idx++)
@@ -85,7 +85,7 @@ main (void)
     jerry_value_free (entries[idx].value);
   }
 
-  jerry_value_t symbol_desc_value = jerry_string_sz ("foo");
+  jerry_value_t symbol_desc_value = jerry_sz_ascii ("foo");
   jerry_value_t symbol_value = jerry_symbol_with_description (symbol_desc_value);
   jerry_type_t type_info = jerry_value_type (symbol_value);
 
diff --git a/tests/unit-core/test-api.c b/tests/unit-core/test-api.c
index 6bdc0c4a66..09f2217fd2 100644
--- a/tests/unit-core/test-api.c
+++ b/tests/unit-core/test-api.c
@@ -85,7 +85,7 @@ handler (const jerry_call_info_t *call_info_p, /**< call information */
 
   TEST_ASSERT (jerry_value_is_boolean (args_p[1]));
 
-  return jerry_string_sz ("string from handler");
+  return jerry_sz_ascii ("string from handler");
 } /* handler */
 
 static jerry_value_t
@@ -99,7 +99,7 @@ handler_throw_test (const jerry_call_info_t *call_info_p, /**< call information
           (void *) args_p,
           (unsigned int) args_cnt);
 
-  return jerry_throw_sz (JERRY_ERROR_TYPE, "error");
+  return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"));
 } /* handler_throw_test */
 
 static void
@@ -161,7 +161,7 @@ handler_construct (const jerry_call_info_t *call_info_p, /**< call information *
   TEST_ASSERT (jerry_value_is_true (args_p[0]));
 
   jerry_value_t this_value = call_info_p->this_value;
-  jerry_value_t field_name = jerry_string_sz ("value_field");
+  jerry_value_t field_name = jerry_sz_ascii ("value_field");
   jerry_value_t res = jerry_object_set (this_value, field_name, args_p[0]);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
@@ -310,9 +310,8 @@ foreach_subset (const jerry_value_t name, /**< field name */
 
 static jerry_value_t
 get_property (const jerry_value_t obj_val, /**< object value */
-              const char *str_p) /**< property name */
+              jerry_value_t prop_name_val) /**< property name that will be free/take*/
 {
-  jerry_value_t prop_name_val = jerry_string_sz (str_p);
   jerry_value_t ret_val = jerry_object_get (obj_val, prop_name_val);
   jerry_value_free (prop_name_val);
   return ret_val;
@@ -320,10 +319,9 @@ get_property (const jerry_value_t obj_val, /**< object value */
 
 static jerry_value_t
 set_property (const jerry_value_t obj_val, /**< object value */
-              const char *str_p, /**< property name */
+              jerry_value_t prop_name_val, /**< property name that will be free/take*/
               const jerry_value_t val) /**< value to set */
 {
-  jerry_value_t prop_name_val = jerry_string_sz (str_p);
   jerry_value_t ret_val = jerry_object_set (obj_val, prop_name_val, val);
   jerry_value_free (prop_name_val);
   return ret_val;
@@ -394,18 +392,18 @@ main (void)
   global_obj_val = jerry_current_realm ();
 
   /* Get global.boo (non-existing field) */
-  val_t = get_property (global_obj_val, "boo");
+  val_t = get_property (global_obj_val, jerry_sz_ascii ("boo"));
   TEST_ASSERT (!jerry_value_is_exception (val_t));
   TEST_ASSERT (jerry_value_is_undefined (val_t));
 
   /* Get global.t */
-  val_t = get_property (global_obj_val, "t");
+  val_t = get_property (global_obj_val, jerry_sz_ascii ("t"));
   TEST_ASSERT (!jerry_value_is_exception (val_t));
   TEST_ASSERT (jerry_value_is_number (val_t) && jerry_value_as_number (val_t) == 1.0);
   jerry_value_free (val_t);
 
   /* Get global.foo */
-  val_foo = get_property (global_obj_val, "foo");
+  val_foo = get_property (global_obj_val, jerry_sz_ascii ("foo"));
   TEST_ASSERT (!jerry_value_is_exception (val_foo));
   TEST_ASSERT (jerry_value_is_object (val_foo));
 
@@ -418,7 +416,7 @@ main (void)
   jerry_value_free (res);
 
   /* Get global.bar */
-  val_bar = get_property (global_obj_val, "bar");
+  val_bar = get_property (global_obj_val, jerry_sz_ascii ("bar"));
   TEST_ASSERT (!jerry_value_is_exception (val_bar));
   TEST_ASSERT (jerry_value_is_object (val_bar));
 
@@ -431,8 +429,8 @@ main (void)
 
   /* Set global.t = "abcd" */
   jerry_value_free (args[0]);
-  args[0] = jerry_string_sz ("abcd");
-  res = set_property (global_obj_val, "t", args[0]);
+  args[0] = jerry_sz_ascii ("abcd");
+  res = set_property (global_obj_val, jerry_sz_ascii ("t"), args[0]);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
   jerry_value_free (res);
@@ -451,20 +449,20 @@ main (void)
   jerry_value_free (args[1]);
 
   /* Get global.A */
-  val_A = get_property (global_obj_val, "A");
+  val_A = get_property (global_obj_val, jerry_sz_ascii ("A"));
   TEST_ASSERT (!jerry_value_is_exception (val_A));
   TEST_ASSERT (jerry_value_is_object (val_A));
 
   /* Get A.prototype */
   is_ok = jerry_value_is_constructor (val_A);
   TEST_ASSERT (is_ok);
-  val_A_prototype = get_property (val_A, "prototype");
+  val_A_prototype = get_property (val_A, jerry_sz_ascii ("prototype"));
   TEST_ASSERT (!jerry_value_is_exception (val_A_prototype));
   TEST_ASSERT (jerry_value_is_object (val_A_prototype));
   jerry_value_free (val_A);
 
   /* Set A.prototype.foo = global.foo */
-  res = set_property (val_A_prototype, "foo", val_foo);
+  res = set_property (val_A_prototype, jerry_sz_ascii ("foo"), val_foo);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
   jerry_value_free (res);
@@ -472,18 +470,18 @@ main (void)
   jerry_value_free (val_foo);
 
   /* Get global.a */
-  val_a = get_property (global_obj_val, "a");
+  val_a = get_property (global_obj_val, jerry_sz_ascii ("a"));
   TEST_ASSERT (!jerry_value_is_exception (val_a));
   TEST_ASSERT (jerry_value_is_object (val_a));
 
   /* Get a.t */
-  res = get_property (val_a, "t");
+  res = get_property (val_a, jerry_sz_ascii ("t"));
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_number (res) && jerry_value_as_number (res) == 12.0);
   jerry_value_free (res);
 
   /* foreach properties */
-  val_p = get_property (global_obj_val, "p");
+  val_p = get_property (global_obj_val, jerry_sz_ascii ("p"));
   is_ok = jerry_object_foreach (val_p, foreach, (void *) "user_data");
   TEST_ASSERT (is_ok);
 
@@ -495,13 +493,13 @@ main (void)
   jerry_value_free (val_p);
 
   /* foreach with throw test */
-  val_np = get_property (global_obj_val, "np");
+  val_np = get_property (global_obj_val, jerry_sz_ascii ("np"));
   is_ok = !jerry_object_foreach (val_np, foreach_exception, NULL);
   TEST_ASSERT (is_ok);
   jerry_value_free (val_np);
 
   /* Get a.foo */
-  val_a_foo = get_property (val_a, "foo");
+  val_a_foo = get_property (val_a, jerry_sz_ascii ("foo"));
   TEST_ASSERT (!jerry_value_is_exception (val_a_foo));
   TEST_ASSERT (jerry_value_is_object (val_a_foo));
 
@@ -518,13 +516,13 @@ main (void)
   external_func_val = jerry_function_external (handler);
   TEST_ASSERT (jerry_value_is_function (external_func_val) && jerry_value_is_constructor (external_func_val));
 
-  res = set_property (global_obj_val, "external", external_func_val);
+  res = set_property (global_obj_val, jerry_sz_ascii ("external"), external_func_val);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
   jerry_value_free (external_func_val);
 
   /* Call 'call_external' function that should call external function created above */
-  val_call_external = get_property (global_obj_val, "call_external");
+  val_call_external = get_property (global_obj_val, jerry_sz_ascii ("call_external"));
   TEST_ASSERT (!jerry_value_is_exception (val_call_external));
   TEST_ASSERT (jerry_value_is_object (val_call_external));
   res = jerry_call (val_call_external, global_obj_val, NULL, 0);
@@ -542,7 +540,7 @@ main (void)
   external_construct_val = jerry_function_external (handler_construct);
   TEST_ASSERT (jerry_value_is_function (external_construct_val) && jerry_value_is_constructor (external_construct_val));
 
-  res = set_property (global_obj_val, "external_construct", external_construct_val);
+  res = set_property (global_obj_val, jerry_sz_ascii ("external_construct"), external_construct_val);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
   jerry_value_free (res);
@@ -552,7 +550,7 @@ main (void)
   res = jerry_construct (external_construct_val, args, 1);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_object (res));
-  val_value_field = get_property (res, "value_field");
+  val_value_field = get_property (res, jerry_sz_ascii ("value_field"));
 
   /* Get 'value_field' of constructed object */
   TEST_ASSERT (!jerry_value_is_exception (val_value_field));
@@ -584,13 +582,13 @@ main (void)
   throw_test_handler_val = jerry_function_external (handler_throw_test);
   TEST_ASSERT (jerry_value_is_function (throw_test_handler_val));
 
-  res = set_property (global_obj_val, "throw_test", throw_test_handler_val);
+  res = set_property (global_obj_val, jerry_sz_ascii ("throw_test"), throw_test_handler_val);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_true (res));
   jerry_value_free (res);
   jerry_value_free (throw_test_handler_val);
 
-  val_t = get_property (global_obj_val, "call_throw_test");
+  val_t = get_property (global_obj_val, jerry_sz_ascii ("call_throw_test"));
   TEST_ASSERT (!jerry_value_is_exception (val_t));
   TEST_ASSERT (jerry_value_is_object (val_t));
 
@@ -600,7 +598,7 @@ main (void)
   jerry_value_free (res);
 
   /* Test: Unhandled exception in called function */
-  val_t = get_property (global_obj_val, "throw_reference_error");
+  val_t = get_property (global_obj_val, jerry_sz_ascii ("throw_reference_error"));
   TEST_ASSERT (!jerry_value_is_exception (val_t));
   TEST_ASSERT (jerry_value_is_object (val_t));
 
@@ -627,7 +625,7 @@ main (void)
   jerry_value_free (obj_val);
 
   /* Test: Unhandled exception in function called, as constructor */
-  val_t = get_property (global_obj_val, "throw_reference_error");
+  val_t = get_property (global_obj_val, jerry_sz_ascii ("throw_reference_error"));
   TEST_ASSERT (!jerry_value_is_exception (val_t));
   TEST_ASSERT (jerry_value_is_object (val_t));
 
@@ -805,11 +803,11 @@ main (void)
   jerry_value_free (val_t);
 
   /* Test: create function */
-  jerry_value_t script_source = jerry_string_sz ("  return 5 +  a+\nb+c");
+  jerry_value_t script_source = jerry_sz_ascii ("  return 5 +  a+\nb+c");
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("a , b,c");
+  parse_options.argument_list = jerry_sz_ascii ("a , b,c");
 
   jerry_value_t func_val = jerry_parse_value (script_source, &parse_options);
 
@@ -912,7 +910,7 @@ main (void)
     jerry_value_free (parse_result);
 
     jerry_value_t global_obj = jerry_current_realm ();
-    jerry_value_t prop_name = jerry_string_sz ("foo");
+    jerry_value_t prop_name = jerry_sz_ascii ("foo");
 
     jerry_property_descriptor_t prop_desc = jerry_property_descriptor ();
     prop_desc.flags |= JERRY_PROP_IS_VALUE_DEFINED;
@@ -1005,7 +1003,7 @@ main (void)
                        false);
 
     parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-    parse_options.source_name = jerry_string_sz ("filename.js");
+    parse_options.source_name = jerry_sz_ascii ("filename.js");
 
     test_syntax_error ("b = 'hello';\nvar a = (;",
                        &parse_options,
@@ -1045,9 +1043,9 @@ main (void)
   jerry_value_free (res);
   jerry_value_free (parsed_code_val);
 
-  /* call jerry_string_sz functions which will returns with the registered external magic strings */
-  args[0] = jerry_string_sz ("console");
-  args[1] = jerry_string_sz ("\xed\xa0\x80\xed\xb6\x8a"); /**< greek zero sign */
+  /* call jerry_sz_ascii functions which will returns with the registered external magic strings */
+  args[0] = jerry_sz_ascii ("console");
+  args[1] = jerry_sz_cesu8 ("\xed\xa0\x80\xed\xb6\x8a"); /**< greek zero sign */
 
   cesu8_length = jerry_string_length (args[0]);
   cesu8_sz = jerry_string_size (args[0], JERRY_ENCODING_CESU8);
diff --git a/tests/unit-core/test-arraybuffer.c b/tests/unit-core/test-arraybuffer.c
index c759d72ef0..a78979d9cc 100644
--- a/tests/unit-core/test-arraybuffer.c
+++ b/tests/unit-core/test-arraybuffer.c
@@ -22,12 +22,11 @@
  * Register a JavaScript value in the global object.
  */
 static void
-register_js_value (const char *name_p, /**< name of the function */
+register_js_value (jerry_value_t name_val, /**< name of the function that will be free/take*/
                    jerry_value_t value) /**< JS value */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
-  jerry_value_t name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (global_obj_val, name_val, value);
   TEST_ASSERT (jerry_value_is_boolean (result_val));
 
@@ -105,7 +104,7 @@ test_write_with_offset (uint8_t offset) /**< offset for buffer write. */
 {
   {
     jerry_value_t offset_val = jerry_number (offset);
-    register_js_value ("offset", offset_val);
+    register_js_value (jerry_sz_ascii ("offset"), offset_val);
     jerry_value_free (offset_val);
   }
 
@@ -215,7 +214,7 @@ main (void)
   jerry_arraybuffer_allocator (test_allocate_cb, test_free_cb, (void *) &allocate_mode);
 
   jerry_value_t function_val = jerry_function_external (assert_handler);
-  register_js_value ("assert", function_val);
+  register_js_value (jerry_sz_ascii ("assert"), function_val);
   jerry_value_free (function_val);
 
