Safe Mode

Safe Mode applies to both Firefox and Thunderbird. To access it in Thunderbird in the following article, replace all instances of "firefox" or "Firefox" in the command line commands with "thunderbird" or "Thunderbird", respectively.

Safe Mode is a Firefox startup mode where all the extensions you have installed are disabled and the default theme is used. This is useful for debugging and seeing which extension might be causing a problem, especially since extensions are known to act up. Safe Mode is always a handy option to revert to if things begin to go wrong (for example, Firefox opens with no theme and everything is white).

If you have accidentally deleted the shortcut to Firefox's Safe Mode from the Start Menu on Windows, you can re-access it by going to "Start -> Run" (on Windows) and running:

"C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode

On Linux, you can go to your Terminal and run:

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

On Mac OS X, it will look like:

/Applications/Firefox.app/Contents/MacOS/firefox -safe-mode

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