Reset Firefox

                     Over time Firefox can develop problems like slowness, crashing, unwanted toolbars and more. Troubleshooting and fixing these issues can be difficult and time consuming. The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
  

What does the reset feature do?

                    All of your Firefox settings and personal information are stored in your profile folder. The reset feature works by creating a new profile folder for you while saving your most important data.
Firefox will try to keep the following data:

• Bookmarks
• Browsing history
• Passwords
• Cookies
• Web form auto-fill information

The following items and settings will be restored or removed:

• Extensions and themes: Although they can be incredibly helpful, some extensions and themes can cause problems. If you need to reinstall important extensions, see Find and install add-ons to add features to Firefox for help.
• Open tabs, windows and tab groups: The reset process will close all open websites. Since your bookmarks and browsing history are saved you should still be able to easily return to your favorite sites. See Where can I find my bookmarks? and Awesome Bar - Find your bookmarks, history and tabs when you type in the address bar for more info. Also, since your cookies are saved, you shouldn't be logged out of any websites you were logged in to before the reset.
• Site-specific preferences, search engines, personal dictionary, download history, DOM storage, security certificate settings, security device settings, download actions, plugin MIME types, toolbar customizations and user styles are also not saved. See the Profiles - Where Firefox stores your bookmarks, passwords and other user data article for more information about these.
• All Firefox Services, including Facebook Messenger for Firefox will be removed. 

 How do I reset Firefox to its default state?

1. At the top of the Firefox window, click the Firefox button, go over to the Help sub-menu
   and select Troubleshooting Information.

   

2. Click the Reset Firefox… button in the upper-right corner of the Troubleshooting Information page.

   

3. To continue, click Reset Firefox in the confirmation window that opens.
4. Firefox will close and be reset. When it's done, a window will list the information that was imported. Click Finish and Firefox will open.