   /* Test array buffer queries */
@@ -347,7 +346,7 @@ main (void)
     const uint32_t buffer_size = 20;
 
     jerry_value_t input_buffer = jerry_arraybuffer_external (NULL, buffer_size, (void *) &allocate_count);
-    register_js_value ("input_buffer", input_buffer);
+    register_js_value (jerry_sz_ascii ("input_buffer"), input_buffer);
     jerry_value_free (input_buffer);
 
     const jerry_char_t eval_arraybuffer_src[] = TEST_STRING_LITERAL ("var array = new Uint8Array(input_buffer);"
diff --git a/tests/unit-core/test-backtrace.c b/tests/unit-core/test-backtrace.c
index 5e77832b47..08a1ce7381 100644
--- a/tests/unit-core/test-backtrace.c
+++ b/tests/unit-core/test-backtrace.c
@@ -234,12 +234,11 @@ global_capture_handler (const jerry_call_info_t *call_info_p, /**< call informat
 
 static void
 register_callback (jerry_external_handler_t handler_p, /**< callback function */
-                   char *name_p) /**< name of the function */
+                   jerry_value_t name) /**< name of the function that will be free/take */
 {
   jerry_value_t global = jerry_current_realm ();
 
   jerry_value_t func = jerry_function_external (handler_p);
-  jerry_value_t name = jerry_string_sz (name_p);
   jerry_value_t result = jerry_object_set (global, name, func);
   TEST_ASSERT (!jerry_value_is_exception (result));
 
@@ -251,15 +250,15 @@ register_callback (jerry_external_handler_t handler_p, /**< callback function */
 } /* register_callback */
 
 static jerry_value_t
-run (const char *source_name_p, /**< source name */
+run (jerry_value_t source_name, /**< source name that will be free/take */
      const char *source_p) /**< source code */
 {
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz (source_name_p);
+  parse_options.source_name = source_name;
 
   jerry_value_t code = jerry_parse ((const jerry_char_t *) source_p, strlen (source_p), &parse_options);
-  jerry_value_free (parse_options.source_name);
+  jerry_value_free (source_name);
   TEST_ASSERT (!jerry_value_is_exception (code));
 
   jerry_value_t result = jerry_run (code);
@@ -298,8 +297,8 @@ test_get_backtrace_api_call (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  register_callback (backtrace_handler, "backtrace");
-  register_callback (capture_handler, "capture");
+  register_callback (backtrace_handler, jerry_sz_ascii ("backtrace"));
+  register_callback (capture_handler, jerry_sz_ascii ("capture"));
 
   const char *source_p = ("function f() {\n"
                           "  return backtrace(0);\n"
@@ -315,7 +314,7 @@ test_get_backtrace_api_call (void)
                           "\n"
                           "h();\n");
 
-  jerry_value_t backtrace = run ("something.js", source_p);
+  jerry_value_t backtrace = run (jerry_sz_ascii ("something.js"), source_p);
 
   TEST_ASSERT (!jerry_value_is_exception (backtrace) && jerry_value_is_array (backtrace));
 
@@ -344,7 +343,7 @@ test_get_backtrace_api_call (void)
               "\n"
               "h();\n");
 
-  backtrace = run ("something_else.js", source_p);
+  backtrace = run (jerry_sz_ascii ("something_else.js"), source_p);
 
   TEST_ASSERT (!jerry_value_is_exception (backtrace) && jerry_value_is_array (backtrace));
 
@@ -373,7 +372,7 @@ test_get_backtrace_api_call (void)
               "\n"
               "h();\n");
 
-  jerry_value_t result = run ("capture_test.js", source_p);
+  jerry_value_t result = run (jerry_sz_ascii ("capture_test.js"), source_p);
 
   TEST_ASSERT (jerry_value_is_undefined (result));
   jerry_value_free (result);
@@ -401,7 +400,7 @@ test_get_backtrace_api_call (void)
                 "\n"
                 "g();\n");
 
-    result = run ("async_capture_test.js", source_p);
+    result = run (jerry_sz_ascii ("async_capture_test.js"), source_p);
 
     TEST_ASSERT (jerry_value_is_promise (result));
     jerry_value_free (result);
@@ -435,7 +434,7 @@ test_get_backtrace_api_call (void)
                 "}\n"
                 "new C;\n");
 
-    result = run ("class_capture_test.js", source_p);
+    result = run (jerry_sz_ascii ("class_capture_test.js"), source_p);
 
     TEST_ASSERT (!jerry_value_is_exception (result));
     TEST_ASSERT (frame_index == 2);
@@ -447,7 +446,7 @@ test_get_backtrace_api_call (void)
 
   jerry_value_free (result);
 
-  register_callback (global_capture_handler, "global_capture");
+  register_callback (global_capture_handler, jerry_sz_ascii ("global_capture"));
 
   frame_index = 0;
 
@@ -483,7 +482,7 @@ test_exception_backtrace (void)
                         "\n"
                         "g();\n");
 
-  jerry_value_t error = run ("bad.js", source);
+  jerry_value_t error = run (jerry_sz_ascii ("bad.js"), source);
 
   TEST_ASSERT (jerry_value_is_exception (error));
 
@@ -491,7 +490,7 @@ test_exception_backtrace (void)
 
   TEST_ASSERT (jerry_value_is_object (error));
 
-  jerry_value_t name = jerry_string_sz ("stack");
+  jerry_value_t name = jerry_sz_ascii ("stack");
   jerry_value_t backtrace = jerry_object_get (error, name);
 
   jerry_value_free (name);
@@ -529,7 +528,7 @@ test_large_line_count (void)
                         "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n"
                         "g();\n");
 
-  jerry_value_t error = run ("bad.js", source);
+  jerry_value_t error = run (jerry_sz_ascii ("bad.js"), source);
 
   TEST_ASSERT (jerry_value_is_exception (error));
 
@@ -537,7 +536,7 @@ test_large_line_count (void)
 
   TEST_ASSERT (jerry_value_is_object (error));
 
-  jerry_value_t name = jerry_string_sz ("stack");
+  jerry_value_t name = jerry_sz_ascii ("stack");
   jerry_value_t backtrace = jerry_object_get (error, name);
 
   jerry_value_free (name);
diff --git a/tests/unit-core/test-bigint.c b/tests/unit-core/test-bigint.c
index 640da0bd95..d23f95deb3 100644
--- a/tests/unit-core/test-bigint.c
+++ b/tests/unit-core/test-bigint.c
@@ -28,7 +28,7 @@ main (void)
 
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t string = jerry_string_sz ("0xfffffff1fffffff2fffffff3");
+  jerry_value_t string = jerry_sz_ascii ("0xfffffff1fffffff2fffffff3");
   TEST_ASSERT (!jerry_value_is_exception (string));
 
   jerry_value_t bigint = jerry_value_to_bigint (string);
diff --git a/tests/unit-core/test-common.h b/tests/unit-core/test-common.h
index b6d83491c5..b34166d96c 100644
--- a/tests/unit-core/test-common.h
+++ b/tests/unit-core/test-common.h
@@ -25,8 +25,6 @@
 
 #include "jerryscript-port.h"
 
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define TEST_ASSERT(x)                                           \
   do                                                             \
   {                                                              \
diff --git a/tests/unit-core/test-container-operation.c b/tests/unit-core/test-container-operation.c
index a641ea91a6..4e5e69894a 100644
--- a/tests/unit-core/test-container-operation.c
+++ b/tests/unit-core/test-container-operation.c
@@ -34,7 +34,7 @@ main (void)
   jerry_value_t map = jerry_container (JERRY_CONTAINER_TYPE_MAP, NULL, 0);
   TEST_ASSERT (jerry_container_type (map) == JERRY_CONTAINER_TYPE_MAP);
 
-  jerry_value_t key_str = jerry_string_sz ("number");
+  jerry_value_t key_str = jerry_sz_ascii ("number");
   jerry_value_t number = jerry_number (10);
   jerry_value_t args[2] = { key_str, number };
   jerry_value_t result = jerry_container_op (JERRY_CONTAINER_OP_SET, map, args, 2);
@@ -53,7 +53,7 @@ main (void)
   TEST_ASSERT (jerry_value_as_number (result) == 1);
   jerry_value_free (result);
 
-  key_str = jerry_string_sz ("number2");
+  key_str = jerry_sz_ascii ("number2");
   number = jerry_number (11);
   jerry_value_t args2[2] = { key_str, number };
   result = jerry_container_op (JERRY_CONTAINER_OP_SET, map, args2, 2);
@@ -164,8 +164,7 @@ main (void)
   jerry_value_free (result);
 
   // arguments is a error
-  const char *const error_message_p = "Random error.";
-  jerry_value_t error_val = jerry_throw_sz (JERRY_ERROR_RANGE, error_message_p);
+  jerry_value_t error_val = jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii ("Random error."));
   jerry_value_t args3[2] = { error_val, error_val };
   result = jerry_container_op (JERRY_CONTAINER_OP_SET, map, args3, 2);
   TEST_ASSERT (jerry_value_is_exception (result));
diff --git a/tests/unit-core/test-container.c b/tests/unit-core/test-container.c
index 389a8a6b7b..86d0c3caec 100644
--- a/tests/unit-core/test-container.c
+++ b/tests/unit-core/test-container.c
@@ -84,17 +84,17 @@ main (void)
 
   jerry_value_t instance_check;
   jerry_value_t global = jerry_current_realm ();
-  jerry_value_t map_str = jerry_string_sz ("Map");
-  jerry_value_t set_str = jerry_string_sz ("Set");
-  jerry_value_t weakmap_str = jerry_string_sz ("WeakMap");
-  jerry_value_t weakset_str = jerry_string_sz ("WeakSet");
+  jerry_value_t map_str = jerry_sz_ascii ("Map");
+  jerry_value_t set_str = jerry_sz_ascii ("Set");
+  jerry_value_t weakmap_str = jerry_sz_ascii ("WeakMap");
+  jerry_value_t weakset_str = jerry_sz_ascii ("WeakSet");
   jerry_value_t global_map = jerry_object_get (global, map_str);
   jerry_value_t global_set = jerry_object_get (global, set_str);
   jerry_value_t global_weakmap = jerry_object_get (global, weakmap_str);
   jerry_value_t global_weakset = jerry_object_get (global, weakset_str);
 
   jerry_value_t function = jerry_function_external (create_array_from_container_handler);
-  jerry_value_t name = jerry_string_sz ("create_array_from_container");
+  jerry_value_t name = jerry_sz_ascii ("create_array_from_container");
   jerry_value_t res = jerry_object_set (global, name, function);
   TEST_ASSERT (!jerry_value_is_exception (res));
 
diff --git a/tests/unit-core/test-dataview.c b/tests/unit-core/test-dataview.c
index d392bb799f..05f4767c49 100644
--- a/tests/unit-core/test-dataview.c
+++ b/tests/unit-core/test-dataview.c
@@ -73,8 +73,8 @@ main (void)
 
   /* Test getting/setting values */
   jerry_value_t global_obj = jerry_current_realm ();
-  jerry_value_t view1_str = jerry_string_sz ("view1");
-  jerry_value_t view2_str = jerry_string_sz ("view2");
+  jerry_value_t view1_str = jerry_sz_ascii ("view1");
+  jerry_value_t view2_str = jerry_sz_ascii ("view2");
   TEST_ASSERT (jerry_object_set (global_obj, view1_str, view1));
   TEST_ASSERT (jerry_object_set (global_obj, view2_str, view2));
 
diff --git a/tests/unit-core/test-error-callback.c b/tests/unit-core/test-error-callback.c
index 3fe32d92d9..b9cdcb7a8c 100644
--- a/tests/unit-core/test-error-callback.c
+++ b/tests/unit-core/test-error-callback.c
@@ -30,8 +30,8 @@ error_object_created_callback (const jerry_value_t error_object_t, /**< new erro
   error_object_created_callback_is_running = true;
   error_object_created_callback_count++;
 
-  jerry_value_t name = jerry_string_sz ("message");
-  jerry_value_t message = jerry_string_sz ("Replaced message!");
+  jerry_value_t name = jerry_sz_ascii ("message");
+  jerry_value_t message = jerry_sz_ascii ("Replaced message!");
 
   jerry_value_t result = jerry_object_set (error_object_t, name, message);
   TEST_ASSERT (jerry_value_is_boolean (result) && jerry_value_is_true (result));
@@ -84,7 +84,7 @@ main (void)
   run_test ("var error = new Error()\n"
             "error.message === 'Replaced message!'\n");
 
-  jerry_value_free (jerry_error_sz (JERRY_ERROR_COMMON, "Message"));
+  jerry_value_free (jerry_error_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Message")));
 
   TEST_ASSERT (error_object_created_callback_count == 11);
 
diff --git a/tests/unit-core/test-external-string.c b/tests/unit-core/test-external-string.c
index 3de28ebfb8..1a9cacfd3e 100644
--- a/tests/unit-core/test-external-string.c
+++ b/tests/unit-core/test-external-string.c
@@ -19,17 +19,17 @@
 
 static int free_count = 0;
 
-static const char *external_1 = "External string! External string! External string! External string!";
-static const char *external_2 = "Object";
-static const char *external_3 = "x!?:s";
-static const char *external_4 = "Object property external string! Object property external string!";
+#define external_1 "External string! External string! External string! External string!"
+#define external_2 "Object"
+#define external_3 "x!?:s"
+#define external_4 "Object property external string! Object property external string!"
 
 static void
 external_string_free_callback_1 (jerry_char_t *string_p, /**< string pointer */
                                  jerry_size_t string_size, /**< size of the string */
                                  void *user_p) /**< user pointer */
 {
-  TEST_ASSERT ((const char *) string_p == external_1);
+  TEST_ASSERT (strcmp ((char *) string_p, external_1) == 0);
   TEST_ASSERT (string_size == strlen (external_1));
   TEST_ASSERT (user_p == NULL);
   free_count++;
@@ -40,7 +40,7 @@ external_string_free_callback_2 (jerry_char_t *string_p, /**< string pointer */
                                  jerry_size_t string_size, /**< size of the string */
                                  void *user_p) /**< user pointer */
 {
-  TEST_ASSERT ((const char *) string_p == external_2);
+  TEST_ASSERT (strcmp ((char *) string_p, external_2) == 0);
   TEST_ASSERT (string_size == strlen (external_2));
   TEST_ASSERT (user_p == (void *) &free_count);
   free_count++;
@@ -51,7 +51,7 @@ external_string_free_callback_3 (jerry_char_t *string_p, /**< string pointer */
                                  jerry_size_t string_size, /**< size of the string */
                                  void *user_p) /**< user pointer */
 {
-  TEST_ASSERT ((const char *) string_p == external_3);
+  TEST_ASSERT (strcmp ((char *) string_p, external_3) == 0);
   TEST_ASSERT (string_size == strlen (external_3));
   TEST_ASSERT (user_p == (void *) string_p);
   free_count++;
@@ -68,7 +68,7 @@ main (void)
 
