diff --git a/README.md b/README.md
index dbfaa0f..54dd5ad 100644
--- a/README.md
+++ b/README.md
@@ -58,6 +58,9 @@ services:
       # https://immich.app/docs/features/command-line-interface#obtain-the-api-key
       API_KEY: xxxxxxxxxxxxxxxxx
 
+      # This is default. Can be omitted. When true, prints output but does not submit any changes
+      DRY_RUN: False
+
       # Whether or not to modify photos that are already in stacks. Going over all assets takes a lot more time.
       SKIP_PREVIOUS: True
 
diff --git a/immich_auto_stack.py b/immich_auto_stack.py
index 25a24c4..ee20442 100644
--- a/immich_auto_stack.py
+++ b/immich_auto_stack.py
@@ -171,11 +171,16 @@ def main():
 
   skip_previous = str2bool(os.environ.get("SKIP_PREVIOUS", True))
 
+  dry_run = str2bool(os.environ.get("DRY_RUN", False))
+
   if not api_key:
     logger.warn("API key is required")
     return
 
   logger.info('============== INITIALIZING ==============')
+
+  if dry_run:
+    logger.info('🔒  Dry run enabled, no changes will be applied')
   
   immich = Immich(api_url, api_key)
   
@@ -213,8 +218,9 @@ def main():
         "stackParentId": parent_id
       }
 
-      time.sleep(.1)
-      immich.modifyAssets(payload)
+      if not dry_run:
+        time.sleep(.1)
+        immich.modifyAssets(payload)
 
 if __name__ == '__main__':
   main()
diff --git a/tests/test_dry_run.py b/tests/test_dry_run.py
new file mode 100644
index 0000000..58df4f6
--- /dev/null
+++ b/tests/test_dry_run.py
@@ -0,0 +1,58 @@
+import os
+import pytest
+from unittest.mock import patch, Mock
+
+from immich_auto_stack import main
+
+
+@pytest.mark.parametrize(
+    "dry_run_env_var,expected_call_count",
+    [
+        ("True", 0),
+        ("true", 0),
+        ("yes", 0),
+        ("False", 1),
+        ("no", 1),
+        ("0", 1),
+        ("", 1),
+        (None, 1),
+    ],
+)
+@patch("immich_auto_stack.stratifyStack")
+@patch("immich_auto_stack.stackBy")
+@patch("immich_auto_stack.Immich")
+def test_main_applies_dry_run_env_var_to_skip_modifyAssets(
+    mock_immich_class,
+    mock_stackBy,
+    mock_stratifyStack,
+    dry_run_env_var,
+    expected_call_count,
+):
+    # Arrange
+    # mock the function calls within main() to create predictable scenarios
+    mock_stackBy.return_value = [
+        (
+            "dummy_key",
+            [
+                {"id": "parent", "originalFileName": "foo.jpg"},
+                {
+                    "id": "child",
+                    "originalFileName": "foo.png",
+                },
+            ],
+        )
+    ]
+    mock_stratifyStack.side_effect = lambda x: x  # Return the same value passed in
+    test_environ = {
+        "API_KEY": "123",
+        "API_URL": "456",
+    }
+    if dry_run_env_var is not None:
+        test_environ["DRY_RUN"] = dry_run_env_var
+
+    # Act
+    with patch.dict(os.environ, test_environ):
+        main()
+
+    # Assert
+    assert mock_immich_class().modifyAssets.call_count == expected_call_count