diff --git a/browser/base/content/test/general/file_trackingUI_6.html b/browser/base/content/test/general/file_trackingUI_6.html
index 52e1ae63ffd7..a0fd3054b4f1 100644
--- a/browser/base/content/test/general/file_trackingUI_6.html
+++ b/browser/base/content/test/general/file_trackingUI_6.html
@@ -6,7 +6,7 @@
 </head>
 <body>
   <p>Hello there!</p>
-  <script type="application/javascript; version=1.8">
+  <script type="application/javascript">
     function test_fetch() {
       let url = "http://trackertest.org/browser/browser/base/content/test/general/file_trackingUI_6.js";
       return fetch(url);
diff --git a/devtools/client/shared/components/test/mochitest/test_HSplitBox_01.html b/devtools/client/shared/components/test/mochitest/test_HSplitBox_01.html
index e717fca20be6..d65bbe70bebb 100644
--- a/devtools/client/shared/components/test/mochitest/test_HSplitBox_01.html
+++ b/devtools/client/shared/components/test/mochitest/test_HSplitBox_01.html
@@ -10,7 +10,7 @@ Basic tests for the HSplitBox component.
   <meta charset="utf-8">
   <title>Tree component test</title>
   <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
-  <script type="application/javascript "src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+  <script type="application/javascript" src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
   <link rel="stylesheet" type="text/css" href="chrome://mochikit/content/tests/SimpleTest/test.css"/>
   <link rel="stylesheet" href="resource://devtools/client/themes/splitters.css" type="text/css"/>
   <link rel="stylesheet" href="chrome://devtools/skin/components-h-split-box.css" type="text/css"/>
diff --git a/devtools/client/storage/test/storage-cookies-samesite.html b/devtools/client/storage/test/storage-cookies-samesite.html
index ca91e1fb59c3..c14e2c67a839 100644
--- a/devtools/client/storage/test/storage-cookies-samesite.html
+++ b/devtools/client/storage/test/storage-cookies-samesite.html
@@ -5,7 +5,7 @@
     <title>Storage inspector cookie samesite test</title>
   </head>
   <body>
-    <script type="application/javascript;version=1.7">
+    <script type="application/javascript">
     "use strict";
     let expiresIn24Hours = new Date(Date.now() + 60 * 60 * 24 * 1000).toUTCString();
 
diff --git a/dom/html/test/test_checked.html b/dom/html/test/test_checked.html
index a445106234f7..eb021ea3df08 100644
--- a/dom/html/test/test_checked.html
+++ b/dom/html/test/test_checked.html
@@ -26,7 +26,7 @@ and
   </menu>
 </div>
 <pre id="test">
-<script class="testbody" type="text/javascript; version=1.7">
+<script class="testbody" type="text/javascript">
 
 /** Test for Bug 418756 and 617528 **/
 var group1;
diff --git a/dom/tests/mochitest/bugs/test_bug1171215.html b/dom/tests/mochitest/bugs/test_bug1171215.html
index af0d3c6a2fef..6b4f59ed9eae 100644
--- a/dom/tests/mochitest/bugs/test_bug1171215.html
+++ b/dom/tests/mochitest/bugs/test_bug1171215.html
@@ -10,7 +10,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1022869
   <script type="application/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
   <iframe src="about:blank"></iframe>
-  <script type="text/javascript; version=1.8">
+  <script type="text/javascript">
 
   var f = document.getElementsByTagName("iframe")[0];
 
diff --git a/dom/tests/mochitest/bugs/test_no_find_showDialog.html b/dom/tests/mochitest/bugs/test_no_find_showDialog.html
index fee670023d5a..e404c2976b03 100644
--- a/dom/tests/mochitest/bugs/test_no_find_showDialog.html
+++ b/dom/tests/mochitest/bugs/test_no_find_showDialog.html
@@ -7,7 +7,7 @@
   <script type="application/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
   <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
   <iframe src="about:blank"></iframe>
-  <script type="text/javascript; version=1.8">
+  <script type="text/javascript">
 