   /* Test external callback calls. */
   jerry_string_external_on_free (external_string_free_callback_1);
-  jerry_value_t external_string = jerry_string_external_sz (external_1, NULL);
+  jerry_value_t external_string = jerry_string_external (JERRY_ZSTR_ARG (external_1), NULL);
   TEST_ASSERT (free_count == 0);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == NULL);
   TEST_ASSERT (is_external);
@@ -77,7 +77,7 @@ main (void)
   TEST_ASSERT (free_count == 1);
 
   jerry_string_external_on_free (NULL);
-  external_string = jerry_string_external_sz (external_1, (void *) &free_count);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_1), (void *) &free_count);
   TEST_ASSERT (free_count == 1);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == (void *) &free_count);
   TEST_ASSERT (is_external);
@@ -86,7 +86,7 @@ main (void)
   TEST_ASSERT (free_count == 1);
 
   jerry_string_external_on_free (external_string_free_callback_2);
-  external_string = jerry_string_external_sz (external_2, (void *) &free_count);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_2), (void *) &free_count);
   TEST_ASSERT (free_count == 2);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == NULL);
   TEST_ASSERT (!is_external);
@@ -94,7 +94,7 @@ main (void)
   TEST_ASSERT (free_count == 2);
 
   jerry_string_external_on_free (NULL);
-  external_string = jerry_string_external_sz (external_2, (void *) &free_count);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_2), (void *) &free_count);
   TEST_ASSERT (free_count == 2);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == NULL);
   TEST_ASSERT (!is_external);
@@ -102,7 +102,8 @@ main (void)
   TEST_ASSERT (free_count == 2);
 
   jerry_string_external_on_free (external_string_free_callback_3);
-  external_string = jerry_string_external_sz (external_3, (void *) external_3);
+  jerry_string_t str = { JERRY_ZSTR_ARG (external_3) };
+  external_string = jerry_string_external (str.ptr, str.size, (void *) str.ptr);
   TEST_ASSERT (free_count == 3);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == NULL);
   TEST_ASSERT (!is_external);
@@ -110,7 +111,7 @@ main (void)
   TEST_ASSERT (free_count == 3);
 
   jerry_string_external_on_free (NULL);
-  external_string = jerry_string_external_sz (external_3, (void *) external_3);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_3), (void *) external_3);
   TEST_ASSERT (free_count == 3);
   TEST_ASSERT (jerry_string_user_ptr (external_string, &is_external) == NULL);
   TEST_ASSERT (!is_external);
@@ -119,8 +120,8 @@ main (void)
 
   /* Test string comparison. */
   jerry_string_external_on_free (external_string_free_callback_1);
-  external_string = jerry_string_external_sz (external_1, NULL);
-  jerry_value_t other_string = jerry_string_sz (external_1);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_1), NULL);
+  jerry_value_t other_string = jerry_sz_ascii (external_1);
 
   jerry_value_t result = jerry_binary_op (JERRY_BIN_OP_STRICT_EQUAL, external_string, other_string);
   TEST_ASSERT (jerry_value_is_boolean (result));
@@ -139,7 +140,7 @@ main (void)
 
   /* Test getting string. */
   jerry_string_external_on_free (external_string_free_callback_1);
-  external_string = jerry_string_external_sz (external_1, NULL);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_1), NULL);
   size_t length = strlen (external_1);
 
   TEST_ASSERT (jerry_value_is_string (external_string));
@@ -156,8 +157,8 @@ main (void)
 
   /* Test property access. */
   jerry_string_external_on_free (NULL);
-  external_string = jerry_string_external_sz (external_4, NULL);
-  other_string = jerry_string_sz (external_4);
+  external_string = jerry_string_external (JERRY_ZSTR_ARG (external_4), NULL);
+  other_string = jerry_sz_ascii (external_4);
 
   jerry_value_t obj = jerry_object ();
   result = jerry_object_set (obj, external_string, other_string);
diff --git a/tests/unit-core/test-from-property-descriptor.c b/tests/unit-core/test-from-property-descriptor.c
index 6134c0c7b4..f3382f3cdf 100644
--- a/tests/unit-core/test-from-property-descriptor.c
+++ b/tests/unit-core/test-from-property-descriptor.c
@@ -26,7 +26,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t object = jerry_object ();
-  jerry_value_t prop_name = jerry_string_sz ("length");
+  jerry_value_t prop_name = jerry_sz_ascii ("length");
   jerry_value_t value = jerry_boolean (true);
 
   TEST_ASSERT (jerry_object_set (object, prop_name, prop_name));
@@ -38,19 +38,19 @@ main (void)
 
   jerry_value_t from_object = jerry_property_descriptor_to_object (&prop_desc);
 
-  prop_name = jerry_string_sz ("value");
+  prop_name = jerry_sz_ascii ("value");
   value = jerry_object_get (from_object, prop_name);
   TEST_ASSERT (value == prop_desc.value);
 
-  prop_name = jerry_string_sz ("writable");
+  prop_name = jerry_sz_ascii ("writable");
   value = jerry_object_get (from_object, prop_name);
   TEST_ASSERT (jerry_value_is_true (value) == ((prop_desc.flags & JERRY_PROP_IS_WRITABLE) != 0));
 
-  prop_name = jerry_string_sz ("enumerable");
+  prop_name = jerry_sz_ascii ("enumerable");
   value = jerry_object_get (from_object, prop_name);
   TEST_ASSERT (jerry_value_is_true (value) == ((prop_desc.flags & JERRY_PROP_IS_ENUMERABLE) != 0));
 
-  prop_name = jerry_string_sz ("configurable");
+  prop_name = jerry_sz_ascii ("configurable");
   value = jerry_object_get (from_object, prop_name);
   TEST_ASSERT (jerry_value_is_true (value) == ((prop_desc.flags & JERRY_PROP_IS_CONFIGURABLE) != 0));
 
diff --git a/tests/unit-core/test-get-own-property.c b/tests/unit-core/test-get-own-property.c
index 4802dffc44..40b08ee524 100644
--- a/tests/unit-core/test-get-own-property.c
+++ b/tests/unit-core/test-get-own-property.c
@@ -47,9 +47,9 @@ main (void)
   TEST_INIT ();
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t pp_string = jerry_string_sz ("pp");
-  jerry_value_t qq_string = jerry_string_sz ("qq");
-  jerry_value_t rr_string = jerry_string_sz ("rr");
+  jerry_value_t pp_string = jerry_sz_ascii ("pp");
+  jerry_value_t qq_string = jerry_sz_ascii ("qq");
+  jerry_value_t rr_string = jerry_sz_ascii ("rr");
 
   jerry_value_t object = create_object ("'use strict';\n"
                                         "({ pp:'A', get qq() { return 'B' } })");
diff --git a/tests/unit-core/test-has-property.c b/tests/unit-core/test-has-property.c
index cb1993b30c..3abd35e4df 100644
--- a/tests/unit-core/test-has-property.c
+++ b/tests/unit-core/test-has-property.c
@@ -34,7 +34,7 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t object = jerry_object ();
-  jerry_value_t prop_name = jerry_string_sz ("something");
+  jerry_value_t prop_name = jerry_sz_ascii ("something");
   jerry_value_t prop_value = jerry_boolean (true);
   jerry_value_t proto_object = jerry_object ();
 
diff --git a/tests/unit-core/test-internal-properties.c b/tests/unit-core/test-internal-properties.c
index 2995a91694..dc1c4f4689 100644
--- a/tests/unit-core/test-internal-properties.c
+++ b/tests/unit-core/test-internal-properties.c
@@ -25,19 +25,19 @@ main (void)
 
   jerry_value_t object = jerry_object ();
 
-  jerry_value_t prop_name_1 = jerry_string_sz ("foo");
-  jerry_value_t prop_name_2 = jerry_string_sz ("non_hidden_prop");
+  jerry_value_t prop_name_1 = jerry_sz_ascii ("foo");
+  jerry_value_t prop_name_2 = jerry_sz_ascii ("non_hidden_prop");
   jerry_value_t prop_name_3;
 
-  jerry_value_t prop_name_3_desc = jerry_string_sz ("bar");
+  jerry_value_t prop_name_3_desc = jerry_sz_ascii ("bar");
   prop_name_3 = jerry_symbol_with_description (prop_name_3_desc);
   jerry_value_free (prop_name_3_desc);
 
-  jerry_value_t internal_prop_name_1 = jerry_string_sz ("hidden_foo");
-  jerry_value_t internal_prop_name_2 = jerry_string_sz ("hidden_prop");
+  jerry_value_t internal_prop_name_1 = jerry_sz_ascii ("hidden_foo");
+  jerry_value_t internal_prop_name_2 = jerry_sz_ascii ("hidden_prop");
   jerry_value_t internal_prop_name_3;
 
-  jerry_value_t internal_prop_name_3_desc = jerry_string_sz ("bar");
+  jerry_value_t internal_prop_name_3_desc = jerry_sz_ascii ("bar");
   internal_prop_name_3 = jerry_symbol_with_description (internal_prop_name_3_desc);
   jerry_value_free (internal_prop_name_3_desc);
 
diff --git a/tests/unit-core/test-is-eval-code.c b/tests/unit-core/test-is-eval-code.c
index 13daa21623..bc159c8387 100644
--- a/tests/unit-core/test-is-eval-code.c
+++ b/tests/unit-core/test-is-eval-code.c
@@ -73,7 +73,7 @@ main (void)
   jerry_value_t global_object_value = jerry_current_realm ();
 
   jerry_value_t function_value = jerry_function_external (check_eval);
-  jerry_value_t function_name_value = jerry_string_sz ("check_eval");
+  jerry_value_t function_name_value = jerry_sz_ascii ("check_eval");
   jerry_value_free (jerry_object_set (global_object_value, function_name_value, function_value));
 
   jerry_value_free (function_name_value);
@@ -94,7 +94,7 @@ main (void)
   }
 
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("");
+  parse_options.argument_list = jerry_sz_ascii ("");
   test_parse (source_p, &parse_options);
   jerry_value_free (parse_options.argument_list);
 
diff --git a/tests/unit-core/test-json.c b/tests/unit-core/test-json.c
index 0d1eef8058..1385187e04 100644
--- a/tests/unit-core/test-json.c
+++ b/tests/unit-core/test-json.c
@@ -27,7 +27,7 @@ custom_to_json (const jerry_call_info_t *call_info_p, /**< call information */
   JERRY_UNUSED (args_p);
   JERRY_UNUSED (args_cnt);
 
-  return jerry_throw_sz (JERRY_ERROR_URI, "Error");
+  return jerry_throw_sz (JERRY_ERROR_URI, jerry_sz_ascii ("Error"));
 } /* custom_to_json */
 
 int
@@ -43,7 +43,7 @@ main (void)
     jerry_value_t parsed_json = jerry_json_parse (data, sizeof (data) - 1);
 
     /* Check "name" property values */
-    jerry_value_t name_key = jerry_string_sz ("name");
+    jerry_value_t name_key = jerry_sz_ascii ("name");
 
     jerry_value_t has_name = jerry_object_has (parsed_json, name_key);
     TEST_ASSERT (jerry_value_is_true (has_name));
@@ -65,7 +65,7 @@ main (void)
     jerry_value_free (name_key);
 
     /* Check "age" property values */
-    jerry_value_t age_key = jerry_string_sz ("age");
+    jerry_value_t age_key = jerry_sz_ascii ("age");
 
     jerry_value_t has_age = jerry_object_has (parsed_json, age_key);
     TEST_ASSERT (jerry_value_is_true (has_age));
@@ -89,7 +89,7 @@ main (void)
     jerry_value_t parsed_cesu8 = jerry_json_parse (cesu8, sizeof (cesu8) - 1);
     jerry_value_t parsed_utf8 = jerry_json_parse (utf8, sizeof (utf8) - 1);
 
-    jerry_value_t key = jerry_string_sz ("ch");
+    jerry_value_t key = jerry_sz_ascii ("ch");
     jerry_value_t char_cesu8 = jerry_object_get (parsed_cesu8, key);
     jerry_value_t char_utf8 = jerry_object_get (parsed_utf8, key);
     jerry_value_free (key);
@@ -121,8 +121,8 @@ main (void)
     jerry_value_t obj = jerry_object ();
     /* Fill "obj" with data */
     {
-      jerry_value_t name_key = jerry_string_sz ("name");
-      jerry_value_t name_value = jerry_string_sz ("John");
+      jerry_value_t name_key = jerry_sz_ascii ("name");
+      jerry_value_t name_value = jerry_sz_ascii ("John");
       jerry_value_t name_set = jerry_object_set (obj, name_key, name_value);
       TEST_ASSERT (!jerry_value_is_exception (name_set));
       TEST_ASSERT (jerry_value_is_boolean (name_set));
@@ -132,7 +132,7 @@ main (void)
       jerry_value_free (name_set);
     }
     {
-      jerry_value_t age_key = jerry_string_sz ("age");
+      jerry_value_t age_key = jerry_sz_ascii ("age");
       jerry_value_t age_value = jerry_number (32);
       jerry_value_t age_set = jerry_object_set (obj, age_key, age_value);
       TEST_ASSERT (!jerry_value_is_exception (age_set));
@@ -165,7 +165,7 @@ main (void)
     jerry_value_t obj = jerry_object ();
     /* Fill "obj" with data */
     {
-      jerry_value_t name_key = jerry_string_sz ("toJSON");
+      jerry_value_t name_key = jerry_sz_ascii ("toJSON");
       jerry_value_t name_value = jerry_function_external (custom_to_json);
       jerry_value_t name_set = jerry_object_set (obj, name_key, name_value);
       TEST_ASSERT (!jerry_value_is_exception (name_set));
diff --git a/tests/unit-core/test-literal-storage.c b/tests/unit-core/test-literal-storage.c
index b52863383b..ecdf594f14 100644
--- a/tests/unit-core/test-literal-storage.c
+++ b/tests/unit-core/test-literal-storage.c
@@ -89,7 +89,7 @@ main (void)
         lit_magic_string_id_t msi = (lit_magic_string_id_t) (rand () % LIT_NON_INTERNAL_MAGIC_STRING__COUNT);
         ptrs[j] = lit_get_magic_string_utf8 (msi);
         TEST_ASSERT (ptrs[j]);
-        lengths[j] = (lit_utf8_size_t) lit_zt_utf8_string_size (ptrs[j]);
+        lengths[j] = lit_get_magic_string_size (msi);
         ecma_find_or_create_literal_string (ptrs[j], lengths[j], false);
       }
       else
diff --git a/tests/unit-core/test-module-dynamic.c b/tests/unit-core/test-module-dynamic.c
index ee99ed3fbf..2d80e42bb1 100644
--- a/tests/unit-core/test-module-dynamic.c
+++ b/tests/unit-core/test-module-dynamic.c
@@ -38,7 +38,7 @@ register_assert (void)
   jerry_value_t global_object_value = jerry_current_realm ();
 
   jerry_value_t function_value = jerry_function_external (global_assert);
-  jerry_value_t function_name_value = jerry_string_sz ("assert");
+  jerry_value_t function_name_value = jerry_sz_ascii ("assert");
   jerry_value_t result_value = jerry_object_set (global_object_value, function_name_value, function_value);
 
   jerry_value_free (function_name_value);
@@ -90,7 +90,7 @@ module_import_callback (const jerry_value_t specifier, /* string value */
     case 0:
     {
       compare_specifier (specifier, 1);
-      return jerry_throw_sz (JERRY_ERROR_RANGE, "Err01");
+      return jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii ("Err01"));
     }
     case 1:
     {
@@ -113,7 +113,7 @@ module_import_callback (const jerry_value_t specifier, /* string value */
       compare_specifier (specifier, 28);
 
