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Does firefox keep more than 0 record of historic sessions?

  • 3 replies
  • 1 has this problem
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  • Last reply by cor-el

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Long story short: windows update sneaked a restart under my nose caused me to lose all my previous session.

I'm attempting to recover the previous session.

I have backed up the unmodified session profile folder. But this profile folder was modified by the restart process obviously, as windows gave firefox "normal shutdown" command. How do I know that? The next time I opened it up, it's "brand new" without the "restore session" interface.

So my idea is to figure out if firefox keeps a track record of previous sessions EVEN IF THE SHUTDOWN WAS PROPER.

If it does, well I'll have to figure out a way to "trick" firefox to restore it. If it doesn't, well I'll have to manually restore it by sifting through the history.

I repeat, the key here is for me to find out whether or not firefox always keep a record of previous session somewhere.

So my question is, does it? Or does it purge all the previous session clean as long as the shutdown was deemed "correct"?

Long story short: windows update sneaked a restart under my nose caused me to lose all my previous session. I'm attempting to recover the previous session. I have backed up the unmodified session profile folder. But this profile folder was modified by the restart process obviously, as windows gave firefox "normal shutdown" command. How do I know that? The next time I opened it up, it's "brand new" without the "restore session" interface. So my idea is to figure out if firefox keeps a track record of previous sessions EVEN IF THE SHUTDOWN WAS PROPER. If it does, well I'll have to figure out a way to "trick" firefox to restore it. If it doesn't, well I'll have to manually restore it by sifting through the history. I repeat, the key here is for me to find out whether or not firefox always keep a record of previous session somewhere. So my question is, does it? Or does it purge all the previous session clean as long as the shutdown was deemed "correct"?

All Replies (3)

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In case of a shutdown due to an update then Firefox would create an upgrade file in the sessionstore-backups folder.

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 can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory).

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 try to restore a recent upgrade.jsonlz4-<build_id> when available or use a utility to browse Windows System Restore points to see if you can find a recent sessionstore.jsonlz4 file. You can look at this tool to inspect a compressed jsonlz4 sessionstore file.

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
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cor-el said

In case of a shutdown due to an update then Firefox would create an upgrade file in the sessionstore-backups folder. 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 can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory). 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 try to restore a recent upgrade.jsonlz4-<build_id> when available or use a utility to browse Windows System Restore points to see if you can find a recent sessionstore.jsonlz4 file. You can look at this tool to inspect a compressed jsonlz4 sessionstore file. 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


Thanks. Looks like by overwriting the "recover" file I did the trick. One more thing, is there a reliable session manager? I used to use this session manager addon but it is no longer available nowadays. And the most popular session extension doesn't really work reliably.

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If Firefox works properly and there are no issues like crashes of hangs when you close Firefox then extensions should work. If you regularly encounter issues with restoring the session then you can expect problems with extensions as this can't prevent the extension from updating its data whereas built-in Firefox Session Restore might still work (you may only lose the latest tab changes).