Need to learn how to start Firefox in Safe Mode? If Firefox won’t start due to an add-on or modification, you can correct the problem in Safe Mode.
By default an icon is installed called Mozilla Firefox (Safe Mode) that you can use. If this icon is not available, you can do the following:
You can hold the Windows Key while pressing R to bring up the Run dialog box. From there, you can type firefox -safe-mode, then press “Enter“. Firefox will then start in Safe Mode.
If you’re already using Firefox, and wish to restart the browser in Safe Mode, you can select the “Restart with Add-ons Disabled…” option under the “Help” menu. Restarting with Add-ons disabled is the same as starting in Safe Mode.
Mac OS X
In Mac OS X open Applications > Utilities > Terminal > Run (for Firefox):, type /Applications/Firefox.app/Contents/MacOS/firefox -safe-mode, then press “Enter“.
Now you have a chance to uninstall a plug-in or change the setting that caused Firefox to malfunction.