In addition, both the previous.js and upgrade.js files are not replaced as often as the two main session restore files. So what is different in comparison to the old session restore? First of all, you may notice that additional files are saved by the browser which increases the chance that one of the session restore files is not corrupt and working. And finally, upgrade.js will be tried as well.Previous.js is then used to restore the session.Recovery.js will be used if present and valid.If sessionstore.js is valid, it will be used.Here is the order in which Firefox attempts to restore the previous session on start. sessionstore-backups/upgrade.js- Session Restore data after the latest upgrade.sessionstore-backups/previous.js - Session Restore data before the second to last shut down.sessionstore-backups/recovery.bak - Contains the state of Firefox 30 seconds before shutdown or crash.sessionstore-backups/recovery.js - Contains the state of Firefox 15 seconds before shutdown or crash.sessionstore.js - The state of the browser during the last shut down.On the first start up after an upgrade, Firefox copies the sessionstore.js file to upgrade.js-.Īs mentioned before, Firefox saves several new session restore files to the user profile directory once the new feature lands in the browser (Nightly users already have it as it lands in Firefox 33 if things go as planned).During start up, if sessionstore.js is valid, it is moved to previous.js in the sessionstore-backups directory.When Firefox is shut down, a new sessionstore.js file is written to the main profile folder.Usually, recovery.js and recovery.bak contain both the state of the browser 15 seconds apart from each other.Before that happens, it will move the previous recovery.js file if tests return it as good to recovery.bak in the same folder.Firefox writes contents of Session Restore to sessionstore-backups/recovery.js whenever it is required.

They too can be used to replace the main sessionstore.js file should it be corrupt. These files contain session information from the last shutdown or upgrade.

You can still use these files and replace the sessionstore.js file in the main directory.Īdditionally, you find previous.js and upgrade.js there as well. You can use the other session backups listed there as well to restore sessions. The primary backup file is recovery.js now, the secondary backup file recovery.bak. Note that sessionstore.js is only shown when Firefox is not open. While sessionstore.js is still stored in the main Firefox profile folder, all other files are now stored in sessionstore-backups instead. Mozilla has improved the Session Restore feature in Firefox 33. May still be useful for old versions of Firefox, and Firefox-based browsers such as Pale Moon. If it does not, press the Alt-key on your keyboard and select History > Restore Previous Session. Firefox might pick up the session automatically.Paste the copied file to the root folder.Go back to the root directory of the Firefox profile.Copy the session restore backup that you want to restore, e.g.Rename recovery.backlz4 to recovery-backup.backlz4.Rename recovery.jsonlz4 to recovery-backup.jsonlz4.Open the sessionstore-backups folder of the profile.

Open the profile folder and rename the current session file sessionstore.jsonlz4 to sessionstore-backup.jsonlz4.

Make sure no instance of the browser is running. Mozilla changed the format of session backup files and that means that the previous way of restoring sessions needed updating. Use these if previous.jsonlz4 fails to do the trick.

upgrade.jsonlz4-'number' - previous session backups, usually created during upgrades of the browser.

previous.jsonlz4 - the last session backup that Firefox created.This is the file that you want to try to restore first (unless it has a very low size).

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