You can try to restore the upgrade.jsonlz4 file from the last update or use a utility to browse Windows System Restore points to see if you can find a recent sessionstore.jsonlz4 file.

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.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

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 with Firefox closed.

• make sure to backup the current sessionstore.jsonlz4

You can look at this tool to inspect a compressed jsonlz4 sessionstore file. This tool works locally, no uploading done.

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

I appreciate the reply, but still not sure the specific actions to take in order to restore these tabs?

Hi all - the restore session problem happened again. i lost all my tabs w firefox not providing option to "restore all tabs"

Any suggestions?

Thanks!

For future prevention:

On Mac closing Firefox can be more complicated because you can close all open windows, but keep Firefox running with the menu bar visible or minimized in the Doc.

Make sure to use "Quit Firefox" with all windows still open, especially if you want to use "Restore Previous Session". Otherwise check "History -> Restore Previous Session" and "History -> Recently Closed Tabs/Windows".

Did you try "History -> Restore Previous Session" if applicable ?

You can only restore a lost session if you have a sessionstore file like I posted above Do you have a possible candidate to check with the scrounger tool ?

If you use the Time Machine or other backup then try to restore file(s) from this backup.

• https://support.apple.com/guide/mac-help/restore-files-mh11422/mac