Review for Session Manager by TheQwerty0
Rated 5 out of 5 stars
This extension is fantastic, and I've used it for years. Really a shame it's going away.
For everyone who wants to recover their sessions, they're actually just text files in your Firefox profile folder. I wrote a small app to read the files and show you your windows and tabs: https://nstoler.com/misc/sessionrecover
All the processing will be done on your computer, without sending any data to my server. But if you'd rather do it yourself, I wrote a Python script you can run on your own computer:
https://gist.github.com/NickSto/74dc6e6887bf4785bedc09d2bea2bf9b
Just run it like so:
$ ./session-manager.py -tu ~/.mozilla/firefox/8h177b3u.default/sessions/backup-2.session
If you're not able to run Python on the command line, you could still try to read the session file manually.
See here for instructions on finding your Firefox profile folder:
https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
The sessions are stored in there, in a folder named "sessions". Each session is a text file ending in ".session" that you can open in TextEdit, Notepad, or gedit.
Each file is 5 lines, with the 5th being a big JSON jumble that contains the urls of all your open tabs for that session. It gets a bit tricky from here, but if you want you can just Ctrl+F for '"url":' and find all possible tabs. The complication is that most of those urls aren't the currently open page in the tab, but a page from its history. The last item in the "entries" list will be the currently open page in the tab.
To create your own collections, you must have a Mozilla Add-ons account.