       TEST_ASSERT (jerry_value_is_object (user_value));
-      jerry_value_t property_name = jerry_string_sz ("MyProp1");
+      jerry_value_t property_name = jerry_sz_ascii ("MyProp1");
       jerry_value_t result = jerry_object_get (user_value, property_name);
       TEST_ASSERT (jerry_value_is_number (result) && jerry_value_as_number (result) == 3.5);
       jerry_value_free (result);
@@ -259,7 +259,7 @@ main (void)
   run_script (source_p, &parse_options, false);
   jerry_value_free (global_user_value);
 
-  global_user_value = jerry_string_sz ("Any string...");
+  global_user_value = jerry_sz_ascii ("Any string...");
   source_p = TEST_STRING_LITERAL ("var src = \"import('02_module.mjs').then(\\\n"
                                   "  function(resolve) { assert(typeof resolve == 'object') },\\\n"
                                   "  function(reject) { assert(false) }\\\n"
@@ -274,7 +274,7 @@ main (void)
     mode = 3;
     parse_options.options = JERRY_PARSE_HAS_USER_VALUE | (i == 1 ? JERRY_PARSE_MODULE : 0);
     parse_options.user_value = jerry_object ();
-    jerry_value_t property_name = jerry_string_sz ("MyProp1");
+    jerry_value_t property_name = jerry_sz_ascii ("MyProp1");
     jerry_value_t property_value = jerry_number (3.5);
     jerry_value_t result = jerry_object_set (parse_options.user_value, property_name, property_value);
     TEST_ASSERT (jerry_value_is_true (result));
diff --git a/tests/unit-core/test-module-import-meta.c b/tests/unit-core/test-module-import-meta.c
index 9adaab0339..957152b00a 100644
--- a/tests/unit-core/test-module-import-meta.c
+++ b/tests/unit-core/test-module-import-meta.c
@@ -38,7 +38,7 @@ register_assert (void)
   jerry_value_t global_object_value = jerry_current_realm ();
 
   jerry_value_t function_value = jerry_function_external (global_assert);
-  jerry_value_t function_name_value = jerry_string_sz ("assert");
+  jerry_value_t function_name_value = jerry_sz_ascii ("assert");
   jerry_value_t result_value = jerry_object_set (global_object_value, function_name_value, function_value);
 
   jerry_value_free (function_name_value);
@@ -57,7 +57,7 @@ module_import_meta_callback (const jerry_value_t module, /**< module */
   TEST_ASSERT (user_p == (void *) &counter);
   TEST_ASSERT (module == global_module_value);
 
-  jerry_value_t property_name_value = jerry_string_sz ("prop");
+  jerry_value_t property_name_value = jerry_sz_ascii ("prop");
   jerry_value_t result_value = jerry_object_set (meta_object, property_name_value, property_name_value);
   jerry_value_free (result_value);
   jerry_value_free (property_name_value);
diff --git a/tests/unit-core/test-module.c b/tests/unit-core/test-module.c
index cd01dd45ef..c700d3a1e0 100644
--- a/tests/unit-core/test-module.c
+++ b/tests/unit-core/test-module.c
@@ -42,10 +42,9 @@ compare_specifier (jerry_value_t specifier, /* string value */
 
 static void
 compare_property (jerry_value_t namespace_object, /**< namespace object */
-                  const char *name_p, /**< property name */
+                  jerry_value_t name, /**< property name that will be free/take*/
                   double expected_value) /**< property value (number for simplicity) */
 {
-  jerry_value_t name = jerry_string_sz (name_p);
   jerry_value_t result = jerry_object_get (namespace_object, name);
 
   TEST_ASSERT (jerry_value_is_number (result));
@@ -118,7 +117,7 @@ resolve_callback2 (const jerry_value_t specifier, /**< module specifier */
   {
     if (terminate_with_error)
     {
-      return jerry_throw_sz (JERRY_ERROR_RANGE, "Module not found");
+      return jerry_throw_sz (JERRY_ERROR_RANGE, jerry_sz_ascii ("Module not found"));
     }
 
     return create_module (0);
@@ -147,10 +146,10 @@ native_module_evaluate (const jerry_value_t native_module) /**< native module */
 
   TEST_ASSERT (jerry_module_state (module) == JERRY_MODULE_STATE_EVALUATING);
 
-  jerry_value_t exp_val = jerry_string_sz ("exp");
-  jerry_value_t other_exp_val = jerry_string_sz ("other_exp");
+  jerry_value_t exp_val = jerry_sz_ascii ("exp");
+  jerry_value_t other_exp_val = jerry_sz_ascii ("other_exp");
   /* The native module has no such export. */
-  jerry_value_t no_exp_val = jerry_string_sz ("no_exp");
+  jerry_value_t no_exp_val = jerry_sz_ascii ("no_exp");
 
   jerry_value_t result = jerry_native_module_get (native_module, exp_val);
   TEST_ASSERT (jerry_value_is_undefined (result));
@@ -171,7 +170,7 @@ native_module_evaluate (const jerry_value_t native_module) /**< native module */
   jerry_value_free (result);
   jerry_value_free (export);
 
-  export = jerry_string_sz ("str");
+  export = jerry_sz_ascii ("str");
   result = jerry_native_module_set (native_module, other_exp_val, export);
   TEST_ASSERT (jerry_value_is_boolean (result) && jerry_value_is_true (result));
   jerry_value_free (result);
@@ -197,7 +196,7 @@ native_module_evaluate (const jerry_value_t native_module) /**< native module */
   if (counter == 4)
   {
     ++counter;
-    return jerry_throw_sz (JERRY_ERROR_COMMON, "Ooops!");
+    return jerry_throw_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Ooops!"));
   }
 
   return jerry_undefined ();
@@ -213,7 +212,7 @@ resolve_callback4 (const jerry_value_t specifier, /**< module specifier */
 
   ++counter;
 
-  jerry_value_t exports[2] = { jerry_string_sz ("exp"), jerry_string_sz ("other_exp") };
+  jerry_value_t exports[2] = { jerry_sz_ascii ("exp"), jerry_sz_ascii ("other_exp") };
 
   jerry_value_t native_module = jerry_native_module (native_module_evaluate, exports, 2);
   TEST_ASSERT (!jerry_value_is_exception (native_module));
@@ -414,8 +413,8 @@ main (void)
 
   result = jerry_module_namespace (module);
   TEST_ASSERT (jerry_value_is_object (result));
-  compare_property (result, "a", 6);
-  compare_property (result, "b", 8.5);
+  compare_property (result, jerry_sz_ascii ("a"), 6);
+  compare_property (result, jerry_sz_ascii ("b"), 8.5);
   jerry_value_free (result);
 
   jerry_value_free (module);
@@ -439,7 +438,7 @@ main (void)
   jerry_value_free (module);
 
   /* Valid identifier. */
-  jerry_value_t export = jerry_string_sz ("\xed\xa0\x83\xed\xb2\x80");
+  jerry_value_t export = jerry_sz_cesu8 ("\xed\xa0\x83\xed\xb2\x80");
 
   module = jerry_native_module (NULL, &export, 1);
   TEST_ASSERT (!jerry_value_is_exception (module));
@@ -457,13 +456,13 @@ main (void)
   jerry_value_free (export);
 
   /* Invalid identifiers. */
-  export = jerry_string_sz ("a+");
+  export = jerry_sz_ascii ("a+");
   module = jerry_native_module (NULL, &export, 1);
   TEST_ASSERT (jerry_value_is_exception (module));
   jerry_value_free (module);
   jerry_value_free (export);
 
-  export = jerry_string_sz ("\xed\xa0\x80");
+  export = jerry_sz_cesu8 ("\xed\xa0\x80");
   module = jerry_native_module (NULL, &export, 1);
   TEST_ASSERT (jerry_value_is_exception (module));
   jerry_value_free (module);
diff --git a/tests/unit-core/test-native-instanceof.c b/tests/unit-core/test-native-instanceof.c
index e5fcad0655..fbd2290e6c 100644
--- a/tests/unit-core/test-native-instanceof.c
+++ b/tests/unit-core/test-native-instanceof.c
@@ -63,7 +63,7 @@ main (void)
 
   /* Test for a JS constructor. */
   jerry_value_t global = jerry_current_realm ();
-  jerry_value_t object_name = jerry_string_sz ("Object");
+  jerry_value_t object_name = jerry_sz_ascii ("Object");
   constructor = jerry_object_get (global, object_name);
   jerry_value_free (object_name);
   jerry_value_free (global);
diff --git a/tests/unit-core/test-native-pointer.c b/tests/unit-core/test-native-pointer.c
index 664aba4616..937b16075e 100644
--- a/tests/unit-core/test-native-pointer.c
+++ b/tests/unit-core/test-native-pointer.c
@@ -233,8 +233,8 @@ main (void)
   TEST_ASSERT (!jerry_object_has_native_ptr (object_value, &native_info_3));
 
   /* Test value references */
-  jerry_value_t string1_value = jerry_string_sz ("String1");
-  jerry_value_t string2_value = jerry_string_sz ("String2");
+  jerry_value_t string1_value = jerry_sz_ascii ("String1");
+  jerry_value_t string2_value = jerry_sz_ascii ("String2");
 
   jerry_value_t object1_value = jerry_object ();
   jerry_value_t object2_value = jerry_object ();
diff --git a/tests/unit-core/test-newtarget.c b/tests/unit-core/test-newtarget.c
index d5b28240fe..38fc577bb9 100644
--- a/tests/unit-core/test-newtarget.c
+++ b/tests/unit-core/test-newtarget.c
@@ -22,13 +22,12 @@
  * Register a JavaScript function in the global object.
  */
 static jerry_value_t
-register_js_function (const char *name_p, /**< name of the function */
+register_js_function (jerry_value_t function_name_val, /**< name of the function that will be free/take */
                       jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
   jerry_value_t function_val = jerry_function_external (handler_p);
-  jerry_value_t function_name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (global_obj_val, function_name_val, function_val);
 
   jerry_value_free (function_name_val);
@@ -110,7 +109,7 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t demo_func = register_js_function ("Demo", construct_handler);
+  jerry_value_t demo_func = register_js_function (jerry_sz_ascii ("Demo"), construct_handler);
 
   {
     jerry_value_t test_arg = jerry_number (TEST_ID_SIMPLE_CONSTRUCT);
diff --git a/tests/unit-core/test-number-converter.c b/tests/unit-core/test-number-converter.c
index 9b7116cb27..d827ac70f9 100644
--- a/tests/unit-core/test-number-converter.c
+++ b/tests/unit-core/test-number-converter.c
@@ -115,7 +115,7 @@ main (void)
   test_to_interger (-4294967297, -4294967297);
 
   // few test-cases which return with error
-  jerry_value_t error_val = jerry_throw_sz (JERRY_ERROR_TYPE, "error");
+  jerry_value_t error_val = jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error"));
   double number = jerry_value_as_integer (error_val);
   jerry_value_free (error_val);
   TEST_ASSERT (number == 0);
diff --git a/tests/unit-core/test-objects-foreach.c b/tests/unit-core/test-objects-foreach.c
index d97cfe6da2..701a5adbd0 100644
--- a/tests/unit-core/test-objects-foreach.c
+++ b/tests/unit-core/test-objects-foreach.c
@@ -33,7 +33,7 @@ static void
 test_container (void)
 {
   jerry_value_t global = jerry_current_realm ();
-  jerry_value_t map_str = jerry_string_sz ("Map");
+  jerry_value_t map_str = jerry_sz_ascii ("Map");
   jerry_value_t map_result = jerry_object_get (global, map_str);
   jerry_type_t type = jerry_value_type (map_result);
 
@@ -111,7 +111,7 @@ test_internal_prop (void)
     TEST_ASSERT ((after_object_count - before_object_count) == 1);
   }
 
-  jerry_value_t internal_prop_name = jerry_string_sz ("hidden_foo");
+  jerry_value_t internal_prop_name = jerry_sz_ascii ("hidden_foo");
   jerry_value_t internal_prop_object = jerry_object ();
   bool internal_result = jerry_object_set_internal (object, internal_prop_name, internal_prop_object);
   TEST_ASSERT (internal_result == true);
@@ -221,7 +221,7 @@ main (void)
 
   /* Create an object and set a property on it. */
   object = jerry_object ();
-  jerry_value_t property_name = jerry_string_sz ("xyzzy");
+  jerry_value_t property_name = jerry_sz_ascii ("xyzzy");
   jerry_value_t property_value = jerry_number (42);
   jerry_value_free (jerry_object_set (object, property_name, property_value));
   jerry_value_free (property_value);
diff --git a/tests/unit-core/test-promise.c b/tests/unit-core/test-promise.c
index b66ce791c3..c1b5ae5546 100644
--- a/tests/unit-core/test-promise.c
+++ b/tests/unit-core/test-promise.c
@@ -30,8 +30,8 @@ static const jerry_char_t test_source[] = TEST_STRING_LITERAL ("var p1 = create_
 static int count_in_assert = 0;
 static jerry_value_t my_promise1;
 static jerry_value_t my_promise2;
-static const char s1[] = "resolved";
-static const char s2[] = "rejected";
+#define s1 "resolved"
+#define s2 "rejected"
 
 static jerry_value_t
 create_promise1_handler (const jerry_call_info_t *call_info_p, /**< call information */
@@ -86,13 +86,12 @@ assert_handler (const jerry_call_info_t *call_info_p, /**< call information */
  * Register a JavaScript function in the global object.
  */
 static void
-register_js_function (const char *name_p, /**< name of the function */
+register_js_function (jerry_value_t function_name_val, /**< name of the function that will be free/take*/
                       jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
   jerry_value_t function_val = jerry_function_external (handler_p);
-  jerry_value_t function_name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (global_obj_val, function_name_val, function_val);
 
   jerry_value_free (function_name_val);
@@ -107,9 +106,9 @@ main (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  register_js_function ("create_promise1", create_promise1_handler);
-  register_js_function ("create_promise2", create_promise2_handler);
-  register_js_function ("assert", assert_handler);
+  register_js_function (jerry_sz_ascii ("create_promise1"), create_promise1_handler);
+  register_js_function (jerry_sz_ascii ("create_promise2"), create_promise2_handler);
+  register_js_function (jerry_sz_ascii ("assert"), assert_handler);
 
   jerry_value_t parsed_code_val = jerry_parse (test_source, sizeof (test_source) - 1, NULL);
   TEST_ASSERT (!jerry_value_is_exception (parsed_code_val));
@@ -127,8 +126,8 @@ main (void)
   TEST_ASSERT (count_in_assert == 0);
 
   /* Test jerry_resolve_or_reject_promise. */
-  jerry_value_t str_resolve = jerry_string_sz (s1);
-  jerry_value_t str_reject = jerry_string_sz (s2);
+  jerry_value_t str_resolve = jerry_sz_ascii (s1);
+  jerry_value_t str_reject = jerry_sz_ascii (s2);
 
   jerry_promise_resolve (my_promise1, str_resolve);
   jerry_promise_reject (my_promise2, str_reject);
diff --git a/tests/unit-core/test-proxy.c b/tests/unit-core/test-proxy.c
index 40c70e53ea..6a015a1d90 100644
--- a/tests/unit-core/test-proxy.c
+++ b/tests/unit-core/test-proxy.c
@@ -111,10 +111,9 @@ handler_set (const jerry_call_info_t *call_info_p, /**< call information */
 
 static void
 set_property (jerry_value_t target, /**< target object */
-              const char *name_p, /**< name of the property */
+              jerry_value_t name_val, /**< name of the property that will be free/take */
               jerry_value_t value) /**< value of the property */
 {
-  jerry_value_t name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (target, name_val, value);
 
