Userscripts not working in Chrome? Turn on Allow User Scripts

You install a userscript manager, add a script, open the page, and nothing happens. No error, no warning. The script is listed and switched on, and the page looks exactly as it did.

In current versions of Chrome, the most common reason is a single setting.

Why Chrome asks

Under Manifest V3, an extension may only run code that ships inside it, and Chrome reviews that code before it reaches you. A userscript is, by definition, code you add afterwards. Chrome's answer is a special userScripts API that lets an extension run scripts you supply, but only once you've allowed it for that extension.

Until you do, the manager is installed and working, and Chrome simply doesn't let it run your scripts.

Chrome 138 and later: Allow User Scripts

According to Chrome's extension documentation, as of October 2026:

1. Open chrome://extensions in a new tab.
2. Find your userscript manager and click Details.
3. Turn on Allow User Scripts.
4. Reload the page your script is meant to change.

The switch belongs to each extension, so if you use two managers, turn it on for both.

Tampermonkey's own instructions offer a shortcut to the same page: right-click its toolbar icon and choose Manage Extension.

Before Chrome 138: Developer mode

Older versions of Chrome had no separate switch. Instead:

1. Open chrome://extensions.
2. Turn on Developer mode with the toggle at the top right.
3. Reload the page.

To see which version you have, open chrome://settings/help. If an update is waiting, it's worth taking it, and then using the switch above.

Microsoft Edge

Edge is built on the same engine. Tampermonkey's instructions give the same switch on the extension's details page in current versions, and Developer mode at edge://extensions otherwise.

If it still does nothing

Once the switch is on, work through these in order:

• Is the script switched on in the manager? Most managers let you turn scripts off one at a time.
• Does its @match line cover this page? A script for https://example.com/* won't run on https://www.example.com/. If you write scripts, the @match tester shows which addresses a pattern covers.
• Has the site changed? A script that looks for a part of the page by its old name finds nothing after a redesign, and does nothing.
• Is the extension allowed on this site? On the same details page, Site access should allow the sites your scripts run on.

For ScriptPanda

ScriptPanda runs the tools it builds as userscripts too, so it needs the same switch: chrome://extensions, then ScriptPanda, then Details, then Allow User Scripts. Setup walks you to that page, and ScriptPanda needs Chrome 138 or later.

If you're new to all this, What is a userscript? explains what the switch is allowing, and ScriptPanda vs Tampermonkey covers which kind of tool fits what you want to do.

The short version

Scripts that install but never run usually mean Chrome hasn't been told to allow them. Open chrome://extensions, click Details on your manager, and turn on Allow User Scripts. On a Chrome older than 138, turn on Developer mode instead.