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 sessionstore file.

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

Thanks yes I am aware of that, having done it before, but under this version of FF I can find no trace of main sessionstore.jsonlz4

Where is it found now? It used to be in the library under applications. It is not in the the profile itself. I have used search and gone though it manually and it doesn't appear. It has to be somewhere as FF still opens.

Thanks.

The sessionstore.jsonlz4 file is only present in the profile folder when Firefox is closed properly. When Firefox is running files in the sessionstore-backups folder are used.

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)

If Firefox doesn't use the sessionstore.jsonlz4 you copied then check "History -> Restore Previous Session" and possibly "History -> Recently Closed Tabs/Windows".

Did you check the sessionstore file to see whether it is not corrupted ?

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

Note that the file might not be compatible if the file is from an old Firefox version.

Thanks, Yes, and it was closed. That's why I Posted here.

These files were there:

   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)

I have solved it.

The last few times I tried this to find the sessionstore.jsonlz4 file, I rhad eached the profile by going through the Troubleshooting console and clicking the link to profile and and then closing FF.

For some reason the sessionstore.jsonlz4 did not show up. Even after refreshing the folder. However this last time when I then manually went to the library to session back ups folder it was there.

Have replaced the old sessionstore.jsonlz4 file with renamed previous session file and and all is back to normal.

Thanks.