You can search the TM backup for a recent sessionstore.jsonlz4 file or if this fails search for a recovery.jsonlz4 file. The sessionstore.jsonlz4 file is only present when Firefox is closed, so in case of a crash this file is likely missing.

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

Location used for the main profile in the hidden ~/Library folder that keeps your personal data (Root Directory on about:profiles).

• ~/Library/Application Support/Firefox/Profiles/<profile>

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)

cor-el, thank you very much. Forgive me if I'm a little over-cautious here. I'm not all that 'handy.'

I looked in TM. Because I 'never' close FF unless a restart or update, there is no sessionstore.jsonlz4 file backed up - probably if I went all the way back :-) By the way, there's another folder between Profiles and the sessionstore-backups folder - ycajz1ia.default. I don't see any need for it, but there it is.

The incident took place on 11/2, so 11/1 should bring back the tabs?

Some time ago, a friend of mine who used to be an Apple developer, scolded me when I talked about going into TM, copying a file and putting it in a current folder. He said there are 'details' that the Restore function takes care of, whereas a copy-paste might not?

If your certain this isn't a problem in this case — which I'm thinking, or you wouldn't have suggested it :-), then I should copy the recovery.jsonlz4 in TM from 11/1? Then I would paste it into the current ycajz1ia.default folder and change the name to sessionstore.jsonlz4, is that correct? I have made a "sessionstore.jsonlz4 copy" of that already, so to be kind to the Finder, would I delete/remove the original before changing the name? Then start FF and WaLa!?

What do you think about clicking Restore in TM for the whole sessionstore-backups folder, then making the recovery copy for the name change from there? Or, doing Restore on just the recover file in the folder and going from there?

Much appreciated.

The ycajz1ia.default folder is likely the actual profile folder what you can confirm by checking this in the "Help -> More Troubleshooting Information" (about:support) page.

• https://support.mozilla.org/en-US/kb/use-troubleshooting-information-page-fix-firefox

I would be cautious and first copy the sessionstore file (this would be recovery.jsonlz4) from the TM backup to a location where you can inspect its content to see if it has your lost tabs.

You can look at this tool to inspect a compressed sessionstore file as present in the sessionstore-backups folder.

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

If you want Firefox to use this sessionstore file then you will have to close/Quit Firefox and copy this file to the main level of your current profile where you also see its own sessionstore-backups folder (use the button on about:support). You need to rename the file to sessionstore.jsonlz4.

Unbelievable - I wrote a reply, submitted, and the system lost it :-) So here goes again (this time, and going forward, I'm making a backup before submitting :-)

Here's a shot of my file hierarchy, FF running. ycajz1ia.default looks like just a 'container' for all the profiles. Seems redundant... Can you think of a reason for it?

It seems safe to assume that the day before the incident, when all tabs were loaded, sessionstore-backups was OK, so I think we can skip the inspection step. I will back everything up before proceeding.

sessionstore.jsonlz4 seems to be a go-between temporary FF creates when it closes, and what it looks at first when started. So it makes sense to copy recovery and rename as you say.

What I think I'll do, then, with FF closed, is let TM restore the whole sessionstore-backups folder, then copy recovery from that, rename it within the folder, trash sessionstore.jsonlz4 from ycajz1ia.default, and move the new one. Sound like a plan?

Quote: ...let TM restore the whole sessionstore-backups folder, then copy recovery from that, rename it within the folder, trash sessionstore.jsonlz4 from ycajz1ia.default, and move the new one...

Yes, that would be the way to go to restore that last session. It still wouldn't be a bad idea to check the file with the scrounger tool to know what you can expect to see. It might also be a good idea to rename the existing sessionstore-backups folder to prevent Firefox from falling back.

OK, thanks co-rel. I'll go ahead, then send result and, mercy be ours, we can mark it solved :-)

Worked perfect(ly)! :-) I'll mark the email solved. Many thanks again.