   TEST_ASSERT (jerry_value_is_boolean (result_val));
@@ -124,9 +123,8 @@ set_property (jerry_value_t target, /**< target object */
 
 static jerry_value_t
 get_property (jerry_value_t target, /**< target object */
-              const char *name_p) /**< name of the property */
+              jerry_value_t name_val) /**< name of the property that will be free/take */
 {
-  jerry_value_t name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_get (target, name_val);
 
   TEST_ASSERT (!jerry_value_is_exception (result_val));
@@ -136,11 +134,11 @@ get_property (jerry_value_t target, /**< target object */
 
 static void
 set_function (jerry_value_t target, /**< target object */
-              const char *name_p, /**< name of the function */
+              jerry_value_t name_val, /**< name of the function that will be free/take */
               jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t function_val = jerry_function_external (handler_p);
-  set_property (target, name_p, function_val);
+  set_property (target, name_val, function_val);
   jerry_value_free (function_val);
 } /* set_function */
 
@@ -193,7 +191,7 @@ static void
 test_proxy_native (void)
 {
   jerry_value_t handler = jerry_object ();
-  set_function (handler, "get", proxy_native_handler_get);
+  set_function (handler, jerry_sz_ascii ("get"), proxy_native_handler_get);
 
   jerry_value_t target = jerry_object ();
   jerry_value_t proxy = jerry_proxy (target, handler);
@@ -233,15 +231,15 @@ main (void)
 
   jerry_value_t handler = jerry_object ();
   {
-    set_function (handler, "get", handler_get);
-    set_function (handler, "set", handler_set);
+    set_function (handler, jerry_sz_ascii ("get"), handler_get);
+    set_function (handler, jerry_sz_ascii ("set"), handler_set);
   }
 
   jerry_value_t target = jerry_object ();
   jerry_value_t proxy = jerry_proxy (target, handler);
   {
     jerry_value_t global = jerry_current_realm ();
-    set_property (global, "pdemo", proxy);
+    set_property (global, jerry_sz_ascii ("pdemo"), proxy);
     jerry_value_free (global);
   }
 
@@ -257,7 +255,7 @@ main (void)
   }
 
   {
-    jerry_value_t res = get_property (proxy, "value");
+    jerry_value_t res = get_property (proxy, jerry_sz_ascii ("value"));
     TEST_ASSERT (jerry_value_is_number (res));
     TEST_ASSERT (jerry_value_as_number (res) == 2.0);
     jerry_value_free (res);
@@ -290,12 +288,12 @@ main (void)
 
   {
     jerry_value_t new_value = jerry_number (12);
-    set_property (proxy, "value", new_value);
+    set_property (proxy, jerry_sz_ascii ("value"), new_value);
     jerry_value_free (new_value);
   }
 
   {
-    jerry_value_t res = get_property (proxy, "value");
+    jerry_value_t res = get_property (proxy, jerry_sz_ascii ("value"));
     TEST_ASSERT (jerry_value_is_number (res));
     TEST_ASSERT (jerry_value_as_number (res) == 13.0);
     jerry_value_free (res);
@@ -318,7 +316,7 @@ main (void)
     jerry_value_free (parsed_has_code_val);
     TEST_ASSERT (jerry_value_is_proxy (res));
 
-    jerry_value_t name = jerry_string_sz ("key");
+    jerry_value_t name = jerry_sz_ascii ("key");
     TEST_ASSERT (jerry_value_is_string (name));
     jerry_value_t property = jerry_object_has (res, name);
     jerry_value_free (name);
diff --git a/tests/unit-core/test-realm.c b/tests/unit-core/test-realm.c
index db088fd5b0..58b39acd39 100644
--- a/tests/unit-core/test-realm.c
+++ b/tests/unit-core/test-realm.c
@@ -19,10 +19,9 @@
 
 static void
 create_number_property (jerry_value_t object_value, /**< object value */
-                        char *name_p, /**< name */
+                        jerry_value_t name_value, /**< name that will be take/free*/
                         double number) /**< value */
 {
-  jerry_value_t name_value = jerry_string_sz (name_p);
   jerry_value_t number_value = jerry_number (number);
   jerry_value_t result_value = jerry_object_set (object_value, name_value, number_value);
   TEST_ASSERT (!jerry_value_is_exception (result_value));
@@ -34,9 +33,8 @@ create_number_property (jerry_value_t object_value, /**< object value */
 
 static double
 get_number_property (jerry_value_t object_value, /**< object value */
-                     char *name_p) /**< name */
+                     jerry_value_t name_value) /**< name that will be free/take */
 {
-  jerry_value_t name_value = jerry_string_sz (name_p);
   jerry_value_t result_value = jerry_object_get (object_value, name_value);
   TEST_ASSERT (!jerry_value_is_exception (result_value));
   TEST_ASSERT (jerry_value_is_number (result_value));
@@ -72,12 +70,12 @@ check_type_error (jerry_value_t result_value) /**< result value */
 static void
 check_array_prototype (jerry_value_t realm_value, jerry_value_t result_value)
 {
-  jerry_value_t name_value = jerry_string_sz ("Array");
+  jerry_value_t name_value = jerry_sz_ascii ("Array");
   jerry_value_t array_value = jerry_object_get (realm_value, name_value);
   TEST_ASSERT (jerry_value_is_object (array_value));
   jerry_value_free (name_value);
 
-  name_value = jerry_string_sz ("prototype");
+  name_value = jerry_sz_ascii ("prototype");
   jerry_value_t prototype_value = jerry_object_get (array_value, name_value);
   TEST_ASSERT (jerry_value_is_object (prototype_value));
   jerry_value_free (name_value);
@@ -117,10 +115,10 @@ main (void)
 
   jerry_value_t realm_value = jerry_realm ();
 
-  create_number_property (global_value, "a", 3.5);
-  create_number_property (global_value, "b", 7.25);
-  create_number_property (realm_value, "a", -1.25);
-  create_number_property (realm_value, "b", -6.75);
+  create_number_property (global_value, jerry_sz_ascii ("a"), 3.5);
+  create_number_property (global_value, jerry_sz_ascii ("b"), 7.25);
+  create_number_property (realm_value, jerry_sz_ascii ("a"), -1.25);
+  create_number_property (realm_value, jerry_sz_ascii ("b"), -6.75);
 
   TEST_ASSERT (eval_and_get_number ("a") == 3.5);
 
@@ -170,15 +168,15 @@ main (void)
   TEST_ASSERT (jerry_value_is_boolean (result_value) && jerry_value_is_true (result_value));
   jerry_value_free (result_value);
 
-  create_number_property (object_value, "x", 7.25);
-  create_number_property (object_value, "y", 1.25);
+  create_number_property (object_value, jerry_sz_ascii ("x"), 7.25);
+  create_number_property (object_value, jerry_sz_ascii ("y"), 1.25);
 
   result_value = jerry_set_realm (realm_value);
   TEST_ASSERT (!jerry_value_is_exception (result_value));
   TEST_ASSERT (eval_and_get_number ("var z = -5.5; x + this.y") == 8.5);
   jerry_set_realm (result_value);
 
-  TEST_ASSERT (get_number_property (object_value, "z") == -5.5);
+  TEST_ASSERT (get_number_property (object_value, jerry_sz_ascii ("z")) == -5.5);
 
   result_value = jerry_realm_this (realm_value);
   TEST_ASSERT (result_value == object_value);
@@ -203,7 +201,7 @@ main (void)
     TEST_ASSERT (eval_and_get_number ("var z = 1.5; z") == 1.5);
     jerry_set_realm (old_realm_value);
 
-    TEST_ASSERT (get_number_property (target_value, "z") == 1.5);
+    TEST_ASSERT (get_number_property (target_value, jerry_sz_ascii ("z")) == 1.5);
     jerry_value_free (target_value);
 
     /* Check isExtensible error. */
@@ -241,7 +239,7 @@ main (void)
   jerry_set_realm (result_value);
 
   /* Script is compiled in another realm. */
-  create_number_property (realm_value, "global1", 7.5);
+  create_number_property (realm_value, jerry_sz_ascii ("global1"), 7.5);
   result_value = jerry_run (script_value);
   TEST_ASSERT (!jerry_value_is_exception (result_value));
 
@@ -250,7 +248,7 @@ main (void)
   jerry_value_free (result_value);
   jerry_value_free (script_value);
 
-  TEST_ASSERT (get_number_property (realm_value, "global2") == 6.5);
+  TEST_ASSERT (get_number_property (realm_value, jerry_sz_ascii ("global2")) == 6.5);
 
   jerry_value_free (realm_value);
 
diff --git a/tests/unit-core/test-regexp-dotall-unicode.c b/tests/unit-core/test-regexp-dotall-unicode.c
index 64453523ca..0e0ad7022f 100644
--- a/tests/unit-core/test-regexp-dotall-unicode.c
+++ b/tests/unit-core/test-regexp-dotall-unicode.c
@@ -24,17 +24,17 @@ main (void)
   jerry_init (JERRY_INIT_EMPTY);
 
   jerry_value_t undefined_this_arg = jerry_undefined ();
-  char pattern2[] = "\\u{61}.\\u{62}";
+#define pattern2 "\\u{61}.\\u{62}"
 
   uint16_t flags = JERRY_REGEXP_FLAG_DOTALL | JERRY_REGEXP_FLAG_UNICODE | JERRY_REGEXP_FLAG_STICKY;
-  jerry_value_t regex_obj = jerry_regexp_sz (pattern2, flags);
+  jerry_value_t regex_obj = jerry_regexp_sz (jerry_sz_ascii (pattern2), flags);
   TEST_ASSERT (jerry_value_is_object (regex_obj));
 
   const jerry_char_t func_src2[] = "return [regex.exec('a\\nb'), regex.dotAll, regex.sticky, regex.unicode ];";
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("regex");
+  parse_options.argument_list = jerry_sz_ascii ("regex");
 
   jerry_value_t func_val = jerry_parse (func_src2, sizeof (func_src2) - 1, &parse_options);
   jerry_value_free (parse_options.argument_list);
diff --git a/tests/unit-core/test-regexp.c b/tests/unit-core/test-regexp.c
index 8cb4e8251d..8211f97e6d 100644
--- a/tests/unit-core/test-regexp.c
+++ b/tests/unit-core/test-regexp.c
@@ -25,16 +25,16 @@ main (void)
 
   jerry_value_t global_obj_val = jerry_current_realm ();
 
-  char pattern[] = "[^.]+";
+#define pattern "[^.]+"
   uint16_t flags = JERRY_REGEXP_FLAG_GLOBAL | JERRY_REGEXP_FLAG_MULTILINE;
-  jerry_value_t regex_obj = jerry_regexp_sz (pattern, flags);
+  jerry_value_t regex_obj = jerry_regexp_sz (jerry_sz_ascii (pattern), flags);
   TEST_ASSERT (jerry_value_is_object (regex_obj));
 
   const jerry_char_t func_src[] = "return [regex.exec('something.domain.com'), regex.multiline, regex.global];";
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("regex");
+  parse_options.argument_list = jerry_sz_ascii ("regex");
 
   jerry_value_t func_val = jerry_parse (func_src, sizeof (func_src) - 1, &parse_options);
   jerry_value_free (parse_options.argument_list);
diff --git a/tests/unit-core/test-regression-3588.c b/tests/unit-core/test-regression-3588.c
index 87a2dea198..6d63f6931b 100644
--- a/tests/unit-core/test-regression-3588.c
+++ b/tests/unit-core/test-regression-3588.c
@@ -43,7 +43,7 @@ main (void)
     jerry_value_t global_obj_val = jerry_current_realm ();
 
     jerry_value_t function_val = jerry_function_external (construct_handler);
-    jerry_value_t function_name_val = jerry_string_sz ("Demo");
+    jerry_value_t function_name_val = jerry_sz_ascii ("Demo");
     jerry_value_t result_val = jerry_object_set (global_obj_val, function_name_val, function_val);
     TEST_ASSERT (!jerry_value_is_exception (result_val));
     TEST_ASSERT (jerry_value_is_true (result_val));
diff --git a/tests/unit-core/test-script-user-value.c b/tests/unit-core/test-script-user-value.c
index 8effb6ecaa..c0f6aca400 100644
--- a/tests/unit-core/test-script-user-value.c
+++ b/tests/unit-core/test-script-user-value.c
@@ -59,7 +59,7 @@ test_parse_function (const char *source_p, /**< source code */
                      bool run_code) /**< run the code after parsing */
 {
   options_p->options |= JERRY_PARSE_HAS_ARGUMENT_LIST;
-  options_p->argument_list = jerry_string_sz ("");
+  options_p->argument_list = jerry_sz_ascii ("");
 
   for (size_t i = 0; i < USER_VALUES_SIZE; i++)
   {
@@ -101,7 +101,7 @@ main (void)
   user_values[0] = jerry_object ();
   user_values[1] = jerry_null ();
   user_values[2] = jerry_number (5.5);
-  user_values[3] = jerry_string_sz ("AnyString...");
+  user_values[3] = jerry_sz_ascii ("AnyString...");
 
   jerry_parse_options_t parse_options;
   const char *source_p = TEST_STRING_LITERAL ("");
diff --git a/tests/unit-core/test-snapshot.c b/tests/unit-core/test-snapshot.c
index 4de459c1a5..3f792386a4 100644
--- a/tests/unit-core/test-snapshot.c
+++ b/tests/unit-core/test-snapshot.c
@@ -276,7 +276,7 @@ test_function_snapshot (void)
 
   jerry_parse_options_t parse_options;
   parse_options.options = JERRY_PARSE_HAS_ARGUMENT_LIST;
-  parse_options.argument_list = jerry_string_sz ("a, b");
+  parse_options.argument_list = jerry_sz_ascii ("a, b");
 
   jerry_value_t parse_result = jerry_parse (code_to_snapshot, sizeof (code_to_snapshot) - 1, &parse_options);
   TEST_ASSERT (!jerry_value_is_exception (parse_result));
@@ -409,7 +409,7 @@ test_snapshot_with_user (void)
       }
       else
       {
-        snapshot_exec_options.user_value = jerry_string_sz ("AnyString...");
+        snapshot_exec_options.user_value = jerry_sz_ascii ("AnyString...");
       }
 
       jerry_value_t result = jerry_exec_snapshot (snapshot_buffer,
diff --git a/tests/unit-core/test-source-name.c b/tests/unit-core/test-source-name.c
index 9ecd16bdee..4b3807d510 100644
--- a/tests/unit-core/test-source-name.c
+++ b/tests/unit-core/test-source-name.c
@@ -50,7 +50,7 @@ main (void)
   /* Register the "sourceName" method. */
   {
     jerry_value_t func = jerry_function_external (source_name_handler);
-    jerry_value_t name = jerry_string_sz ("sourceName");
+    jerry_value_t name = jerry_sz_ascii ("sourceName");
     jerry_value_t result = jerry_object_set (global, name, func);
     jerry_value_free (result);
     jerry_value_free (name);
@@ -70,7 +70,7 @@ main (void)
                           "} \n"
                           "f1();");
 