   function checkForFindDialog() {
     let chromeScript = SpecialPowers.loadChromeScript(_ => {
@@ -89,4 +89,4 @@
 <pre id="test">
 </pre>
 </body>
-</html>
\ No newline at end of file
+</html>
diff --git a/dom/xbl/test/test_bug389322.xhtml b/dom/xbl/test/test_bug389322.xhtml
index 4b80346bd275..c81e11143a5d 100644
--- a/dom/xbl/test/test_bug389322.xhtml
+++ b/dom/xbl/test/test_bug389322.xhtml
@@ -105,21 +105,13 @@ function report(testName, success) {
 }
 ]]>
 </script>
-<script type="text/javascript; version=1.7"><![CDATA[
-  try {
-    eval("let x = 1;");
-    var success = true;
-  }
-  catch (e) { success = false; }
-  report("HTML script tags with explicit version", success)
-]]></script>
 <script type="text/javascript"><![CDATA[
   try {
     eval("let x = 1;");
     var success = true;
   }
   catch (e) { success = false; }
-  is(success, true, "let should work in versionless HTML script tags");
+  is(success, true, "let should work in HTML script tags");
 ]]></script>
 </pre>
 </body>
diff --git a/layout/style/test/bug453896_iframe.html b/layout/style/test/bug453896_iframe.html
index bca68c7e7ac1..5a1f9e5b378c 100644
--- a/layout/style/test/bug453896_iframe.html
+++ b/layout/style/test/bug453896_iframe.html
@@ -5,7 +5,7 @@
   <title>Bug 453896 Test middle frame</title>
   <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
   <meta http-equiv="Content-Style-Type" content="text/css">
-  <script type="application/javascript; version=1.7">
+  <script type="application/javascript">
 
 function run(test_window)
 {
diff --git a/layout/style/test/chrome/test_moz_document_rules.html b/layout/style/test/chrome/test_moz_document_rules.html
index f2759c0850c3..233c53bf3ddc 100644
--- a/layout/style/test/chrome/test_moz_document_rules.html
+++ b/layout/style/test/chrome/test_moz_document_rules.html
@@ -10,7 +10,7 @@
 <a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=398962">Mozilla Bug 398962</a>
 <iframe id="iframe" src="http://mochi.test:8888/tests/layout/style/test/chrome/moz_document_helper.html"></iframe>
 <pre id="test">
-<script type="application/javascript; version=1.8">
+<script type="application/javascript">
 
 var [gStyleSheetService, gIOService] = (function() {
     return [
diff --git a/layout/style/test/test_addSheet.html b/layout/style/test/test_addSheet.html
index 3f44f19706d9..1d7aa070363b 100644
--- a/layout/style/test/test_addSheet.html
+++ b/layout/style/test/test_addSheet.html
@@ -12,7 +12,7 @@
 <iframe id="iframe2" src="additional_sheets_helper.html"></iframe>
 
 <pre id="test">
-<script type="application/javascript; version=1.8">
+<script type="application/javascript">
 
 let gIOService = SpecialPowers.Cc["@mozilla.org/network/io-service;1"]
   .getService(SpecialPowers.Ci.nsIIOService);
diff --git a/layout/style/test/test_additional_sheets.html b/layout/style/test/test_additional_sheets.html
index 9ca5fa7690cd..5c933a67c75e 100644
--- a/layout/style/test/test_additional_sheets.html
+++ b/layout/style/test/test_additional_sheets.html
@@ -9,7 +9,7 @@
 <a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=737003">Mozilla Bug 737003</a>
 <iframe id="iframe" src="additional_sheets_helper.html"></iframe>
 <pre id="test">
-<script type="application/javascript; version=1.8">
+<script type="application/javascript">
 
 var gIOService = SpecialPowers.Cc["@mozilla.org/network/io-service;1"]
   .getService(SpecialPowers.Ci.nsIIOService)
diff --git a/layout/style/test/test_computed_style_prefs.html b/layout/style/test/test_computed_style_prefs.html
index 163176237cae..2bb8e02f0ecf 100644
--- a/layout/style/test/test_computed_style_prefs.html
+++ b/layout/style/test/test_computed_style_prefs.html
@@ -12,7 +12,7 @@
   
 </div>
 <pre id="test">
-<script type="application/javascript; version=1.7">
+<script type="application/javascript">
 
 /** Test that preffed off properties do not appear in computed style **/
 
diff --git a/layout/style/test/test_media_queries_dynamic.html b/layout/style/test/test_media_queries_dynamic.html
index ac04d803a136..8c7cfe270174 100644
--- a/layout/style/test/test_media_queries_dynamic.html
+++ b/layout/style/test/test_media_queries_dynamic.html
@@ -15,7 +15,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=473400
   
