Pretty neat and simple (89KB), but not too simple! Just what I need! 'Uses the built-in sync API', that's good. Some eye candy would be nice including dark themed because add-ons always run better with eye candy😉

[later] On activation the restore 'clean' check box, it removes pined tabs, so an option to prevent that would be nice too!

This is just I am looking for, it supports normal and pinned tabbed, containered tabs too, sorting and reordering

Would be pretty special if this addon could save pages "loaded" instead of just saving the URLs and opening them back later. Otherwise what's the point of using this addon? I cant think of any reason. Since I have "Simple Tab Groups" and firefox remembers last opened tabs when I restart.. And I can use bookmarks to save private tabs or sessions. So is this extension supposed to replace the bookmarks? Makes no sense. It should at least save the pages exactly the way you see them. Let me know if you ever add this option. Until then, I cant think of any reason to use this extension.

Great Add-on
Thanks a million @emano waldeck.
However two wishes during your further dev.
1. Remove the requirement of pressing shift key to keep the saved session from being erased after restore. Forgetting to press the shift key and losing your saved sessions after closing is VERY annoying.
2. Please provide a method to save your sessions. One can restore all his saved sessions from a backup would be very convenient. Also one can share his saved sessions with someone else by sending him a small text file.
Thanks in advance.

This is such a lifesaver. Granted, I never use the password feature so I don't know how well it works. But for my purposes it's perfect!

It does the thing it says it does. Save apps. Close Firefox. Open apps later.
Nice, simple and useful. Just what I needed.

Great and works fine!