-  parse_options.source_name = jerry_string_sz ("demo1.js");
+  parse_options.source_name = jerry_sz_ascii ("demo1.js");
 
   jerry_value_t program = jerry_parse ((const jerry_char_t *) source_1, strlen (source_1), &parse_options);
   TEST_ASSERT (!jerry_value_is_exception (program));
@@ -101,7 +101,7 @@ main (void)
                           "} \n"
                           "f2(); \n");
 
-  parse_options.source_name = jerry_string_sz ("demo2.js");
+  parse_options.source_name = jerry_sz_ascii ("demo2.js");
 
   program = jerry_parse ((const jerry_char_t *) source_2, strlen (source_2), &parse_options);
   TEST_ASSERT (!jerry_value_is_exception (program));
@@ -122,11 +122,11 @@ main (void)
   jerry_value_free (program);
   if (jerry_feature_enabled (JERRY_FEATURE_MODULE))
   {
-    jerry_value_t anon = jerry_string_sz ("<anonymous>");
+    jerry_value_t anon = jerry_sz_ascii ("<anonymous>");
     const char *source_3 = "";
 
     parse_options.options = JERRY_PARSE_MODULE | JERRY_PARSE_HAS_SOURCE_NAME;
-    parse_options.source_name = jerry_string_sz ("demo3.js");
+    parse_options.source_name = jerry_sz_ascii ("demo3.js");
 
     program = jerry_parse ((const jerry_char_t *) source_3, strlen (source_3), &parse_options);
     TEST_ASSERT (!jerry_value_is_exception (program));
@@ -166,7 +166,7 @@ main (void)
                           "f.bind().bind();");
 
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("demo4.js");
+  parse_options.source_name = jerry_sz_ascii ("demo4.js");
 
   program = jerry_parse ((const jerry_char_t *) source_4, strlen (source_4), &parse_options);
   TEST_ASSERT (!jerry_value_is_exception (program));
@@ -189,7 +189,7 @@ main (void)
 
   parse_options.options = JERRY_PARSE_HAS_USER_VALUE | JERRY_PARSE_HAS_SOURCE_NAME;
   parse_options.user_value = jerry_object ();
-  parse_options.source_name = jerry_string_sz ("demo5.js");
+  parse_options.source_name = jerry_sz_ascii ("demo5.js");
 
   program = jerry_parse ((const jerry_char_t *) source_5, strlen (source_5), &parse_options);
   TEST_ASSERT (!jerry_value_is_exception (program));
@@ -207,7 +207,7 @@ main (void)
   const char *source_6 = "(class {})";
 
   parse_options.options = JERRY_PARSE_HAS_SOURCE_NAME;
-  parse_options.source_name = jerry_string_sz ("demo6.js");
+  parse_options.source_name = jerry_sz_ascii ("demo6.js");
 
   program = jerry_parse ((const jerry_char_t *) source_6, strlen (source_6), &parse_options);
   if (!jerry_value_is_exception (program))
diff --git a/tests/unit-core/test-special-proxy.c b/tests/unit-core/test-special-proxy.c
index e7e6e2cd06..233cad2c03 100644
--- a/tests/unit-core/test-special-proxy.c
+++ b/tests/unit-core/test-special-proxy.c
@@ -60,7 +60,7 @@ main (void)
   jerry_value_t global = jerry_current_realm ();
 
   jerry_value_t function = jerry_function_external (create_special_proxy_handler);
-  jerry_value_t name = jerry_string_sz ("create_special_proxy");
+  jerry_value_t name = jerry_sz_ascii ("create_special_proxy");
   jerry_value_t result = jerry_object_set (global, name, function);
   TEST_ASSERT (!jerry_value_is_exception (result));
 
diff --git a/tests/unit-core/test-string-to-number.c b/tests/unit-core/test-string-to-number.c
index 09927534be..b7bdf2e6d1 100644
--- a/tests/unit-core/test-string-to-number.c
+++ b/tests/unit-core/test-string-to-number.c
@@ -27,14 +27,13 @@ int
 main (void)
 {
   TEST_INIT ();
-
-  const jerry_char_t *strings[] = {
-    (const jerry_char_t *) "1",         (const jerry_char_t *) "0.5",       (const jerry_char_t *) "12345",
-    (const jerry_char_t *) "1e-45",     (const jerry_char_t *) "-2.5e+38",  (const jerry_char_t *) "-2.5e38",
-    (const jerry_char_t *) "- 2.5e+38", (const jerry_char_t *) "-2 .5e+38", (const jerry_char_t *) "-2. 5e+38",
-    (const jerry_char_t *) "-2.5e+ 38", (const jerry_char_t *) "-2.5 e+38", (const jerry_char_t *) "-2.5e +38",
-    (const jerry_char_t *) "NaN",       (const jerry_char_t *) "abc",       (const jerry_char_t *) "   Infinity  ",
-    (const jerry_char_t *) "-Infinity", (const jerry_char_t *) "0",         (const jerry_char_t *) "0",
+  jerry_string_t strings[] = {
+    { JERRY_ZSTR_ARG ("1") },         { JERRY_ZSTR_ARG ("0.5") },       { JERRY_ZSTR_ARG ("12345") },
+    { JERRY_ZSTR_ARG ("1e-45") },     { JERRY_ZSTR_ARG ("-2.5e+38") },  { JERRY_ZSTR_ARG ("-2.5e38") },
+    { JERRY_ZSTR_ARG ("- 2.5e+38") }, { JERRY_ZSTR_ARG ("-2 .5e+38") }, { JERRY_ZSTR_ARG ("-2. 5e+38") },
+    { JERRY_ZSTR_ARG ("-2.5e+ 38") }, { JERRY_ZSTR_ARG ("-2.5 e+38") }, { JERRY_ZSTR_ARG ("-2.5e +38") },
+    { JERRY_ZSTR_ARG ("NaN") },       { JERRY_ZSTR_ARG ("abc") },       { JERRY_ZSTR_ARG ("   Infinity  ") },
+    { JERRY_ZSTR_ARG ("-Infinity") }, { JERRY_ZSTR_ARG ("0") },         { JERRY_ZSTR_ARG ("0") },
   };
 
   const ecma_number_t nums[] = { (ecma_number_t) 1.0,       (ecma_number_t) 0.5,      (ecma_number_t) 12345.0,
@@ -46,7 +45,7 @@ main (void)
 
   for (uint32_t i = 0; i < sizeof (nums) / sizeof (nums[0]); i++)
   {
-    ecma_number_t num = ecma_utf8_string_to_number (strings[i], lit_zt_utf8_string_size (strings[i]), 0);
+    ecma_number_t num = ecma_utf8_string_to_number (strings[i].ptr, strings[i].size, 0);
 
     if (num != nums[i] && (!ecma_number_is_nan (num) || !ecma_number_is_nan (nums[i])))
     {
diff --git a/tests/unit-core/test-symbol.c b/tests/unit-core/test-symbol.c
index bbbc0c0173..064ee5deac 100644
--- a/tests/unit-core/test-symbol.c
+++ b/tests/unit-core/test-symbol.c
@@ -19,10 +19,10 @@
 #include "test-common.h"
 
 /* foo string */
-#define STRING_FOO ("foo")
+#define STRING_FOO "foo"
 
 /* bar string */
-#define STRING_BAR ("bar")
+#define STRING_BAR "bar"
 
 /* Symbol(bar) desciptive string */
 #define SYMBOL_DESCIPTIVE_STRING_BAR "Symbol(bar)"
@@ -38,8 +38,8 @@ main (void)
   jerry_value_t object = jerry_object ();
 
   /* Test for that each symbol is unique independently from their descriptor strings */
-  jerry_value_t symbol_desc_1 = jerry_string_sz (STRING_FOO);
-  jerry_value_t symbol_desc_2 = jerry_string_sz (STRING_FOO);
+  jerry_value_t symbol_desc_1 = jerry_sz_ascii (STRING_FOO);
+  jerry_value_t symbol_desc_2 = jerry_sz_ascii (STRING_FOO);
 
   jerry_value_t symbol_1 = jerry_symbol_with_description (symbol_desc_1);
   TEST_ASSERT (!jerry_value_is_exception (symbol_1));
@@ -99,7 +99,7 @@ main (void)
 
   /* Modify the descriptor fields */
   prop_desc = jerry_property_descriptor ();
-  jerry_value_t value_3 = jerry_string_sz (STRING_BAR);
+  jerry_value_t value_3 = jerry_sz_ascii (STRING_BAR);
 
   prop_desc.flags |= JERRY_PROP_IS_VALUE_DEFINED | JERRY_PROP_IS_WRITABLE_DEFINED | JERRY_PROP_IS_ENUMERABLE_DEFINED
                      | JERRY_PROP_IS_CONFIGURABLE_DEFINED;
@@ -130,7 +130,7 @@ main (void)
   jerry_value_free (object);
 
   /* Test creating symbol with a symbol description */
-  jerry_value_t empty_symbol_desc = jerry_string_sz ("");
+  jerry_value_t empty_symbol_desc = jerry_sz_ascii ("");
 
   jerry_value_t empty_symbol = jerry_symbol_with_description (empty_symbol_desc);
   TEST_ASSERT (!jerry_value_is_exception (empty_symbol));
@@ -150,7 +150,7 @@ main (void)
   jerry_value_free (empty_symbol);
 
   /* Test symbol to string operation with symbol argument */
-  jerry_value_t bar_symbol_desc = jerry_string_sz (STRING_BAR);
+  jerry_value_t bar_symbol_desc = jerry_sz_ascii (STRING_BAR);
 
   jerry_value_t bar_symbol = jerry_symbol_with_description (bar_symbol_desc);
   TEST_ASSERT (!jerry_value_is_exception (bar_symbol));
@@ -224,16 +224,19 @@ main (void)
                                  "  [Symbol.matchAll]: 13,"
                                  "})";
 
-  const char *symbols[] = {
-    "asyncIterator", "hasInstance", "isConcatSpreadable", "iterator",    "match",       "replace",  "search",
-    "species",       "split",       "toPrimitive",        "toStringTag", "unscopables", "matchAll",
+  const jerry_value_t symbols[] = {
+    jerry_sz_ascii ("asyncIterator"), jerry_sz_ascii ("hasInstance"), jerry_sz_ascii ("isConcatSpreadable"),
+    jerry_sz_ascii ("iterator"),      jerry_sz_ascii ("match"),       jerry_sz_ascii ("replace"),
+    jerry_sz_ascii ("search"),        jerry_sz_ascii ("species"),     jerry_sz_ascii ("split"),
+    jerry_sz_ascii ("toPrimitive"),   jerry_sz_ascii ("toStringTag"), jerry_sz_ascii ("unscopables"),
+    jerry_sz_ascii ("matchAll"),
   };
 
   jerry_value_t obj = jerry_eval (obj_src, sizeof (obj_src) - 1, JERRY_PARSE_NO_OPTS);
   TEST_ASSERT (jerry_value_is_object (obj));
 
   jerry_value_t global_obj = jerry_current_realm ();
-  jerry_value_t symbol_str = jerry_string_sz ("Symbol");
+  jerry_value_t symbol_str = jerry_sz_ascii ("Symbol");
   jerry_value_t builtin_symbol = jerry_object_get (global_obj, symbol_str);
   TEST_ASSERT (jerry_value_is_object (builtin_symbol));
 
@@ -245,9 +248,7 @@ main (void)
   {
     jerry_value_t well_known_symbol = jerry_symbol (id);
 
-    jerry_value_t prop_str = jerry_string_sz (symbols[prop_index]);
-    jerry_value_t current_global_symbol = jerry_object_get (builtin_symbol, prop_str);
-    jerry_value_free (prop_str);
+    jerry_value_t current_global_symbol = jerry_object_get (builtin_symbol, symbols[prop_index]);
 
     jerry_value_t relation = jerry_binary_op (JERRY_BIN_OP_STRICT_EQUAL, well_known_symbol, current_global_symbol);
 
@@ -272,6 +273,7 @@ main (void)
     jerry_value_free (well_known_symbol);
   }
 
+  jerry_value_list_free (symbols, sizeof (symbols) / symbols[0]);
   jerry_value_free (builtin_symbol);
 
   /* Deletion of the 'Symbol' builtin makes the well-known symbols unaccessible from JS context
diff --git a/tests/unit-core/test-to-property-descriptor.c b/tests/unit-core/test-to-property-descriptor.c
index 53821c27c1..f86ed548d7 100644
--- a/tests/unit-core/test-to-property-descriptor.c
+++ b/tests/unit-core/test-to-property-descriptor.c
@@ -29,9 +29,8 @@ create_property_descriptor (const char *script_p) /**< source code */
 static void
 check_attribute (jerry_value_t attribute, /**< attribute to be checked */
                  jerry_value_t object, /**< original object */
-                 const char *name_p) /**< name of the attribute */
+                 jerry_value_t prop_name) /**< name of the attribute that will be free/take */
 {
-  jerry_value_t prop_name = jerry_string_sz (name_p);
   jerry_value_t value = jerry_object_get (object, prop_name);
 
   if (jerry_value_is_undefined (value))
@@ -74,7 +73,7 @@ main (void)
 
   jerry_property_descriptor_t prop_desc = to_property_descriptor (object);
 
-  check_attribute (prop_desc.value, object, "value");
+  check_attribute (prop_desc.value, object, jerry_sz_ascii ("value"));
 
   TEST_ASSERT (prop_desc.flags & JERRY_PROP_IS_VALUE_DEFINED);
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_GET_DEFINED));
@@ -115,8 +114,8 @@ main (void)
 
   prop_desc = to_property_descriptor (object);
 
-  check_attribute (prop_desc.getter, object, "get");
-  check_attribute (prop_desc.setter, object, "set");
+  check_attribute (prop_desc.getter, object, jerry_sz_ascii ("get"));
+  check_attribute (prop_desc.setter, object, jerry_sz_ascii ("set"));
 
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_VALUE_DEFINED));
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_WRITABLE_DEFINED));
@@ -135,7 +134,7 @@ main (void)
 
   prop_desc = to_property_descriptor (object);
 
-  check_attribute (prop_desc.getter, object, "get");
+  check_attribute (prop_desc.getter, object, jerry_sz_ascii ("get"));
 
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_VALUE_DEFINED));
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_WRITABLE_DEFINED));
@@ -154,7 +153,7 @@ main (void)
 
   prop_desc = to_property_descriptor (object);
 
-  check_attribute (prop_desc.setter, object, "set");
+  check_attribute (prop_desc.setter, object, jerry_sz_ascii ("set"));
 
