In case you are using "Clear history when Firefox closes":

• do not clear the Browsing History

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.

Make sure that you do not run Firefox in (permanent) Private Browsing mode (Never Remember History).

• https://support.mozilla.org/kb/Private+Browsing

I have edited the title

• was firefox 24 crashes (/questions/971603)
• now saved tabs disappear, including all my Tab groups

I ALSOOOOOO have this problem. Is there a solution or workaround? Seems Firefox keeps pushing this problem aside. Anyone???

Hi trebla62, I'm not sure what is causing this issue. However, Firefox's session storage is very fragile. If Firefox is closed and the Flash updater opens it to the page telling you Flash updated and you close it without first restoring your session, boom, your previous session is gone with no way to recover.

To keep more sessions either for future reference, to protect against accidents, or as a workaround for this issue until it is solved, you could use the session manager feature of the Tab Mix Plus extension (if you use that), or the specific Session Manager extension: https://addons.mozilla.org/en-US/firefox/addon/session-manager/

This is either caused by using "Clear history when Firefox closes" to clear the history (open tabs are considered as history) or by a problem with the sessionstore.js file or other problem with session restore.

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

You can reset browser.sessionstore.* prefs that appear bold (user set) to the default value on the about:config page via the right-click context menu to make sure that Session Restore is enabled and working properly.

• http://kb.mozillazine.org/Session_Restore
• https://support.mozilla.org/kb/restore-previous-session