Safe Mode

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==External links== ==External links==
-*[ Safe Mode (Firefox Support)]+*[ Safe Mode] (Firefox Support)
===Related bug reports=== ===Related bug reports===

Revision as of 02:39, 30 December 2011

Safe Mode is a debugging startup mode available in Firefox, Thunderbird, and SeaMonkey 2, where all added extensions are disabled, the default theme is used, and default localstore settings (toolbar settings and controls) are used. Also disabled are the Just-in-time (JIT) JavaScript compiler, any changes made via userContent.css and userChrome.css and hardware acceleration. Any changes made to preference settings are unaffected and all available plugins are used in Safe Mode.

Safe Mode in Firefox and SeaMonkey 2 also includes a number of troubleshooting options that allow you to make changes upon browser restart, such as disabling all add-ons or resetting preferences. (see below).


Starting Safe Mode

All systems

  • In current versions of Firefox, Thunderbird, and SeaMonkey 2, you can restart in Safe Mode via "Help -> Restart with Add-ons disabled...". A Safe Mode options window will appear when they restart (see below). [1] [2]

To enter Safe Mode in previous versions (or if you can't open your Mozilla application to use the Help menu) you must first make sure Firefox/Thunderbird/SeaMonkey is not running in the background (including all windows like the Download Manager that open in a separate window) before following the instructions given below.


Use one of these methods to start your Mozilla application in Safe Mode. This should not be confused with restarting the computer in Windows Safe Mode!

  • In current Mozilla application versions, hold down the Shift key while double-clicking the Firefox/Thunderbird/SeaMonkey icon. (If the Profile Manager opens, select a profile and then hold down the Shift key again while clicking the "Start Firefox" button.) [3] [4]
  • In older versions, use the "Mozilla Firefox (Safe Mode)", "SeaMonkey (Safe Mode)", "Mozilla Thunderbird (Safe Mode)", or "Mozilla Thunderbird (No Extensions)" shortcut in the Mozilla Firefox, SeaMonkey, or Mozilla Thunderbird program folder on the Windows Start Menu.

As an alternative method, select "Start -> Run" (on Windows 7/Vista, enable the Run box, as described here) and enter the following in the Windows Run box:

For Firefox, one of these:

  • firefox -safe-mode
  • "C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode
  • "C:\Program Files (x86)\Mozilla Firefox\firefox.exe" -safe-mode

For Thunderbird, one of these:

  • thunderbird -safe-mode
  • "C:\Program Files\Mozilla Thunderbird\thunderbird.exe" -safe-mode
  • "C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe" -safe-mode

For SeaMonkey, one of these:

  • seamonkey -safe-mode
  • "C:\Program Files\SeaMonkey\seamonkey.exe" -safe-mode
  • "C:\Program Files (x86)\SeaMonkey\seamonkey.exe" -safe-mode

Adjust the path accordingly based on the actual installation directory (e.g., on 64-bit Windows, use "Program Files (x86)" instead of "Program Files") or if you installed your Mozilla program in a different location than shown above.


On Linux, you can go to your Terminal and run (for Firefox):

  • /path/to/firefox/firefox -safe-mode

Mac OS X

Hold down the Option key while starting your Mozilla application. (If the Profile Manager opens, select a profile and then hold down the Option key again while clicking the button to start Firefox, Thunderbird, or SeaMonkey.) [5]

As an alternate method, go to Utilities (in the Applications folder) and open Terminal, then run:

For Firefox:

  • /Applications/ -safe-mode

For Thunderbird:

  • /Applications/ -safe-mode

For SeaMonkey:

  • /Applications/ -safe-mode

If you have installed the application to another location, modify the path as such. It's the "-safe-mode" command line parameter that's crucial here.

How to know you are in Safe Mode

Thunderbird and SeaMonkey 2.0

  • All extensions will be disabled. You will still be able to select them in the Add-ons/Extensions list but only for the purpose of upgrading or uninstalling (the options button will be disabled).
  • Default toolbar settings and controls will be used.
  • The default theme will be used.

Firefox and SeaMonkey 2.1 or above

  • A window called "Firefox Safe Mode" or "SeaMonkey Safe Mode" with some troubleshooting options appears (see below).

At that point, you can either continue to Safe Mode or select some troubleshooting options and restart in normal mode to apply the changes.

If you choose to continue in Safe Mode:

  • All extensions will be disabled (but this will not reset any preferences that some extensions may modify).
  • Firefox or SeaMonkey will be using the default theme.
  • Default toolbar settings and controls will be used [6].

If you choose any of the troubleshooting options, the changes are only applied if you choose Make Changes and Restart.

Safe Mode options

Note: To run in Safe Mode without making any changes, just click the "Continue in Safe Mode" button.


When you select any of these options and click the "Make changes and restart" button, Firefox or SeaMonkey will restart in normal mode with the selected changes. Warning: These changes will remain in effect in subsequent browser sessions. Some of these changes cannot be reversed. [7]

  • Disable all add-ons - Disables all themes and extensions; starting in Firefox 3.5, this option also disables all installed plugins. [8] You can use "Tools -> Add-ons" to selectively re-enable them when you restart Firefox (details here).
  • Reset toolbars and controls (Firefox, Thunderbird) or Reset toolbars and window sizes (SeaMonkey) - Removes any toolbar customizations you may have made via the "Customize Toolbar" dialog. Also restores default window size/position and tree sort order and resolves various localstore corruption issues. Warning: Unless you made a backup copy of localstore.rdf, this change cannot be reversed without re-customizing your toolbars.
  • Delete all bookmarks except for backups (SeaMonkey or Firefox 3.6 and above [9]) or Reset bookmarks to Firefox defaults (Firefox 3.5 and below) - Replaces your bookmarks with the default set of bookmarks (your browsing history is left intact). If you select this option and want to undo the change, you will need to restore your bookmarks from backup.
  • Reset all user preferences to (Firefox or SeaMonkey) defaults - Resets any user-set preferences to the default values (except for those set in the optional user.js file) and restores the default theme. Warning: This change cannot be reversed unless you made a backup copy of the prefs.js file. Does not affect any userChrome.css or userContent.css changes.
  • Restore default search engines - Adds back all of the default search engines included with your version of Firefox or SeaMonkey, if some are missing. It does not remove any added search engines and you can later remove any unwanted search engines that were added back.


  • Make Changes and Restart - This restarts the application in normal mode and applies permanent changes in any of the options selected above.
  • Continue in Safe Mode - Starts the application in Safe Mode (this will not apply any of the options selected above).
  • Exit

See also

External links

Related bug reports