 </div>
 <pre id="test">
-<script class="testbody" type="application/javascript; version=1.7">
+<script class="testbody" type="application/javascript">
 
 /** Test for Bug 473400 **/
 
diff --git a/toolkit/components/extensions/test/mochitest/mochitest-common.ini b/toolkit/components/extensions/test/mochitest/mochitest-common.ini
index 6ad08e392408..58442745437f 100644
--- a/toolkit/components/extensions/test/mochitest/mochitest-common.ini
+++ b/toolkit/components/extensions/test/mochitest/mochitest-common.ini
@@ -109,7 +109,6 @@ skip-if = os == 'android' # unsupported.
 [test_ext_idle.html]
 [test_ext_inIncognitoContext_window.html]
 skip-if = os == 'android' # Android does not support multiple windows.
-[test_ext_jsversion.html]
 [test_ext_listener_proxies.html]
 [test_ext_new_tab_processType.html]
 [test_ext_notifications.html]
diff --git a/toolkit/components/extensions/test/mochitest/test_ext_jsversion.html b/toolkit/components/extensions/test/mochitest/test_ext_jsversion.html
deleted file mode 100644
index 18f7252e96e5..000000000000
--- a/toolkit/components/extensions/test/mochitest/test_ext_jsversion.html
+++ /dev/null
@@ -1,71 +0,0 @@
-<!DOCTYPE HTML>
-<html>
-<head>
-  <title>Test for simple WebExtension</title>
-  <meta charset="utf-8">
-  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
-  <script type="text/javascript" src="/tests/SimpleTest/SpawnTask.js"></script>
-  <script type="text/javascript" src="/tests/SimpleTest/ExtensionTestUtils.js"></script>
-  <script type="text/javascript" src="head.js"></script>
-  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
-</head>
-<body>
-
-<script type="text/javascript">
-"use strict";
-
-add_task(async function test_versioned_js() {
-  // We need to deal with escaping the close script tags.
-  // May as well consolidate it into one place.
-  let script = attrs => `<script ${attrs}><\/script>`;
-
-  let extension = ExtensionTestUtils.loadExtension({
-    manifest: {
-      "background": {"page": "background.html"},
-    },
-
-    files: {
-      "background.html": `
-        <meta charset="utf-8">
-        ${script('src="background.js" type="application/javascript"')}
-        ${script('src="background-1.js" type="application/javascript;version=1.8"')}
-        ${script('src="background-2.js" type="application/javascript;version=latest"')}
-        ${script('src="background-3.js" type="application/javascript"')}
-      `,
-
-      "background.js": function() {
-        window.reportResult = msg => {
-          browser.test.assertEq(
-            msg, "background-script-3",
-            "Expected a message only from the unversioned background script.");
-
-          browser.test.sendMessage("finished");
-        };
-      },
-
-      "background-1.js": function() {
-        window.reportResult("background-script-1");
-      },
-      "background-2.js": function() {
-        window.reportResult("background-script-2");
-      },
-      "background-3.js": function() {
-        window.reportResult("background-script-3");
-      },
-    },
-  });
-
-  consoleMonitor.start([{message: /Versioned JavaScript.*not supported in WebExtension.*developer\.mozilla\.org/},
-                        {message: /Versioned JavaScript.*not supported in WebExtension.*developer\.mozilla\.org/}]);
-
-  await Promise.all([extension.startup(),
-                     extension.awaitMessage("finished")]);
-
-  await consoleMonitor.finished();
-  await extension.unload();
-});
-
-</script>
-
-</body>
-</html>
diff --git a/uriloader/exthandler/tests/mochitest/download_page.html b/uriloader/exthandler/tests/mochitest/download_page.html
index f02380f854c5..5837eeabda99 100644
--- a/uriloader/exthandler/tests/mochitest/download_page.html
+++ b/uriloader/exthandler/tests/mochitest/download_page.html
@@ -5,7 +5,7 @@
 <head>
   <meta charset=UTF-8>
   <title>Test page for link clicking</title>
-  <script type="text/javascript; version=1.8">
+  <script type="text/javascript">
     function launch_download() {
       window.open("download.bin", "_blank", "height=100,width=100");
     }
