Troubleshoot and diagnose Firefox problems

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Many common problems with Firefox can be resolved with some of the troubleshooting steps described below.


Standard troubleshooting steps

Take the following steps in order if you are experiencing a problem with Firefox. If one doesn't work, try the next one.

Restart Firefox

Close Firefox completely:

At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

Click the menu button New Fx Menu and then click ExitQuit Close 29 .

Then restart your computer and start Firefox again.

Clear private data

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

  1. Click on the Tools menu and select Clear Private Data... to bring up the Clear Private Data window.
  2. Select the following items in the list, and then press Clear Private Data Now:
  • Download History
  • Cache
  • Cookies

For more information, see Clearing private data.

Clear cookies and cache

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

  1. Click on the Tools menu and select Clear Recent History... to bring up the Clear Recent History window
  2. In the Time range to clear drop-down menu, select Everything
  3. Click the arrow next to Details to display the list of items to clear, then select the following items:
    • Cache
    • Cookies
  1. Click Clear Now.

For more information, see Delete browsing, search and download history on Firefox.

Troubleshoot extensions and themes

Sometimes add-ons for Firefox (extensions or themes) can cause problems. To confirm whether your problem is caused by an add-on, launch Firefox's Troubleshoot Firefox issues using Safe Mode:

At the top of the Firefox window, click the Firefox button, go over to the Help menuOn the menu bar, click the Help menuAt the top of the Firefox window, click the Help menu 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)
Click the menu button New Fx Menu , click help Help-29 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)

  1. In the Firefox Safe Mode dialog, click Continue in Safe Mode.
  2. Test for your problem.

If the problem does not occur in Safe Mode, an extension or theme is likely the cause. For more information about troubleshooting extensions and themes, and how to narrow down which add-on is causing problems, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems.

Reset preferences

If the problem was not fixed by disabling add-ons, you may need to revert changes you've made to Firefox's configuration:

At the top of the Firefox window, click the Firefox button, go over to the Help menuOn the menu bar, click the Help menuAt the top of the Firefox window, click the Help menu 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)
Click the menu button New Fx Menu , click help Help-29 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)

  1. In the Firefox Safe Mode dialog, click to put a check mark by Reset all user preferences to Firefox defaults and Reset toolbars and controls.
  2. To apply your changes, click Make Changes and Restart.

Troubleshoot plugins

Sometimes plugins for Firefox (such as Adobe Reader, Flash, Java, QuickTime, RealPlayer, and Windows Media Player) can cause problems.

  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. Click each plugin in the list and then click Disable.
  4. Test for your problem.

For more information about various plugins, and what to do if you find the plugin that causes problems, see the Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems article.

Further troubleshooting steps

If the steps above don't fix your problem, continue by following these instructions.

Make 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 - see Starting the Profile Manager for instructions.
  2. Create a new profile - see Creating a profile for instructions.
  3. Click on the newly created profile in the Profile Manager and click Start Firefox.

Test to see if your problem occurs with the new profile. If it doesn't, you can copy your data to the new profile - see Recovering important data from an old profile for instructions. For troubleshooting purposes, only copy the files that correspond to your bookmarks and saved passwords.

Clean reinstall

Some Firefox issues can be resolved by downloading a new Firefox installer from Mozilla.com, then closing Firefox, deleting the Firefox application folder (program files) and reinstalling Firefox. If this does not help, or if you would rather completely remove Firefox and start over instead of completing all the troubleshooting steps, follow these steps:

  1. Download the latest official version of Firefox from Mozilla.com.
    • You should avoid unofficial download sites that bundle Firefox with other software such as the Google Toolbar.
  1. If you wish to retain your current profile, you should make a backup copy of it. See Back up and restore information in Firefox profiles for instructions.
  2. Uninstall Firefox and make sure you remove the Firefox application (program) folder and your Firefox personal data (user data and settings) - see Uninstall Firefox from your computer for instructions.
  3. Reinstall Firefox - see Installing Firefox for instructions.
  4. When Firefox is started for the first time, the Import Wizard will appear and a new profile will be created.
  5. Verify that the issue no longer appears.
  6. If you made a backup of your old profile and wish to restore your old information, see Recovering important data from an old profile. For troubleshooting purposes, only copy the files corresponding to your bookmarks and saved passwords.
  7. Reinstall your extensions and themes one by one to determine if any specific one is causing the issue.

Other solutions

If you've tried the above steps, including a clean reinstall, the following solutions may help to resolve your problem.

Note: This section does not contain step-by-step instructions. For more information on any of these solutions, please consult the appropriate documentation that came with your operating system or other software product.

Internet security software

Some Internet security software (including antivirus, antispyware, and firewall programs) can cause problems with Firefox. These can include limited ability to open pages, crashes, and more.

If you are using firewall or other Internet security software, verify that the Firefox application is not block from communicating with the Internet.

Most of the time you can open a program's settings, remove Firefox from its list of allowed or trusted programs, and then let it re-detect Firefox, and things will start working again. This step is worth repeating, even if you've not had problems with your Internet security software before. 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.

Viruses and Spyware.

Periodically, you should scan your system for viruses, spyware, or other malware. One of the following free services may be useful for virus scans:

Some malware programs may target the Firefox application file. The following instructions may help diagnose such a problem:

  1. At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.

    Click the menu button New Fx Menu and then click ExitQuit Close 29 .

  2. Open the Firefox application folder - by default, it is:
    C:\Program Files\Mozilla Firefox.
  3. Rename firefox.exe to firefox1.exe.
  4. Double-click firefox1.exe to launch Firefox.
  5. If Firefox runs without problems, some malicious code may be targeting Firefox (firefox.exe). Scan your computer for malicious code using the links above or your own antivirus or antispyware program.

It's also possible that an ad-blocker, web-accelerator, antivirus or other running program is conflicting with Firefox. Try temporarily disabling these other programs one at a time.

File system errors

If your computer's file system has a problem, that may prevent Firefox from running. Run the error-checking tool Chkdsk on your drive to look for and repair errors.

For more help

If after following the steps above, you still have problems with Firefox:



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