diff --git a/.gitignore b/.gitignore
index b30921b1..92ebc14a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 node_modules
 README.html
-.tern-port
\ No newline at end of file
+.tern-port
+package-lock.json
\ No newline at end of file
diff --git a/README.md b/README.md
index c0e2d63b..1589ed62 100644
--- a/README.md
+++ b/README.md
@@ -83,6 +83,8 @@ test('should mock "await import()" using esmock.p', async t => {
    <summary>changelog</summary>
    <br/>
 
+ * 1.6.0 _Dec.02.2021_
+   * reduce file url length (improve readability of stacktrace)
  * 1.5.0 _Dec.01.2021_
    * resolve bug around error '--loader=esmock' detection
  * 1.4.0 _Nov.30.2021_
diff --git a/package.json b/package.json
index d74f4d63..c5e3cd11 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "esmock",
-  "version": "1.5.0",
+  "version": "1.6.0",
   "license": "MIT",
   "readmeFilename": "README.md",
   "description": "provides native ESM import mocking for unit tests",
diff --git a/spec/esmock.spec.js b/spec/esmock.spec.js
index 46d0b672..7f96457a 100644
--- a/spec/esmock.spec.js
+++ b/spec/esmock.spec.js
@@ -283,7 +283,7 @@ test('mocks inline `async import("name")`', async t => {
       filePath : 'filePath'
     }));
 
-  const [ , key ] = writeJSConfigFile.esmockKey.match(/esmockKey=(\d*)/);
+  const [ , key ] = writeJSConfigFile.esmockKey.match(/esmk=(\d*)/);
   const keyRe = new RegExp(`esmockKey=${key}[^d]`);
 
   const moduleKeys = Object.keys(esmock.esmockCache.mockDefs)
@@ -293,3 +293,15 @@ test('mocks inline `async import("name")`', async t => {
   esmock.purge(writeJSConfigFile);
   t.true(moduleKeys.every(mkey => esmock.esmockCache.mockDefs[mkey] === null));
 });
+
+test('should have small querystring in stacktrace filename', async t => {
+  const { causeRuntimeError } = await esmock('./local/mainUtil.js');
+
+  try {
+    causeRuntimeError();
+  } catch (e) {
+    t.true(/\?esmk=\d/.test(e.stack.split('\n')[1]));
+  }
+
+  t.pass();
+});
diff --git a/src/esmockCache.js b/src/esmockCache.js
index 5a377e63..96129b3a 100644
--- a/src/esmockCache.js
+++ b/src/esmockCache.js
@@ -6,6 +6,12 @@ const esmockCache = {
   mockDefs : {}
 };
 
+const esmockKeySet = (key, keylong) => (
+  global.mockKeys[String(key)] = keylong);
+
+const esmockKeyGet = key => (
+  global.mockKeys[String(key)]);
+
 const esmockCacheSet = (key, mockDef) => (
   esmockCache.mockDefs[key] = mockDef);
 
@@ -18,12 +24,18 @@ const esmockCacheResolvedPathIsESMGet = mockPathFull => (
 const esmockCacheResolvedPathIsESMSet = (mockPathFull, isesm) => (
   esmockCache.isESM[mockPathFull] = isesm);
 
-Object.assign(global, { esmockCacheGet });
+Object.assign(global, {
+  esmockCacheGet,
+  esmockKeyGet,
+  mockKeys : {}
+});
 
 export {
   esmockCache,
   esmockCacheSet,
   esmockCacheGet,
+  esmockKeySet,
+  esmockKeyGet,
   esmockCacheResolvedPathIsESMGet,
   esmockCacheResolvedPathIsESMSet
 };
diff --git a/src/esmockLoader.mjs b/src/esmockLoader.mjs
index bbd8b314..ee098ada 100644
--- a/src/esmockLoader.mjs
+++ b/src/esmockLoader.mjs
@@ -12,9 +12,15 @@ const urlDummy = 'file:///' + path
   .replace(/^\//, '');
 
