Some problems users experience with Firefox are caused by extensions or themes. This article describes how to determine whether an extension or theme is causing a problem in Firefox, and if it is, how to make Firefox run normally again.

Table Of Contents

• Determining if an extension or theme is the problem
• Updating your themes
• Updating your extensions
• Disabling faulty extensions
• If you have a large number of extensions

Determining if an extension or theme is the problem

Starting Firefox in Safe Mode will show you whether a theme or one of your extensions is causing the problem. In Safe Mode, all your extensions will be temporarily disabled and the default theme is used.

1. Close down Firefox completely: At the top of the Firefox window, click the File menu, and select the Exit menu item.Close down Firefox completely: On the menu bar, click the Firefox menu, and select the Quit Firefox menu item.Close down Firefox completely: At the top of the Firefox window, click the File menu, and select the Quit menu item.
2. In Windows, click Start, open the All Programs list, and navigate to the Mozilla Firefox folder. In the Mozilla Firefox folder, select Mozilla Firefox (Safe Mode).Go to the Utilities directory (in the Applications folder) and open Terminal, then run:

   /Applications/Firefox.app/Contents/MacOS/firefox -safe-mode

   Go to your Terminal and run:

   /path/to/firefox/firefox -safe-mode

3. Firefox should start up with a Firefox Safe Mode dialog.
   
   Note: You can also start Firefox in Safe Mode by clicking Start, selecting Run (or use the Start Search box in Windows Vista) and then entering the following in the text field:
   

   firefox -safe-mode

When the Firefox Safe Mode window appears, press the button Continue in Safe Mode.

If the problem persists in Safe Mode, your problem is not being caused by an extension or theme.

If the problem is not present in Safe Mode, either the theme you are using or one of your extensions may be causing the problem.

If you have been using a new theme, switch to the default theme and restart Firefox to see if the theme was causing the problem.

1. Click on the Tools menu, and select Add-ons. The Add-ons window will appear.
2. In the Add-ons window, click the Themes icon.
3. Select the default theme, then click the Use Theme button, to make Firefox switch to that theme.
4. Close Firefox, then start it up again.

When Firefox restarts, the default theme is in use. If the problem goes away, your theme was causing the problem.

Updating your themes

If an installed theme was causing the problem, it may have an update available that will fix it.

1. Click on the Tools menu and then choose Add-ons. The Add-ons dialog appears.
2. Click the Themes panel, which displays the list of installed themes.
3. To check for updates for installed themes, click Find Updates.
4. If updates are found, install them by clicking Install Updates.
5. When the installation is complete, click Restart Firefox.
6. After Firefox restarts, your themes should have been updated.

Updating your extensions

If the problem persists with the default theme in use, you need to troubleshoot your extensions. If an extension is causing the problem may have an update available that will fix it.

1. Click the Tools menu and then choose Add-ons. The Add-ons dialog appears.
2. Click the Extensions panel, which displays the list of installed extensions.
3. To check for updates to each installed extension, click Find Updates.
4. If updates are found, install them by clicking Install Updates.
5. When the installation is complete, click Restart Firefox.
6. After Firefox restarts, your extensions should have been updated.

Disabling faulty extensions

If there were no updates or if the problem didn't go away after the update, you can individually disable extensions. You won't lose any settings when you disable extensions, and you can re-enable them later.

1. Click the Tools menu and then select Add-ons. The Add-ons dialog appears.
2. Click the Extensions panel. The list of installed extensions is displayed.
3. Click the name of the extension you wish to disable.
4. To disable the selected extension, click Disable.
5. From the menu at the top of the Firefox windowbar, select FileFirefox and then select the ExitQuit FirefoxQuit menu item.
6. Restart Firefox. Now that the extension you chose has been disabled, your problem may be gone.
   • If the problem persists, you should repeat the above process with each extension.

When your problem goes away, the extension that you most recently disabled is the source of the issue. You can then re-enable all the other extensions. You can also look for help from the extension's author by asking him a question on addons.mozilla.org.

Note: Do not re-enable any extensions until you have found the extension causing the problem.

If you have a large number of extensions

If you have a large number of extensions installed then disabling them one by one may take a significant length of time. Disable one half of your extensions to see if the problem still exists:

• If it does, then you know the problem exists in the second half, so you disable half of the remaining enabled extensions, and test again.
• If it doesn't, then you know the problem exists in the first half, so you re-enable half of the extensions we just disabled and test again.

By recursively enabling or disabling extensions in this manner you can home in on a misbehaving extension quicker than disabling them one by one.