Well that was odd, decided to check addons and started firefox in safe mode and my pinned tabs were there so restarted it to disable addons one by one but before I could do anything my pinned tabs were back in place. Lets hope it lasts.

App (pinned) tabs and Tab Groups (Panorama) are stored as part of the session data in the file sessionstore.js in the Firefox profile folder.

Make sure that you do not use "Clear Recent History" to clear the "Browsing History" when Firefox is closed because that prevails and prevents Firefox from opening tabs from the previous session.

• https://support.mozilla.com/kb/Clear+Recent+History

Thanks for that suggestion, Corel but I hadn't got "Clear recent history" ticked so that wasn't it.

So far it's still fine so maybe it was just a blip.

I had the exact same problem and repaired it using this method. I too hope that it will stick now. :) Thanks for posting your findings on this Dozydora! :)

Session variables is not a viable way to pin tabs. The potential for all sorts of complications is obvious. A pinned tab should use a special category of bookmark so that even if the tab is lost during shutdown, the program has a way to reintialize it. Maintaining maximum privacy and security should not be at the sacrifice of a simple feature that should have been implemented in a better way.