 const resolve = async (specifier, context, defaultResolve) => {
-  const [ esmockKeyParam ] = (context.parentURL
-    && context.parentURL.match(/esmockKey=\d*/) || []);
-
+  const { parentURL } = context;
+  const [ esmockKeyParamSmall ] =
+    (parentURL && parentURL.match(/\?esmk=\d*/)) || [];
+  const esmockKeyLong = esmockKeyParamSmall
+    ? global.esmockKeyGet(esmockKeyParamSmall.split('=')[1])
+    : parentURL;
+  const [ esmockKeyParam ] =
+    (esmockKeyLong && esmockKeyLong.match(/esmockKey=\d*/) || []);
+  
   if (!esmockKeyParam)
     return defaultResolve(specifier, context, defaultResolve);
 
@@ -22,7 +28,7 @@ const resolve = async (specifier, context, defaultResolve) => {
   const moduleKeyRe = new RegExp(
     '.*(' + resolved.url + '\\?' + esmockKeyParam + '[^#]*).*');
 
-  const moduleURLSplitKeys = context.parentURL.split('#esmockModuleKeys=');
+  const moduleURLSplitKeys = esmockKeyLong.split('#esmockModuleKeys=');
   // eslint-disable-next-line prefer-destructuring
   const moduleGlobals = moduleURLSplitKeys[0].split('?esmockGlobals=')[1];
   const moduleKeyChild = moduleKeyRe.test(moduleURLSplitKeys[1])
diff --git a/src/esmockModule.js b/src/esmockModule.js
index 1b30d0af..3c7029eb 100644
--- a/src/esmockModule.js
+++ b/src/esmockModule.js
@@ -3,6 +3,8 @@ import path from 'path';
 import resolvewith from 'resolvewithplus';
 
 import {
+  esmockKeySet,
+  esmockKeyGet,
   esmockCacheSet,
   esmockCacheResolvedPathIsESMGet,
   esmockCacheResolvedPathIsESMSet
@@ -68,7 +70,7 @@ const esmockModuleIsESM = (mockPathFull, isesm) => {
 // does not need to lookup default as in "esmockedValue.default"
 const esmockModuleImportedSanitize = (importedModule, esmockKey) => {
   const importedDefault = 'default' in importedModule && importedModule.default;
-  
+
   if (!/boolean|string|number/.test(typeof importedDefault)) {
     // an example of [object Module]: import * as mod from 'fs'; export mod;
     return Object.prototype.toString.call(importedDefault) === '[object Module]'
@@ -81,7 +83,8 @@ const esmockModuleImportedSanitize = (importedModule, esmockKey) => {
 
 const esmockModuleImportedPurge = modulePathKey => {
   const purgeKey = key => key === 'null' || esmockCacheSet(key, null);
-  const [ url, keys ] = modulePathKey.split('#esmockModuleKeys=');
+  const longKey = esmockKeyGet(modulePathKey.split('esmk=')[1]);
+  const [ url, keys ] = longKey.split('#esmockModuleKeys=');
 
   String(keys).split('#').forEach(purgeKey);
   String(url.split('esmockGlobals=')[1]).split('#').forEach(purgeKey);
@@ -148,11 +151,15 @@ const esmockModuleMock = async (calleePath, modulePath, defs, gdefs, opt) => {
   if (pathModuleFull === null)
     throw new Error(`modulePath not found: "${modulePath}"`);
     
-  return pathAddProtocol(pathModuleFull, 'file:///') + '?'
+  const esmockKeyLong = pathAddProtocol(pathModuleFull, 'file:///') + '?'
     + 'key=:esmockKey?esmockGlobals=:esmockGlobals#esmockModuleKeys=:moduleKeys'
       .replace(/:esmockKey/, esmockKey)
       .replace(/:esmockGlobals/, esmockGlobalKeys.join('#') || 'null')
       .replace(/:moduleKeys/, esmockModuleKeys.join('#'));
+
+  esmockKeySet(String(esmockKey), esmockKeyLong);
+
+  return pathAddProtocol(pathModuleFull, 'file:///') + `?esmk=${esmockKey}`;
 };
 
 export {