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_VALUE_DEFINED));
   TEST_ASSERT (!(prop_desc.flags & JERRY_PROP_IS_WRITABLE_DEFINED));
diff --git a/tests/unit-core/test-typedarray.c b/tests/unit-core/test-typedarray.c
index 78535b3e78..4c461005bb 100644
--- a/tests/unit-core/test-typedarray.c
+++ b/tests/unit-core/test-typedarray.c
@@ -26,7 +26,7 @@
 typedef struct
 {
   jerry_typedarray_type_t typedarray_type; /**< what kind of TypedArray */
-  char *constructor_name; /**< JS constructor name for TypedArray */
+  jerry_value_t constructor_name; /**< JS constructor name for TypedArray */
   uint32_t element_count; /**< number of elements for the TypedArray */
   uint32_t bytes_per_element; /**< bytes per elment of the given typedarray_type */
 } test_entry_t;
@@ -35,12 +35,11 @@ typedef struct
  * Register a JavaScript value in the global object.
  */
 static void
-register_js_value (const char *name_p, /**< name of the function */
+register_js_value (jerry_value_t name_val, /**< name of the function that will be free/take */
                    jerry_value_t value) /**< function callback */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
-  jerry_value_t name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (global_obj_val, name_val, value);
 
   jerry_value_free (name_val);
@@ -108,18 +107,16 @@ test_typedarray_queries (test_entry_t test_entries[]) /**< test cases */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
-  for (uint32_t i = 0; test_entries[i].constructor_name != NULL; i++)
+  for (uint32_t i = 0; !jerry_value_is_undefined (test_entries[i].constructor_name); i++)
   {
     /* Create TypedArray via construct call */
     {
-      jerry_value_t prop_name = jerry_string_sz (test_entries[i].constructor_name);
-      jerry_value_t prop_value = jerry_object_get (global_obj_val, prop_name);
+      jerry_value_t prop_value = jerry_object_get (global_obj_val, test_entries[i].constructor_name);
       TEST_ASSERT (!jerry_value_is_exception (prop_value));
       jerry_value_t length_arg = jerry_number (test_entries[i].element_count);
 
       jerry_value_t typedarray = jerry_construct (prop_value, &length_arg, 1);
 
-      jerry_value_free (prop_name);
       jerry_value_free (prop_value);
       jerry_value_free (length_arg);
 
@@ -223,7 +220,7 @@ test_typedarray_complex_creation (test_entry_t test_entries[], /**< test cases *
 {
   const uint32_t arraybuffer_size = 256;
 
-  for (uint32_t i = 0; test_entries[i].constructor_name != NULL; i++)
+  for (uint32_t i = 0; !jerry_value_is_undefined (test_entries[i].constructor_name); i++)
   {
     const uint32_t offset = 8;
     uint32_t element_count = test_entries[i].element_count;
@@ -248,8 +245,8 @@ test_typedarray_complex_creation (test_entry_t test_entries[], /**< test cases *
       jerry_value_t js_offset = jerry_number (offset);
       jerry_value_t js_element_count = jerry_number (element_count);
 
-      register_js_value ("expected_offset", js_offset);
-      register_js_value ("expected_length", js_element_count);
+      register_js_value (jerry_sz_ascii ("expected_offset"), js_offset);
+      register_js_value (jerry_sz_ascii ("expected_length"), js_element_count);
 
       typedarray =
         jerry_typedarray_with_buffer_span (test_entries[i].typedarray_type, arraybuffer, offset, element_count);
@@ -260,7 +257,7 @@ test_typedarray_complex_creation (test_entry_t test_entries[], /**< test cases *
       jerry_value_free (arraybuffer);
     }
 
-    register_js_value ("array", typedarray);
+    register_js_value (jerry_sz_ascii ("array"), typedarray);
 
     const jerry_char_t test_exptected_src[] =
       TEST_STRING_LITERAL ("assert (array.length == expected_length,"
@@ -324,7 +321,7 @@ test_property_by_index (test_entry_t test_entries[])
   uint64_t test_uint64_numbers[5] = { 83, 0, 1, UINT32_MAX, UINT64_MAX };
   int64_t test_int64_numbers[5] = { INT64_MAX, INT64_MIN, 0, INT32_MAX, INT32_MIN };
 
-  for (uint32_t i = 0; test_entries[i].constructor_name != NULL; i++)
+  for (uint32_t i = 0; !jerry_value_is_undefined (test_entries[i].constructor_name); i++)
   {
     jerry_value_t test_number;
     uint32_t test_numbers_length = sizeof (test_int_numbers) / sizeof (int);
@@ -496,6 +493,18 @@ test_property_by_index (test_entry_t test_entries[])
   }
 } /* test_property_by_index */
 
+/**
+ * Test entries free
+ */
+static void
+test_entries_free (test_entry_t test_entries[])
+{
+  for (uint32_t i = 0; !jerry_value_is_undefined (test_entries[i].constructor_name); i++)
+  {
+    jerry_value_free (test_entries[i].constructor_name);
+  }
+} /* test_entries_free */
+
 static void
 test_detached_arraybuffer (void)
 {
@@ -575,11 +584,12 @@ main (void)
   }
 
   jerry_value_t function_val = jerry_function_external (assert_handler);
-  register_js_value ("assert", function_val);
+  register_js_value (jerry_sz_ascii ("assert"), function_val);
   jerry_value_free (function_val);
 
   test_entry_t test_entries[] = {
-#define TEST_ENTRY(TYPE, CONSTRUCTOR, COUNT, BYTES_PER_ELEMENT) { TYPE, CONSTRUCTOR, COUNT, BYTES_PER_ELEMENT }
+#define TEST_ENTRY(TYPE, CONSTRUCTOR, COUNT, BYTES_PER_ELEMENT) \
+  { TYPE, jerry_sz_ascii (CONSTRUCTOR), COUNT, BYTES_PER_ELEMENT }
 
     TEST_ENTRY (JERRY_TYPEDARRAY_UINT8, "Uint8Array", 12, 1),
     TEST_ENTRY (JERRY_TYPEDARRAY_UINT8CLAMPED, "Uint8ClampedArray", 12, 1),
@@ -595,7 +605,7 @@ main (void)
     TEST_ENTRY (JERRY_TYPEDARRAY_BIGINT64, "BigInt64Array", 12, 8),
     TEST_ENTRY (JERRY_TYPEDARRAY_BIGUINT64, "BigUint64Array", 12, 8),
 
-    TEST_ENTRY (JERRY_TYPEDARRAY_INVALID, NULL, 0, 0)
+    { JERRY_TYPEDARRAY_INVALID, jerry_undefined (), 0, 0 }
 #undef TEST_ENTRY
   };
 
@@ -624,9 +634,9 @@ main (void)
       jerry_value_t js_element_count = jerry_number (element_count);
       jerry_value_t js_expected_value = jerry_number (expected_value);
 
-      register_js_value ("array", array);
-      register_js_value ("expected_length", js_element_count);
-      register_js_value ("expected_value", js_expected_value);
+      register_js_value (jerry_sz_ascii ("array"), array);
+      register_js_value (jerry_sz_ascii ("expected_length"), js_element_count);
+      register_js_value (jerry_sz_ascii ("expected_value"), js_expected_value);
 
       jerry_value_free (js_element_count);
       jerry_value_free (js_expected_value);
@@ -673,16 +683,18 @@ main (void)
 
   test_property_by_index (test_entries);
 
+  test_entries_free (test_entries);
+
   /* test invalid things */
   {
     jerry_value_t values[] = {
       jerry_number (11),
       jerry_boolean (false),
-      jerry_string_sz ("test"),
+      jerry_sz_ascii ("test"),
       jerry_object (),
       jerry_null (),
       jerry_arraybuffer (16),
-      jerry_error_sz (JERRY_ERROR_TYPE, "error"),
+      jerry_error_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("error")),
       jerry_undefined (),
       jerry_promise (),
     };
diff --git a/tests/unit-core/test-vm-exec-stop.c b/tests/unit-core/test-vm-exec-stop.c
index 41cadba354..8492e76a17 100644
--- a/tests/unit-core/test-vm-exec-stop.c
+++ b/tests/unit-core/test-vm-exec-stop.c
@@ -30,7 +30,7 @@ vm_exec_stop_callback (void *user_p)
     return jerry_undefined ();
   }
 
-  return jerry_string_sz ("Abort script");
+  return jerry_sz_ascii ("Abort script");
 } /* vm_exec_stop_callback */
 
 int
diff --git a/tests/unit-core/test-vm-throw.c b/tests/unit-core/test-vm-throw.c
index b4f2d20861..4115453176 100644
--- a/tests/unit-core/test-vm-throw.c
+++ b/tests/unit-core/test-vm-throw.c
@@ -100,7 +100,7 @@ native_handler (const jerry_call_info_t *call_info_p, /**< call info */
 
   if (mode == 7)
   {
-    jerry_value_t result = jerry_throw_sz (JERRY_ERROR_COMMON, "Error!");
+    jerry_value_t result = jerry_throw_sz (JERRY_ERROR_COMMON, jerry_sz_ascii ("Error!"));
 
     TEST_ASSERT (!jerry_exception_is_captured (result));
     jerry_exception_allow_capture (result, false);
@@ -185,7 +185,7 @@ main (void)
   /* Native functions may trigger the call twice: */
   jerry_value_t global_object_value = jerry_current_realm ();
   jerry_value_t function_value = jerry_function_external (native_handler);
-  jerry_value_t function_name_value = jerry_string_sz ("native");
+  jerry_value_t function_name_value = jerry_sz_ascii ("native");
 
   jerry_value_free (jerry_object_set (global_object_value, function_name_value, function_value));
   jerry_value_free (function_name_value);
diff --git a/tests/unit-ext/module/jerry-module-test.c b/tests/unit-ext/module/jerry-module-test.c
index d8352ed84c..435698f11a 100644
--- a/tests/unit-ext/module/jerry-module-test.c
+++ b/tests/unit-ext/module/jerry-module-test.c
@@ -202,7 +202,7 @@ main (int argc, char **argv)
   js_global = jerry_current_realm ();
 
   js_function = jerry_function_external (handle_require);
-  js_property_name = jerry_string_sz ("require");
+  js_property_name = jerry_sz_ascii ("require");
   res = jerry_object_set (js_global, js_property_name, js_function);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_boolean (res) && jerry_value_is_true (res));
@@ -211,7 +211,7 @@ main (int argc, char **argv)
   jerry_value_free (js_function);
 
   js_function = jerry_function_external (handle_clear_require_cache);
-  js_property_name = jerry_string_sz ("clear_require_cache");
+  js_property_name = jerry_sz_ascii ("clear_require_cache");
   res = jerry_object_set (js_global, js_property_name, js_function);
   TEST_ASSERT (!jerry_value_is_exception (res));
   TEST_ASSERT (jerry_value_is_boolean (res) && jerry_value_is_true (res));
diff --git a/tests/unit-ext/module/my-custom-module.c b/tests/unit-ext/module/my-custom-module.c
index 2395bfcf00..0809f7b505 100644
--- a/tests/unit-ext/module/my-custom-module.c
+++ b/tests/unit-ext/module/my-custom-module.c
@@ -20,9 +20,10 @@
 #define MODULE_NAME my_custom_module
 
 static void
-jobject_set_property_jval (jerry_value_t jobj, const char *name, jerry_value_t value)
+jobject_set_property_jval (jerry_value_t jobj,
+                           jerry_value_t prop_name, /**< property name value that will be free/take */
+                           jerry_value_t value)
 {
-  jerry_value_t prop_name = jerry_string_sz (name);
   jerry_value_t ret_val = jerry_object_set (jobj, prop_name, value);
   jerry_value_free (prop_name);
   jerry_value_free (ret_val);
@@ -43,11 +44,11 @@ my_custom_module_on_resolve (void)
 {
   jerry_value_t mymodule = jerry_object ();
   jerry_value_t val = jerry_number (42);
-  jobject_set_property_jval (mymodule, "number_value", val);
+  jobject_set_property_jval (mymodule, jerry_sz_ascii ("number_value"), val);
   jerry_value_free (val);
 
   jerry_value_t jfunc = jerry_function_external (call_function_with_callback);
-  jobject_set_property_jval (mymodule, "call_function_with_callback", jfunc);
+  jobject_set_property_jval (mymodule, jerry_sz_ascii ("call_function_with_callback"), jfunc);
   jerry_value_free (jfunc);
 
   return mymodule;
diff --git a/tests/unit-ext/test-common.h b/tests/unit-ext/test-common.h
index 5941f46184..562e9470cc 100644
--- a/tests/unit-ext/test-common.h
+++ b/tests/unit-ext/test-common.h
@@ -20,8 +20,6 @@
 
 #define ARRAY_SIZE(array) ((unsigned long) (sizeof (array) / sizeof ((array)[0])))
 
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define TEST_ASSERT(x)                                           \
   do                                                             \
   {                                                              \
diff --git a/tests/unit-ext/test-ext-arg.c b/tests/unit-ext/test-ext-arg.c
index d32b865833..44a6917573 100644
--- a/tests/unit-ext/test-ext-arg.c
+++ b/tests/unit-ext/test-ext-arg.c
@@ -183,7 +183,7 @@ my_custom_transform (jerryx_arg_js_iterator_t *js_arg_iter_p, /**< available JS
   {
     jerry_value_free (to_number);
 
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "It can not be converted to a number.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("It can not be converted to a number."));
   }
 
   int expected_num = (int) c_arg_p->extra_info;
@@ -191,7 +191,7 @@ my_custom_transform (jerryx_arg_js_iterator_t *js_arg_iter_p, /**< available JS
 
   if (get_num != expected_num)
   {
-    return jerry_throw_sz (JERRY_ERROR_TYPE, "Number value is not expected.");
+    return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("Number value is not expected."));
   }
 
   return jerry_undefined ();
@@ -311,18 +311,16 @@ test_validator_prop1_handler (const jerry_call_info_t *call_info_p, /**< call in
   double native2 = 0;
   double native3 = 3;
 
-  const char *name_p[] = { "prop1", "prop2", "prop3" };
+  const jerry_value_t name_p[] = { jerry_sz_ascii ("prop1"), jerry_sz_ascii ("prop2"), jerry_sz_ascii ("prop3") };
 
   jerryx_arg_t mapping[] = { jerryx_arg_boolean (&native1, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
                              jerryx_arg_number (&native2, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
                              jerryx_arg_number (&native3, JERRYX_ARG_COERCE, JERRYX_ARG_OPTIONAL) };
 
-  jerry_value_t is_ok = jerryx_arg_transform_object_properties (args_p[0],
-                                                                (const jerry_char_t **) name_p,
-                                                                ARRAY_SIZE (name_p),
-                                                                mapping,
-                                                                ARRAY_SIZE (mapping));
+  jerry_value_t is_ok =
+    jerryx_arg_transform_object_properties (args_p[0], name_p, ARRAY_SIZE (name_p), mapping, ARRAY_SIZE (mapping));
 
