Resetting preferences (zoom, tabs, privacy, network, encryption, updates, where to save file downloads, etc.) is one of many procedures that can be helpful in troubleshooting Firefox problems. We'll explain two ways to do this.

• If changes to preference settings are not saved when you restart Firefox, see How to fix preferences that won't save.

Solution 1: Refresh Firefox

1. Click the menu button and then click help .
2. From the Help menu choose Troubleshooting Information.

   If you're unable to access the Help menu, type about:support in your address bar to bring up the Troubleshooting Information page.

3. Click the Refresh Firefox button in the upper-right corner of the Troubleshooting Information page.

   

4. To continue, click Refresh Firefox in the confirmation window that opens.
5. Firefox will close to refresh itself. When finished, a window will list your imported information. Click Finish and Firefox will open.

Solution 2: Delete Firefox preference files

1. Click the menu button , click help and select Troubleshooting Information. The Troubleshooting Information tab will open.

2. Under the Application Basics section, click on Show FolderOpen FolderShow in FinderOpen Directory. A window with your profile filesfolder will open.
Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.
3. Click the menu button and then click ExitQuit .
4. Locate and delete the file prefs.js (or rename it, for example, to prefs.jsOLD, to keep the old file as a backup). If you find more than one, a prefs.js.moztmp file or a user.js file, delete (or rename) these as well.
5. You can close the profile folder and open Firefox now.