How to Troubleshoot Firefox

When Firefox misbehaves, there's usually an easy fix

Last Updated: February 11, 2022 Tested

Many problems with Firefox are caused by faulty extensions or themes, incorrect settings, or corrupt files. If Firefox does not work properly (or not at all), don't panic! This step-by-step guide will help you troubleshoot problems with Firefox.

Method 1

Method 1 of 7:

Restart Firefox

1
Open the "File" menu, or Firefox Menu then select "Quit Firefox" (do not use the close button on the upper-right corner of the window). If Firefox continues to work improperly, repeat this step and restart your computer.

Method 2

Method 2 of 7:

Clear Firefox Cache

1
Many problems with loading web pages can be resolved by clearing Firefox's cookies and cache. Open the "Tools" menu, then select "Clear Private Data". Select the following items, then click "Clear Private Data Now":
- Download History
- Cache
- Cookies

Method 3

Method 3 of 7:

Use Firefox's Safe Mode

1
Sometimes add-ons for Firefox (extensions or themes) can cause problems. Safe Mode runs Firefox with your add-ons disabled. Follow these steps to start Safe Mode:
2
Make sure Firefox is closed (open the "File" menu, then select "Exit")
3
Click the Start button, open the All Programs list, and navigate to the Mozilla Firefox folder. Select "Mozilla Firefox (Safe Mode)".
4
When the Safe Mode dialog box appears, click "Continue in Safe Mode"
5
If the problem does not occur in Safe Mode, and extension or theme is likely the cause. Read the Troubleshooting Extensions and Themes article on the Firefox Support website for more information.

Method 4

Method 4 of 7:

Reset Firefox Preferences

Incorrect settings can cause problems. You can restore Firefox's default settings by following these steps:

1
Close down Firefox completely (open the "File" menu, then select "Exit")
2
Click the Start button, open the All Programs list, and navigate to the Mozilla Firefox folder. Select "Mozilla Firefox (Safe Mode)".
3
When the Safe Mode dialog box appears, put a check mark by "Reset all user preferences to Firefox defaults" and "Reset toolbars and controls"
4
Click "Make Changes and Restart"

Method 5

Method 5 of 7:

Troubleshoot Plugins

Sometimes plugins for Firefox (such as Adobe Reader, Flash, Java, QuickTime, RealPlayer, and Windows Media Player) can cause problems. Safe Mode does not disable plugins, but they can be disabled while Firefox is running.

1
Open the Add-ons Window by clicking the "Tools" menu and selecting "Add-ons"
2
Click on the Plugins icon at the top of the Add-ons window
3
Disable each plugin one-by-one until the problem goes away. You do not have to restart Firefox each time.
4
If you encounter a plugin that is causing problems, you may need to update or reinstall it. If the problem continues, you can leave the plugin disabled.

Method 6

Method 6 of 7:

Create a New Profile

A corrupt profile can cause various problems with Firefox. You can try to make a new profile test whether that solves the problem, and if so, copy your data (bookmarks, saved passwords, etc.) to the new profile.

1
Start the Profile Manager
2
Create a new profile
3
Select the newly created profile and click "Start Firefox"
4
If the problem goes away, you can recover your important data. To avoid recreating the problem, only recover important files such as your bookmarks and saved passwords.

Method 7

Method 7 of 7:

Reinstall Firefox

If creating a new profile does not solve the problem, you will need to reinstall Firefox.

1
Make sure Firefox is closed (open the "File" menu, then select "Exit")
2
Download the latest version of Firefox from mozilla.com
3
Back up your important data if you wish to do so
4
Uninstall Firefox using the Add/Remove Programs utility in the Windows Control Panel
5
Delete the "Mozilla Firefox" folder located in the Windows "Program Files" folder
6
Delete the Firefox profile folder
7
Run the Firefox installation program
8
When Firefox is started for the first time, the "Import Settings and Data" wizard will appear and a new profile will be created
9
Recover your important data if you chose to do so
10
Reinstall your extensions and themes

Community Q&A

Question

Firefox keeps running, and I can't stop it with End Task. What do I do?

Community Answer

If you're using a Mac, try command Q -- keep hitting that until it's forced to work.
Question

I cannot delete or move bookmarks. What should I do?

Community Answer

Broken bookmarks is caused by Firefox profile corruption, and the proper fix is to create a new profile. First, export bookmarks somewhere safe to import into the new profile, and if there are any cookies or passwords needed, I'd save those files following the above link for "Recovering important data from an old profile" (links not allowed). Then it's simply a matter of creating a new profile, which takes seconds if you start Firefox from the command line using "firefox.exe -p" either from the program folder or temporarily modifying the "target" line in the Firefox shortcut icon by right click > properties and adding " -p" to the end to start Firefox in the profile manager.