+  jerry_value_list_free (name_p, ARRAY_SIZE (name_p));
   TEST_ASSERT (!jerry_value_is_exception (is_ok));
   TEST_ASSERT (native1);
   TEST_ASSERT (native2 == 1.5);
@@ -350,13 +348,13 @@ test_validator_prop2_handler (const jerry_call_info_t *call_info_p, /**< call in
 
   jerryx_arg_object_props_t prop_info;
 
-  const char *name_p[] = { "prop1", "prop2", "prop3" };
+  const jerry_value_t name_p[] = { jerry_sz_ascii ("prop1"), jerry_sz_ascii ("prop2"), jerry_sz_ascii ("prop3") };
 
   jerryx_arg_t prop_mapping[] = { jerryx_arg_boolean (&native1, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
                                   jerryx_arg_number (&native2, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
                                   jerryx_arg_number (&native3, JERRYX_ARG_COERCE, JERRYX_ARG_OPTIONAL) };
 
-  prop_info.name_p = (const jerry_char_t **) name_p;
+  prop_info.name_p = name_p;
   prop_info.name_cnt = 3;
   prop_info.c_arg_p = prop_mapping;
   prop_info.c_arg_cnt = 3;
@@ -367,6 +365,7 @@ test_validator_prop2_handler (const jerry_call_info_t *call_info_p, /**< call in
 
   jerry_value_t is_ok = jerryx_arg_transform_args (args_p, args_cnt, mapping, ARRAY_SIZE (mapping));
 
+  jerry_value_list_free (name_p, ARRAY_SIZE (name_p));
   TEST_ASSERT (!jerry_value_is_exception (is_ok));
 
   if (validator_prop_count == 1)
@@ -392,19 +391,17 @@ test_validator_prop3_handler (const jerry_call_info_t *call_info_p, /**< call in
   bool native1 = false;
   bool native2 = true;
 
-  const char *name_p[] = { "prop1", "prop2" };
+  const jerry_value_t name_p[] = { jerry_sz_ascii ("prop1"), jerry_sz_ascii ("prop2") };
 
   jerryx_arg_t mapping[] = {
     jerryx_arg_boolean (&native1, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
     jerryx_arg_boolean (&native2, JERRYX_ARG_COERCE, JERRYX_ARG_REQUIRED),
   };
 
-  jerry_value_t is_ok = jerryx_arg_transform_object_properties (args_p[0],
-                                                                (const jerry_char_t **) name_p,
-                                                                ARRAY_SIZE (name_p),
-                                                                mapping,
-                                                                ARRAY_SIZE (mapping));
+  jerry_value_t is_ok =
+    jerryx_arg_transform_object_properties (args_p[0], name_p, ARRAY_SIZE (name_p), mapping, ARRAY_SIZE (mapping));
 
+  jerry_value_list_free (name_p, ARRAY_SIZE (name_p));
   TEST_ASSERT (jerry_value_is_exception (is_ok));
   TEST_ASSERT (!native1);
   TEST_ASSERT (native2);
@@ -718,7 +715,7 @@ jerry_arg_to_double_or_bool_t (jerryx_arg_js_iterator_t *js_arg_iter_p, const je
   /* Fall through indicates that whatever they gave us, it wasn't
    * one of the types we were expecting... */
   jerry_value_free (conversion_result);
-  return jerry_throw_sz (JERRY_ERROR_TYPE, "double_or_bool-type error.");
+  return jerry_throw_sz (JERRY_ERROR_TYPE, jerry_sz_ascii ("double_or_bool-type error."));
 } /* jerry_arg_to_double_or_bool_t */
 
 /**
@@ -758,7 +755,7 @@ static void
 test_utf8_string (void)
 {
   /* test string: 'str: {DESERET CAPITAL LETTER LONG I}' */
-  jerry_value_t str = jerry_string_sz ("\x73\x74\x72\x3a \xed\xa0\x81\xed\xb0\x80");
+  jerry_value_t str = jerry_sz_cesu8 ("\x73\x74\x72\x3a \xed\xa0\x81\xed\xb0\x80");
   char expect_utf8_buf[] = "\x73\x74\x72\x3a \xf0\x90\x90\x80";
   size_t buf_len = sizeof (expect_utf8_buf) - 1;
   JERRY_VLA (char, buf, buf_len + 1);
@@ -811,13 +808,12 @@ create_object_b_handler (const jerry_call_info_t *call_info_p, /**< call informa
  * Register a JavaScript function in the global object.
  */
 static void
-register_js_function (const char *name_p, /**< name of the function */
+register_js_function (jerry_value_t function_name_val, /**< name of the function that will be free/take */
                       jerry_external_handler_t handler_p) /**< function callback */
 {
   jerry_value_t global_obj_val = jerry_current_realm ();
 
   jerry_value_t function_val = jerry_function_external (handler_p);
-  jerry_value_t function_name_val = jerry_string_sz (name_p);
   jerry_value_t result_val = jerry_object_set (global_obj_val, function_name_val, function_val);
 
   jerry_value_free (function_name_val);
@@ -834,20 +830,20 @@ main (void)
 
   test_utf8_string ();
 
-  register_js_function ("test_validator1", test_validator1_handler);
-  register_js_function ("test_validator2", test_validator2_handler);
-  register_js_function ("test_validator3", test_validator3_handler);
-  register_js_function ("test_validator_int1", test_validator_int1_handler);
-  register_js_function ("test_validator_int2", test_validator_int2_handler);
-  register_js_function ("test_validator_int3", test_validator_int3_handler);
-  register_js_function ("MyObjectA", create_object_a_handler);
-  register_js_function ("MyObjectB", create_object_b_handler);
-  register_js_function ("test_validator_prop1", test_validator_prop1_handler);
-  register_js_function ("test_validator_prop2", test_validator_prop2_handler);
-  register_js_function ("test_validator_prop3", test_validator_prop3_handler);
-  register_js_function ("test_validator_array1", test_validator_array1_handler);
-  register_js_function ("test_validator_array2", test_validator_array2_handler);
-  register_js_function ("test_validator_restore", test_validator_restore_handler);
+  register_js_function (jerry_sz_ascii ("test_validator1"), test_validator1_handler);
+  register_js_function (jerry_sz_ascii ("test_validator2"), test_validator2_handler);
+  register_js_function (jerry_sz_ascii ("test_validator3"), test_validator3_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_int1"), test_validator_int1_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_int2"), test_validator_int2_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_int3"), test_validator_int3_handler);
+  register_js_function (jerry_sz_ascii ("MyObjectA"), create_object_a_handler);
+  register_js_function (jerry_sz_ascii ("MyObjectB"), create_object_b_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_prop1"), test_validator_prop1_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_prop2"), test_validator_prop2_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_prop3"), test_validator_prop3_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_array1"), test_validator_array1_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_array2"), test_validator_array2_handler);
+  register_js_function (jerry_sz_ascii ("test_validator_restore"), test_validator_restore_handler);
 
   jerry_value_t parsed_code_val = jerry_parse (test_source, sizeof (test_source) - 1, NULL);
   TEST_ASSERT (!jerry_value_is_exception (parsed_code_val));
diff --git a/tests/unit-ext/test-ext-method-register.c b/tests/unit-ext/test-ext-method-register.c
index 566ea9c6c7..ca39832da4 100644
--- a/tests/unit-ext/test-ext-method-register.c
+++ b/tests/unit-ext/test-ext-method-register.c
@@ -39,13 +39,12 @@ method_hello (const jerry_call_info_t *call_info_p, /**< call information */
  */
 static void
 freeze_property (jerry_value_t target_obj, /**< target object */
-                 const char *target_prop) /**< target property name */
+                 jerry_value_t prop_name) /**< target property name that will be free/take */
 {
   // "freeze" property
   jerry_property_descriptor_t prop_desc = jerry_property_descriptor ();
   prop_desc.flags |= JERRY_PROP_IS_CONFIGURABLE_DEFINED;
 
-  jerry_value_t prop_name = jerry_string_sz (target_prop);
   jerry_value_t return_value = jerry_object_define_own_prop (target_obj, prop_name, &prop_desc);
   TEST_ASSERT (jerry_value_is_boolean (return_value));
   jerry_value_free (return_value);
@@ -81,7 +80,7 @@ test_simple_registration (void)
   jerry_value_free (register_result.result);
 
   jerry_value_t global_obj = jerry_current_realm ();
-  jerry_object_set_sz (global_obj, "test", target_object);
+  jerry_object_set_sz (global_obj, jerry_sz_ascii ("test"), target_object);
   jerry_value_free (target_object);
   jerry_value_free (global_obj);
 
@@ -162,12 +161,12 @@ test_error_setvalue (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  const char *target_prop = "test_err";
+#define target_prop "test_err"
   jerry_value_t global_obj = jerry_current_realm ();
-  freeze_property (global_obj, target_prop);
+  freeze_property (global_obj, jerry_sz_ascii (target_prop));
 
   jerry_value_t new_object = jerry_object ();
-  jerry_value_t set_result = jerry_object_set_sz (global_obj, target_prop, new_object);
+  jerry_value_t set_result = jerry_object_set_sz (global_obj, jerry_sz_ascii (target_prop), new_object);
   TEST_ASSERT (jerry_value_is_exception (set_result));
 
   jerry_value_free (set_result);
@@ -188,9 +187,9 @@ test_error_single_function (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  const char *target_prop = "test_err";
+#define target_prop "test_err"
   jerry_value_t target_object = jerry_object ();
-  freeze_property (target_object, target_prop);
+  freeze_property (target_object, jerry_sz_ascii (target_prop));
 
   jerryx_property_entry methods[] = {
     JERRYX_PROPERTY_FUNCTION (target_prop, method_hello), // This registration should fail
@@ -217,11 +216,11 @@ test_error_multiple_functions (void)
 {
   jerry_init (JERRY_INIT_EMPTY);
 
-  const char *prop_ok = "prop_ok";
-  const char *prop_err = "prop_err";
-  const char *prop_not = "prop_not";
+#define prop_ok  "prop_ok"
+#define prop_err "prop_err"
+#define prop_not "prop_not"
   jerry_value_t target_object = jerry_object ();
-  freeze_property (target_object, prop_err);
+  freeze_property (target_object, jerry_sz_ascii (prop_err));
 
   jerryx_property_entry methods[] = {
     JERRYX_PROPERTY_FUNCTION (prop_ok, method_hello), // This registration is ok
@@ -240,7 +239,7 @@ test_error_multiple_functions (void)
 
   {
     // Test if property "prop_ok" is correctly registered.
-    jerry_value_t prop_ok_val = jerry_string_sz (prop_ok);
+    jerry_value_t prop_ok_val = jerry_sz_ascii (prop_ok);
     jerry_value_t prop_ok_exists = jerry_object_has_own (target_object, prop_ok_val);
     TEST_ASSERT (jerry_value_is_true (prop_ok_exists));
     jerry_value_free (prop_ok_exists);
@@ -267,7 +266,7 @@ test_error_multiple_functions (void)
 
   {
     // The "prop_err" should exist - as it was "freezed" - but it should not be a function
-    jerry_value_t prop_err_val = jerry_string_sz (prop_err);
+    jerry_value_t prop_err_val = jerry_sz_ascii (prop_err);
     jerry_value_t prop_err_exists = jerry_object_has_own (target_object, prop_err_val);
     TEST_ASSERT (jerry_value_is_true (prop_err_exists));
     jerry_value_free (prop_err_exists);
@@ -278,7 +277,7 @@ test_error_multiple_functions (void)
   }
 
   { // The "prop_not" is not available on the target object
-    jerry_value_t prop_not_val = jerry_string_sz (prop_not);
+    jerry_value_t prop_not_val = jerry_sz_ascii (prop_not);
     jerry_value_t prop_not_exists = jerry_object_has_own (target_object, prop_not_val);
     TEST_ASSERT (jerry_value_is_true (prop_not_exists) == false);
     jerry_value_free (prop_not_exists);
diff --git a/tests/unit-ext/test-ext-module-canonical.c b/tests/unit-ext/test-ext-module-canonical.c
index 8bad59f8ca..9e95a18463 100644
--- a/tests/unit-ext/test-ext-module-canonical.c
+++ b/tests/unit-ext/test-ext-module-canonical.c
@@ -37,7 +37,7 @@ get_canonical_name (const jerry_value_t name)
   }
   else if (!strcmp ((char *) name_string, ALIAS_NAME))
   {
-    return jerry_string_sz (ACTUAL_NAME);
+    return jerry_sz_ascii (ACTUAL_NAME);
   }
   else
   {
@@ -76,8 +76,8 @@ main (int argc, char **argv)
 
   jerry_init (JERRY_INIT_EMPTY);
 
-  jerry_value_t actual_name = jerry_string_sz (ACTUAL_NAME);
-  jerry_value_t alias_name = jerry_string_sz (ALIAS_NAME);
+  jerry_value_t actual_name = jerry_sz_ascii (ACTUAL_NAME);
+  jerry_value_t alias_name = jerry_sz_ascii (ALIAS_NAME);
 
   /* It's important that we resolve by the non-canonical name first. */
   jerry_value_t result2 = jerryx_module_resolve (alias_name, &resolver, 1);
@@ -86,7 +86,7 @@ main (int argc, char **argv)
   jerry_value_free (alias_name);
 
   /* An elaborate way of doing strict equal - set a property on one object and it "magically" appears on the other. */
-  jerry_value_t prop_name = jerry_string_sz ("something");
+  jerry_value_t prop_name = jerry_sz_ascii ("something");
   jerry_value_t prop_value = jerry_number (TEST_VALUE);
   jerry_value_free (jerry_object_set (result1, prop_name, prop_value));
   jerry_value_free (prop_value);
diff --git a/tests/unit-ext/test-ext-module-empty.c b/tests/unit-ext/test-ext-module-empty.c
index 353b2fa266..bf1b75c42c 100644
--- a/tests/unit-ext/test-ext-module-empty.c
+++ b/tests/unit-ext/test-ext-module-empty.c
@@ -33,7 +33,7 @@ main (int argc, char **argv)
   jerry_init (JERRY_INIT_EMPTY);
 
   /* Attempt to load a non-existing module. */
-  module_name = jerry_string_sz ("some-unknown-module-name");
+  module_name = jerry_sz_ascii ("some-unknown-module-name");
   jerry_value_t module = jerryx_module_resolve (module_name, &resolver, 1);
   jerry_value_free (module_name);
 
@@ -41,7 +41,7 @@ main (int argc, char **argv)
 
   /* Retrieve the error message. */
   module = jerry_exception_value (module, true);
-  jerry_value_t prop_name = jerry_string_sz ("message");
+  jerry_value_t prop_name = jerry_sz_ascii ("message");
   jerry_value_t prop = jerry_object_get (module, prop_name);
 
   /* Assert that the error message is a string with specific contents. */
@@ -56,7 +56,7 @@ main (int argc, char **argv)
   jerry_value_free (prop_name);
 
   /* Retrieve the moduleName property. */
-  prop_name = jerry_string_sz ("moduleName");
+  prop_name = jerry_sz_ascii ("moduleName");
   prop = jerry_object_get (module, prop_name);
 
   /* Assert that the moduleName property is a string containing the requested module name. */