Firefox comes in two or more folders on all computers. They are;

Maintenance: (Programs Folder) <Windows Only> Firefox itself: (Programs Folder) And at least one folder in the profile of each user on the computer.

If you remove the Firefox folder, the user folders would not be affected.

Just to be sure, you can make a backup copy of sessionstore.js.

Having a backup of important personal data is always a good idea.

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/Recovering+important+data+from+an+old+profile

Firefox uses sessionstore.js in the profile folder to store session data. Sessionstore.js is only present when Firefox is closed. The sessionstore.js file is created from recovery.js when you close Firefox and is removed and copied to previous.js when you start Firefox to make is possible to restore the session at any time.

You will normally find these files in the sessionstore-backups folder:

• previous.js (cleanBackup: copy of sessionstore.js from previous session that was loaded successfully)
• recovery.js (latest version of the sessionstore written during runtime)
• recovery.bak (previous version of the sessionstore written during runtime)
• upgrade.js-<build_id> (backup created during an upgrade of Firefox)

You can copy a file from the sessionstore-backups folder to the main profile and rename the file to sessionstore.js to replace the current file (make a backup copy of the current sessionstore.js).

See also:

• http://www.ghacks.net/2014/06/27/mozilla-launches-improved-session-restore-firefox-33/