Maybe there is a upgrade.js-<build_id> in the sessionstore-backups folder that got created after the last update that contains these tabs.

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.

Backup the session files in the sessionstore-backups folder in the Firefox Profile Folder to make sure not to lose possible important session data. Do NOT close Firefox when Firefox is already running.

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/

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:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

cor-el, thank you so much! It worked! Only strange thing is that the newest file was not the one that was prior to the crash but a couple of days before that. It was on every day between the newest file that I just used to restore the tabs and the day that Ffox crashed. Very odd...

I think this practice of deleting sessionstore.js when restarting FF is a bad idea as is removing the history/restore session capability as soon as a new tab is created.

I closed firefox then started the never ending windows update (windows7) then on restarting firefox, I got a second tab with no attempt on my part. It was http://detectportal.firefox.com/success.txt and the restore previous session was greyed out. It would be a good day of work to go through history and try to reconstruct the tabs. This is not the first time the restore previous session has failed. As I look into current files, I see that the session restore files are not being updated properly.

The success.txt file appeared 5/13/2017 @ 23:53 so the previous session ended a short time before then but previous.js is dated 4/19/2017 which is the same as the latest upgrade-js (but it should be 5/13/2017!) by the time I looked, sessionstore.js had been overwritten (dated 5/14 12:06 AM) which is inevitable to have happened before the problem could be seen according to the description of how things should happen. There is no sessionstore.bak but there is a sessionstore.bak-20140923175406 dated 9/26/2014 so all this looks like the session data is maintained sporadically.

It seems to me that this situation should come to the attention of the fireFox programmers.

The detectportal.firefox.com domain is related to the captive Portal Service.

• network.captive-portal-service.enabled
• https://en.wikipedia.org/wiki/Captive_portal

I don't normally see anything from detectportal.firefox.com but in this case it may have defeated the restore session. Keeping sessionstore.js while firefox runs would allow restore previous session to be available at any time.

As posted above, Firefox uses previous.js to store the content of sessionstore.js from the previous session. So you should be able to restore that session at any time.

There is no longer sessionstore.bak file used, there is only sessionstore.js and that file is created when Firefox is closed properly. Otherwise there are the recovery.js and recovery.bak files that Firefox can check to see if they are valid. As a last resort there are the upgrade file created when Firefox is updated.

You can create a backup copy of sessionstore.js to have a backup of a specific session or use an extension like Session Manager.

• https://addons.mozilla.org/firefox/addon/session-manager/

Do you restore your previous session windows and tabs automatically at startup? If not, you could consider trying that setting to protect against those "some program launched a page when Firefox was closed, I closed it, oh crap there goes my session" situations that happen from time to time.

This article will get you to the setting: Startup, home page, tabs, and download settings.

If you already have that but don't see what you're looking for, try the History menu and see what closed windows you can re-open.

Unfortuantely " Firefox uses previous.js to store the content of sessionstore.js from the previous session. So you should be able to restore that session at any time." is not correct because Firefox deletes it quickly when it starts. I have confirmed this by watching the directory while starting and terminating firefox with the red X. I wish you were correct. The idea of automaticly restoreing the previous session at startup is the best autiomated idea but I wrote a bat program that saves sessionstore.js and previous.js when firefox is not running I hope it will make future recovery possible.

If you decline to restore the session then Firefox will possibly delete the previous.js file. This is usually meant to be used when you do not reopen the tabs automatically (Show my windows and tabs from last time).

I have not seen previous.js being deleted. The only reason to save it in a secure place is to keep it from being overwritten. It is sessionstore.js that gets deleted or renamed by the time forefox has produced a display. In my experimentation it seems to be renamed previous.js but in the case of the tabs loss at the beginning of this thread that did not happen. In that case sessionstore.js is gone and previous.js is old.

Please excuse my confusion. the transfer of sessionstore.js to previous.js usually happens but not always as indicated in my previous post. I have decided to save sessionstore.js in a safe place brcause of this unreliability.

robey said

Unfortuantely " Firefox uses previous.js to store the content of sessionstore.js from the previous session. So you should be able to restore that session at any time." is not correct because Firefox deletes it quickly when it starts. I have confirmed this by watching the directory while starting and terminating firefox with the red X. I wish you were correct. The idea of automaticly restoreing the previous session at startup is the best autiomated idea but I wrote a bat program that saves sessionstore.js and previous.js when firefox is not running I hope it will make future recovery possible.