An unresponsive script warning is a browser message that appears when JavaScript code on a web page or add-on takes too long to run. The message may look like the example below.

Warning: Unresponsive script. A script on this page may be busy or may have stopped responding.

You have the choice of “Stop Script” or “Continue” buttons. Click the “Stop Script” button to stop the script from running. Stopping the script can prevent the browser from running out of memory or crashing.

If this problem is only happening on one page and every other page is fine, a script on that one page is likely causing your problem. Unless you’re the Webmaster of that page, there is nothing you can do to prevent this error. If this error is happening on different websites, it may be an issue with your computer or a browser add-on.

To identify the script/add-on that is causing the problem, you can try one of the following procedures.

Open the Browser Console

For a script in the web page, you can open the Firefox Browser Console, which may show what is causing the error. To open the error console, press the Alt key to view the file menu, then select Tools, Web Developer, and Browser Console, or press Ctrl+Shift+J.

Identifying a script or add-on issue often requires more technical expertise about scripts and add-ons. There is usually no “easy” fix to resolve this type of error.

In the Browser Console, look for references to a specific script or add-on that generated the error message. If you find a reference to an add-on that generated the error, you can disable the add-on to see if that resolves the error.

  • How to disable or remove browser extensions.

Disable add-ons or run the browser in Safe Mode

To see what add-on may be causing a problem, you can disable an individual add-on and see if the error persists. If so, then you can enable that add-on again and try disabling another.

Each script or add-on error can differ in terms of what is displayed in the Browser Console, so there’s not one specific thing we can recommend trying to find.

Another option is to open Firefox in Safe Mode, which disables all add-ons. If you have no problems in Safe Mode, you can safely assume it’s one of your add-ons causing the error.

  • How to disable or remove browser extensions.
  • How to open a browser in Safe Mode.

Debug error in script

If you’re the Webmaster or developer of the script causing the browser error, you can try to resolve this error. Review the possible causes to this error below for help on debugging the script.

  • Error in a script that prevents the script or related script from successfully executing.
  • Any loops in the script that don’t exist.
  • Any script or script data loading from a source that is not available.
  • Conflict between your script and browser add-ons.
  • See our JavaScript and script definition for further information and related links.
  • Internet help and support.