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.
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How to start Firefox in Safe Mode
At the top of the Firefox window, click the button, go over to the menuOn the menu bar, click the menuAt the top of the Firefox window, click the menu and select . Firefox will start up with the Firefox Safe Mode dialog.
firefox -safe-modeYou may need to specify the Firefox installation path (e.g. /usr/lib/firefox)
Safe Mode window
You now have three options:
- Clicking the button cancels your attempt to get into Firefox's Safe Mode.
- Clicking the 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 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
You now have two options:
- Clicking the 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 button will restore Firefox to its factory default state while saving your essential information. See Reset Firefox – easily fix most problems 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:
- Troubleshoot and diagnose Firefox problems
- Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems
- Reset Firefox preferences to troubleshoot and fix problems
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.
- See the article Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems for solutions.
Exiting Safe Mode
- At the top of the Firefox window, click on the button and then select At the top of the Firefox window, click on the menu and then select On the menu bar, click on the menu and select At the top of the Firefox window, click on the menu and select
- Start Firefox as you normally would.
- If Firefox keeps starting in Safe Mode, see Firefox is stuck in Safe Mode.
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 button.
- Disable all add-ons: If you select this box and then click 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 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 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 then all Firefox options and preferences will be set back to the default settings, and any changes you made to them will be undone. 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 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)
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