In case you use "Clear history when Firefox closes". *do not clear the Browsing History This is because that setting overrides your Session Restore setting. *Options/Preferences -> Privacy -> Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" -> Settings *https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox *clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data *clearing "Cookies" will remove all selected cookies including cookies with an "Allow" exception you may want to keep ---- If this isn't working then use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox title bar. *"3-bar" menu button -> Exit (Power button) *Windows: File -> Exit *Mac: Firefox -> Quit Firefox *Linux: File -> Quit You can also check if Firefox creates backups in the sessionstore-backups folder in the profile folder. You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox 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/