When you reset/refresh Firefox then a new profile is created and some personal data (bookmarks, history, cookies, passwords, form data) is automatically imported. The current profile folder will be moved to an "Old Firefox Data" folder on the desktop. Installed extensions and other customizations (toolbars, prefs) that you have made are lost and need to be redone.

It is possible to recover data from the old profile, but be cautious not to copy corrupted files to avoid carrying over problems.

You can copy the sessionstore.js file from the profile folder in the "Old Firefox Data" folder on the desktop to recover your tabs.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile

Thanks Cor-el,

I can find the current Firefox profile folder, but it has no file called sessionstore.js.

It does have a folder called sessionstore-backups containing an upgrade.js from a few weeks ago.

Any clues please?

sessionstore.js is only there when Firefox is closed and not while Firefox is running.

You can backup the session files in the sessionstore-backups folder in the Firefox Profile Folder to make sure not to lose possible important session data.

previous.js (cleanBackup: copy of sessionstore.js from previous session that was loaded successfully)
recovery.js (latest version of the sessionstore written during runtime)
recovery.bak (previous version of the sessionstore written during runtime)
upgrade.js-<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.js to replace the current file (make a backup copy of the current sessionstore.js).

Thanks again Cor-el.

That seems to have solved the problem.

Much appreciated.

Mike