Must have plugin! By far the best one among Tab Managers! It uses FF builtin session manager making it much more reliable. I've tried all of them, this one deserves the highest rating, no competition. It auto-saves with a timed interval. It can almost replace OneTab since it shows you all opened Tabs and Windows as well, per saved session, plus you can name your saved sessions. Never run out of your long-winded research Windows by accident etc. Last but not least; The GUI is better designed than the others out there, making it perfect for even the beginner to get what it does.