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How to restore previous session that was removed because of update?

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  • Last reply by cor-el

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I HEAVILY rely on "Restore Previous Session" so much that I had it for over a year. Ever since this most recent firefox update, my restore previous session is gone. I have a recovery.js file from 2 months ago, and I am trying to restore it on the new firefox. I am trying to find guides on restoring it, but I can only find guides for the previous version of firefox.

I HEAVILY rely on "Restore Previous Session" so much that I had it for over a year. Ever since this most recent firefox update, my restore previous session is gone. I have a recovery.js file from 2 months ago, and I am trying to restore it on the new firefox. I am trying to find guides on restoring it, but I can only find guides for the previous version of firefox.

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You need to copy the recovery.js to sessionstore.js in the main level of the profile folder. You need to remove an existing sessionstore.jsonlz4 file and rename the sessionstore-backups folder to prevent Firefox from falling back to compressed .jsonlz4 files.

Do you see files in the sessionstore-backups folder in the profile folder?

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.

Does it work better with this startup setting?

  • "Show my windows and tabs from last time"

You can check if you have an "Old Firefox Data" folder on the desktop in case the Refresh feature in Firefox has been used and a new profile has been created.


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 56+ releases compress the files in the sessionstore-backups folder and sessionstore.jsonlz4 with LZ4 (.jsonlz4 instead of .js), so it is no longer easy to inspect them.