Use Troubleshoot Mode in Firefox

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  • Creator: scoobidiver
  • Comment: fixed links, removed keyword, drop support for fx35
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Safe Mode is a special Firefox mode that can be used to troubleshoot and fix problems. Safe Mode, temporarily resets some settings and disables add-ons that might be causing problems. By comparing Firefox behavior in normal mode to its behavior in Safe Mode you may be able to pinpoint the cause of the problem.

Note: Windows users may be familiar with a Safe Mode for Windows. Firefox Safe Mode has no connection to Windows Safe Mode.
Note: The Refresh Firefox feature can fix many issues by restoring Firefox to its default state while saving your essential information. Consider using it before going through a lengthy troubleshooting process.

How to start Firefox in Safe Mode

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 (for example /usr/lib/firefox).

Safe Mode window

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You now have three options:

  • Clicking the Exit button cancels your attempt to get into Firefox's Safe Mode.
  • Clicking the Continue in Safe Mode button will temporarily disable your extensions and themes, turn off hardware acceleration and reset toolbar and button customizations. When you leave Safe Mode and start Firefox up normally, your extensions, themes, and settings will return to the state they were in before you entered Safe Mode.
  • The Make Changes and Restart button is only enabled if you select one of the boxes above it. See the Make permanent changes to Firefox in the Safe Mode window section below for more information.

Safe Mode window

Safe Mode Fx 15 - Win

You now have two options:

  • Clicking the Start in Safe Mode button will temporarily disable your extensions and themes, turn off hardware acceleration and reset toolbar and button customizations. When you leave Safe Mode and start Firefox up normally, your extensions, themes, and settings will return to the state they were in before you entered Safe Mode.
  • Clicking the Reset Firefox button will restore Firefox to its factory default state while saving your essential information. See Refresh Firefox - reset add-ons and settings for more information about this option.

Troubleshooting problems in Safe Mode

Once Firefox is in Safe Mode, you'll want to test its behavior and see if the problem goes away.

The problem happens in Safe Mode

If the problem still happens in Safe Mode, it is not being caused by an extension or theme. Other possible causes could be plugins or changes made to Firefox preference settings, which are not disabled in Safe Mode. See the following articles for solution:

The problem does not happen in Safe Mode

If the problem does not happen in Safe Mode, it is most likely because of an extension, theme or hardware acceleration.

Exiting Safe Mode

  1. 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.
  2. Start Firefox as you normally would.

Make permanent changes to Firefox in the Safe Mode window

When you start Firefox in Safe Mode, you can elect to make the following permanent changes by selecting a checkbox and clicking the Make Changes and Restart button.

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Warning: When you make these changes and restart Firefox, they will remain in effect from that point on, unless you take additional steps to undo them. Some changes cannot be undone.
  • Disable all add-ons: If you select this box and then click Make Changes and Restart then Firefox will start back up in its normal mode, except all your extensions, themes and plugins will be disabled (not uninstalled). To undo the change, you will need to enable each extension and plugin listed in the Add-ons Manager. See this article if you need more help enabling your add-ons.
  • Reset toolbars and controls: If you select this box and then click Make Changes and Restart then Firefox will start back up in its normal mode except any toolbar customizations you have made will be lost, such as position of buttons and toolbars. If you later want to undo this change, you will need to add back those customizations. See Customize Firefox controls, buttons and toolbars for more help.
  • Delete all bookmarks except for backups: If you select this box and then click Make Changes and Restart then Firefox will delete your current bookmarks and replace them with the default set. If you later want to undo the change, you will need to restore your bookmarks from backup. See Restore bookmarks from backup or move them to another computer for more help.
  • Reset all user preferences to Firefox defaults: If you select this box and then click Make Changes and Restart then changes you have made to Firefox options and preferences will be set back to the default settings. This change will be hard to undo, since you may not remember all of the settings you have changed.
  • Restore default search engines: If you select this box and then click Make Changes and Restart then any of the default search engines you deleted will be restored. This does not remove any added search engines. To undo this change, simply go to the Search Bar and remove the search engines you don't want.




Based on information from Safe mode (mozillaZine KB)