Troubleshoot and diagnose Firefox problems

Most problems with Firefox can be fixed by following the troubleshooting methods described below. Try these steps in order. If one doesn't work, move on to the next one. If you need extra help with any of this, we have a community of volunteers standing by.

1. Restart your computer

Sometimes problems can be fixed by simply restarting your computer and then starting Firefox again.

2. Clear your cookies and cache

Many problems with loading web pages can be resolved by clearing Firefox's cookies and cache:

  1. Click the Library button 57 library icon on your toolbar. (If you don't see it there, click the menu button fx57menu then click Library.) Click History and select Clear Recent History….
  2. In the Time Range to clear: drop-down, select Everything.
  3. Below the drop-down menu, select both Cookies and Cache. Make sure other items you want to keep are not selected.
  4. Click Clear Now.
For more information, see Delete browsing, search and download history on Firefox.

3. Restart Firefox in Safe Mode

Firefox Safe Mode is a troubleshooting mode that disables extensions, uses the default theme, turns off hardware acceleration and uses default toolbar settings, among other changes (see this article for details). To start Firefox in Safe Mode:

  1. Click the menu button Fx57menu, click Help and select Restart with Add-ons Disabled…. Firefox will start up with the Firefox Safe Mode dialog.
    Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.holding down the option key while starting Firefox.quitting Firefox and then going to your Terminal and running: firefox -safe-mode
    You may need to specify the Firefox installation path (e.g. /usr/lib/firefox)
  2. In the Firefox Safe Mode dialog, click Start in Safe Mode.
  3. Check whether your problem is still happening while in Safe Mode.
  • If the problem still happens in Safe Mode, go on to step 4.
  • If the problem does not happen in Safe Mode, see Turn content blocking off on individual sites, if certain websites only work correctly while in Firefox Safe Mode. For other issues, follow these instructions to troubleshoot extensions, themes and hardware acceleration.

4. Reinstall Firefox

Some Firefox issues can be caused by a problem with one of the Firefox program files. Follow these steps to completely remove and reinstall Firefox. This process will not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

Note: You might want to print these steps or view them in another browser.
  1. Download and save the installer for the latest official version of Firefox from
  2. Exit Firefox (if open): Click the Firefox menu Fx57Menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx57Menu and select Quit.
  3. You may want to make a note of the Mozilla Firefox program folder location (right-click the Firefox desktop icon, select Properties from the context menu and click the Shortcut tab) since there may be leftover files and folders after you uninstall Firefox that should be removed for a clean reinstallation.
  4. Uninstall Firefox from your computer.
  5. Delete the Firefox program folder, which is normally found in one of these locations by default:
    • C:\Program Files\Mozilla Firefox
    • C:\Program Files (x86)\Mozilla Firefox
  6. Reinstall Firefox using the installer you downloaded earlier - see How to download and install Firefox on Windows for instructions.
  1. Download the latest official version of Firefox from
  2. Quit Firefox: Click the Firefox menu Fx57Menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx57Menu and select Quit.
  3. Uninstall Firefox from your computer by opening the Applications folder in the Finder and dragging the Firefox application to the Trash.
  4. Reinstall Firefox - see How to download and install Firefox on Mac for instructions.
  1. Download the latest official version of Firefox from
  2. Quit Firefox: Click the Firefox menu Fx57Menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx57Menu and select Quit.
  3. Uninstall Firefox - If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux for details. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory to uninstall Firefox.
  4. Reinstall Firefox - see Install Firefox on Linux for instructions.

Now start Firefox and check to see if your problem has been fixed. If it hasn't, continue with the next troubleshooting method.

5. Refresh Firefox

The Refresh Firefox feature can fix many issues by restoring your Firefox profile to its default state while saving your essential information.
If you have many Firefox customizations, you may want to skip this step and create a new Firefox profile instead (see step 6, below) so that your old profile is easily recoverable from the Profile Manager.

Note: When you refresh Firefox, your bookmarks, browsing history, open tabs, windows, passwords, cookies and web form auto-fill information will be saved. However, your extensions and themes will be removed and your preferences will be reset. Learn more.
  1. Click this Refresh Firefox button directly, if you are viewing this page in Firefox. This won't work if you are using a different browser or a mobile device.
  2. To continue, click Refresh Firefox in the confirmation window that opens.
  3. Firefox will close to refresh itself. When finished, a window will list your imported information. Click Finish and Firefox will open.

Note: There's a Refresh Firefox button in the Firefox Safe Mode window, if you can't start Firefox normally. You can also do a manual refresh by creating a new profile and transferring your important data to the new profile.

6. Create a new Firefox profile

Sometimes files in your Firefox profile folder that correspond to the essential information that a Firefox Refresh doesn't remove (such as bookmarks and browsing history) may be causing the issue. You can create a new, additional profile which will not contain any of your old Firefox data. See the Profile Manager - Create, remove, or switch Firefox profiles article for instructions.

Other solutions

If you've tried all of these troubleshooting methods, and you're still having problems, here are some other solutions you can try:

Check browser internals

The Firefox Task Manager (about:performance page) lets you see what tabs or extensions are slowing down Firefox. Telemetry Data shared with Mozilla (about:telemetry page) contains detailed data about performance, hardware, usage and customization. The Troubleshooting Information page (about:support page) includes other about: page links and troubleshooting resources. (For a list of all about: pages, enter about:about in the address bar.)

Troubleshoot the Flash plugin

See Flash Plugin - Keep it up to date and troubleshoot problems.

End of Flash support: Like other browsers and Adobe, Firefox ended Flash support at the end of 2020. Please see End of support for Adobe Flash for more information.

Check for conflicts with your Internet security software

Some Internet security software (including antivirus, antispyware, and firewall programs) can cause problems with Firefox including blocking it from opening websites, crashes, and more. Often you can open the program's settings, remove Firefox from its list of allowed or trusted programs, and it will be re-detected and things should start working again. If your program is listed at the Configure firewalls so that Firefox can access the Internet article, you can get specific instructions for how to properly reconfigure it.

Check for malware

Malware (short for "malicious software") can cause problems with Firefox. Periodically, you should scan your system for viruses, spyware, or other malware. For more information, see Troubleshoot Firefox issues caused by malware.

Based on information from Standard diagnostic - Firefox (mozillaZine KB)

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