Reset Firefox preferences to troubleshoot and fix problems

Revision Information
  • Revision id: 36935
  • Created:
  • Creator: Michael Verdi
  • Comment: Based on Jan's revision and incorporating suggestion in https://support.mozilla.org/en-US/kb/reset-preferences-fix-problems/discuss/2462
  • Reviewed: Yes
  • Reviewed:
  • Reviewed by: Verdi
  • Is approved? Yes
  • Is current revision? No
  • Ready for localization: No
Revision Source
Revision Content

When troubleshooting Firefox problems, resetting preferences (zoom, tabs, privacy, network, encryption, download actions, etc.) is one of many procedures that can be helpful in pinpointing the issue. This article explains how to use Safe Mode to reset preferences.

To reset preferences:

Click the menu button Fx89menuButton, click Help, select Troubleshoot Mode… and click Restart in the Restart Firefox in Troubleshoot Mode? dialog.

Note: You can also start Firefox in Troubleshoot 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. Click to put a check mark by Reset all user preferences to Firefox defaults.

    89a0533be70261469542ad18a5b0fa00-1259976432-945-1.png


    89a0533be70261469542ad18a5b0fa00-1256947708-467-1.png
  2. To apply your changes, click Make Changes and Restart.

Firefox will restart with your preference settings changed back to the defaults.

Resetting preferences (zoom, tabs, privacy, network, encryption, download actions, etc.) is one of many procedures that can be helpful in fixing Firefox issues. There are two ways to do this - reset Firefox to it's default state or delete the preference files. We'll explain both methods.

Solution 1: Reset Firefox to it's default state

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 the menu button Fx89menuButton, click Help and select More Troubleshooting Information.
  2. Click Refresh Firefox… then Refresh Firefox in the confirmation window that opens. Firefox will close to refresh itself.
  3. When finished, a window will list your imported information. Click the Finish button. Firefox will open.
  4. Select whether you want Firefox to restore all or some windows and tabs and click the Let's go! button.
Note: There's a Refresh Firefox button in the Firefox Troubleshoot 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.

Solution 2: Delete Firefox preference files

Click the menu button Fx89menuButton, click Help, select Troubleshoot Mode… and click Restart in the Restart Firefox in Troubleshoot Mode? dialog.

Note: You can also start Firefox in Troubleshoot 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. Click to put a check mark by Reset all user preferences to Firefox defaults.

    89a0533be70261469542ad18a5b0fa00-1259976432-945-1.png


    89a0533be70261469542ad18a5b0fa00-1256947708-467-1.png
  2. To apply your changes, click Make Changes and Restart.

Firefox will restart with your preference settings changed back to the defaults.

    • Click the menu button Fx89menuButton, click Help and select More Troubleshooting Information.From the Help menu, select More Troubleshooting Information. The Troubleshooting Information tab will open.
    • Under the Application Basics section next to Profile FolderDirectory, click Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.
    Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.
  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  3. Locate and delete the prefs.js file. If you find more than one, a prefs.js.moztmp file or a user.js file, delete these as well.
  4. You can close the profile folder and open Firefox now.