Safe Mode

Safe Mode is a special Firefox execution mode that can be used to troubleshoot issues in Firefox. In Safe Mode, you can reset some settings or disable add-ons that might be the source of the issue. By comparing Firefox behavior in normal mode to its behavior in Safe Mode, where various items are disabled, you may be able to diagnose issues.

Note: Windows users may be familiar with a Safe Mode for Windows. Firefox Safe Mode has no connection to Windows Safe Mode.

How to start Firefox in Safe Mode

At the top of the Firefox windowOn the menu bar, click the Help menuFirefox button, go over to the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.
For Windows XP, 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-4)
At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click 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 QuitAt the top of the Firefox window, click on the File menu and 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. Then in Windows, click Start, open the All Programs list and navigate to the Mozilla Firefox folder. In the Mozilla Firefox folder, select Mozilla Firefox (Safe Mode).Then hold down the option key as you restart Firefox.Go to your Terminal and run: firefox -safe-mode
You may need to specify the Firefox installation path (e.g. /usr/lib/firefox-3.5). Firefox will start up with the Firefox Safe Mode dialog.
Note: You can also start Firefox in Safe Mode by clicking Start, selecting Run (or use the Start Search box in Windows 7 and Vista) and then entering the following in the text field: firefox -safe-mode


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 starts Firefox in its Safe Mode. While you are in Safe Mode, your extensions and themes will be disabled, and any toolbar customizations will be reverted back to their defaults. These changes are temporary - 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.

You can elect to make the following changes:

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 How do I customize the 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 (this item is labeled Reset bookmarks to Firefox defaults in Firefox 3.5). If you later want to undo the change, you will need to restore your bookmarks from backup. See Backing up and restoring bookmarks 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. To undo this change, simply go to the Search bar and remove the search engines you don't want.


Exiting Safe Mode

  1. At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click 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 QuitAt the top of the Firefox window, click on the File menu and 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.
  2. Start Firefox as you normally would.





Based on information from Safe mode (mozillaZine KB)

Contributors to this page: AliceWyman, Bo102010, zzxc, Tonnes, scoobidiver, jack013

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