Firefox may give you a "Warning: Unresponsive script" prompt that says "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete." This article describes why this could happen and possible solutions and workarounds.

This error is telling you that Firefox thinks that a script may be running out of control and would make Firefox hang if nothing is done. The script could be something on a web page you're accessing, in an extension you installed, or even Firefox itself.

Table Of Contents

• Webroot Spy Sweeper
• Letting the script run longer
• Error happens when accessing certain web sites
• Other causes

Webroot Spy Sweeper

Webroot Spy Sweeper can cause this problem. Disabling Spy Sweeper's Tracking Cookies feature (or disabling Spy Sweeper altogether) can solve the issue.

Letting the script run longer

If you find that pressing the Continue button brings up the same dialog again, letting the script run longer won't help you; it will just make Firefox hang for longer. However, if you can use Firefox normally after pressing Continue, then the script may just needs extra time to complete.

To tell Firefox to let the script run longer:

1. In the Location bar, type about:config, and press EnterReturn.
   • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
2. In the about:config page, search for the preference dom.max_script_run_time, and double-click on it.
3. In the Enter integer value prompt, type 20.
4. Press OK.

With scripts now allowed to run for longer times, you may no longer receive the prompt.

If you still receive the prompt, you should set that preference back to the default value.

1. In the Location bar, type about:config, and press EnterReturn.
   • The about:config "This might void your warranty!" warning page may appear. Click I'll be careful, I promise!, to continue to the about:config page.
2. In the about:config page, search for the preference dom.max_script_run_time.
3. Right-clickHold down the Ctrl key while you click on it and choose Reset.

Error happens when accessing certain web sites

If the error happens only on a specific web site, you can block scripts from running on that web site. Many sites still function even if scripting is disabled.

1. Install the YesScript extension and restart Firefox.
2. At the Open the Firefox windowOn the menu bar, click the Tools menu and select Add-ons.
3. In the dialog that comes up, click on the YesScript entry.
4. Click OptionsPreferences.
5. In the YesScript Blacklist dialog, type the URL of the site that's giving you problems in the text box.
6. Click Add. The domain name of the site will be added to the list.

Now that the problematic site has been blocked from running scripts, it will no longer cause unresponsive script warnings.

Other causes

An add-on could be causing the problem. See Troubleshooting extensions and themes.

Based on information from Unresponsive Script Warning (mozillaZine KB)