If there is no incremental backup of the session as you mentioned then you can't restore or find it. If you closed the Browser before reloading the previous session it most likely is gone.

Did you try to restore the previous session and in that session check "History -> Recently Closed Tabs/Windows"?

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.jsonlz4 (cleanBackup: copy of sessionstore.jsonlz4 from previous session that was loaded successfully)
• recovery.jsonlz4 (latest version of sessionstore.jsonlz4 written during runtime)
• recovery.baklz4 (previous version of sessionstore.jsonlz4 written during runtime)
• upgrade.jsonlz4-<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.jsonlz4 to replace the current file (make sure to backup the current sessionstore.jsonlz4).

Firefox uses the sessionstore.jsonlz4 file in the profile folder to store session data. The sessionstore.jsonlz4 file is only present when Firefox is closed. The sessionstore.jsonlz4 file is created from recovery.jsonlz4 when you close Firefox and is removed and copied to previous.jsonlz4 when you start Firefox to make is possible to restore the session at any time.

Hi cor-el, yes that is where I am up to but Martin's (GHack) advice only has pre-FF57 file names. I have backed up Sessionstore-backup files but stupidly went back into FF57 and of course it only restored the last single opened tab :( FF57 still open and have copied all above files into new sub-folder called "Recovery". So the piece of information I was missing is that there is no current Sessionstore.jsonlz4 (because FF57 still open?). I have Recovery.jsonlz4 and Previous.jsonlz4 and also Recovery.baklz4 as in the attached file.

Which goes where? :)

Thanks AJ

You can use this tool to inspect a compressed sessionstore file.

• https://www.jeffersonscher.com/res/scrounger.html

To use such a sessionstore file you need to copy the file as sessionstore.jsonlz4 to the main profile folder while Firefox is closed to replace an existing sessionstore.jsonlz4.

Cor-el - I have used scrounger and looked into File name: previous.jsonlz4; Size: 7110381; last modified 11/24/2018, 3:58:44 PM. It seems to have the Trello session (1 tab) and the "normal" FF57 session (60+ tabs) which is the actual session I want restored (The Trello one is currently the only one in FF57) and of course does not have any history of the other session.

Procedure from here? 1. shut down FF57 forcing it write sessionstore.jsonlz4 2. copy sessionstore.jsonlz4 to "recovery" folder (as back up). 3. copy previous.jsonlz4 to sessionstore.jsonlz4 in sessionstore-backups folder (overwrite). 4. Re-start FF57.

Thanks AJ

Save the backup copy of the present sessionstore.jsonlz4 elsewhere or rename the file to sessionstoreOLD.jsonlz4. With Firefox closed you need to copy previous.jsonlz4 to the main profile folder where you found sessionstore.jsonlz4 and rename previous.jsonlz4 to sessionstore.jsonlz4, so that Firefox can use this file. You already had renamed/removed the sessionstore.jsonlz4 that Firefox created, so that shouldn't cause a problem. After restarting Firefox you can check if this has worked and the session is restored. If necessary use "History -> Restore Previous Session" and History -> Recently Closed Tabs/Windows.

Started this process and went to ...\Profiles\zj0bjxvo.default, and noted sessionstore.jsonlz4 was showing in the folder then ended FF57, and went back to File Explorer only to see sessionstore.jsonlz4 disappear from the folder (presumably as FF57 rolled out of memory). Was just about to rename sessionstore.jsonlz4 and copy previous.jsonlz4 to sessionstore.jsonlz4 but now I am not sure I am in the right folder?

There doesn't seem to be a saved copy of sessionstore.jsonlz4?

Any thoughts? AJ

In what folder did you find this file?

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

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

Hi cor-el - yes that is the correct profile folder name - i.e. C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\ with the last bit being ...Profiles\zj0bjxvo.default\ with (for example) the old sessionstore.js (for pre FF57 version) in that folder. So I'm in the right place but there is no sessionstore.jsonlz4 file there any more as explained above :)

sessionstore.jsonlz4 is only present when Firefox is closed, so you won't find it while Firefox is running.

Interesting - I am finding the reverse is true, sessionstore.jsonlz4 is not available if FF57 is not running (FF57 not currently running and sessionstore.jsonlz4 not on disk anywhere (I have checked Task Manager and FF57 definitely not running :))

So should I 1. rename the current "previous.jsonlz4" to *.old then 2. find my old, saved "previous.jsonlz4" and copy into current Profile folder, then 3. restart FF57?

AJ