Sorry to hear about this problem. Considering that you have restored something, are there any useful windows listed on either of these menus: * "3-bar" menu button > History > Recently Closed Windows * "Library" toolbar button > History > Recently Closed Windows * (menu bar) History > Recently Closed Windows ''Note:'' Each window also has its own Recently Closed Tabs list. ---- If they aren't visible there, it's possible that you have an embedded session. You're already familiar with the session history files, so I'd like to introduce you to a tool I have on my site here: https://www.jeffersonscher.com/ffu/scrounger.html You can drop either your current recovery.jsonlz4 file or a backup file onto the large box to decompress the file. Then you should be able to list out its contents using the "Scrounge URLs" button. If the list looks useful, go ahead and archive it using the "Save List" button. Does the list indicate an embedded session? If so, there's a separate button to try to extract a JSON-format file of the embedded session. Firefox will preferentially restore sessionstore.jsonlz4 (the newer format), but if it doesn't find any relevant files, it may be able to restore a sessionstore.js file (the older format) at startup. Lately users report it's harder to convince Firefox to use it, but I wouldn't give up hope.