App (pinned) tabs and Tab Groups (Panorama) are stored as part of the session data [1] in the file sessionstore.js [2] in the Firefox profile folder [3].

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

• [1] http://kb.mozillazine.org/Session_Restore
• [2] http://kb.mozillazine.org/sessionstore.js
• [3] http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox

It is also possible to use the "Show my windows and tabs from last time" setting, that is usually a more reliable way to restore session data.

• Firefox/Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

Thank you for your reply. I would still like to use the "tab groups" feature which is similar to the Google Chrome "most visited".

I've tried several add-ons but none is a real alternative to Chrome.

I don't see the point of tab groups if the tabs that I group are not visible after a restart