Almost does the job, but tab groups are destroyed, as others have mentioned.

Firefox closed all my tabs without warning and couldn't restore them from its own session backup files, even though those files contained all my tabs. This extension helped me restore them all easily, which saved me from having to restore a large number of tabs manually, one by one.
If this extension wasn't there, I would have replaced Firefox with another browser.

Once every few months, it randomly dedices to delete all my sessions and reset my settings. Absolute trash.

This extension used to be great! I donated a few times. Today I had to force restart my computer and Firefox came up with no tabs! I checked the Tab Session Manager and the last save it had was from over a year ago! I guess the auto save doesn't work any more and all the sessions I did have saved are gone. This extension is totally broken now.

STILL DEAD!

Did not save the "tree" from "tree stile tabs", and I did make sure to have "Restore tree state of Tree Style Tab." checked.

Unlike the session restore built into Firefox, this add-on does not retain or associate an individual tab's browsing history when a new browser session is launched. I use this quite a lot, so I may look for a different add-on which does support this.

Would've rated it higher had the manual export setting functionality included the sessions I had saved.

Doesn't save tab groups. Also says it supports importing JSON files from Session Buddy, but it does no such thing. It gives me a read failed error.

Used to be one of my absolute favourite extensions, but since stopped working as intended. It does save my browser windows, but I can't restore them except for clicking and restoring every tab single-handedly.

It has saved me several times when I've closed windows with at least 500 tabs that I don't want to lose this makes sure i can take my time to go through them.

Also why is this not standard with firefox?

Es öffnet die Tabs doppelt. Duplicates the saved windows and doubles up on my memory usage. Ich habe gewartet ob es ein Update gibt, aber als letztes Update steht 28.03.2025

The delete button is very close to open button and because of that, some time I clicked on wrong button to delete instead of open. It would be better if you add confirm dialog before do delete the session (even you already had undo but it will be better to ask for confirmation on delete).

I had around 500 tabs open that failed to get restored beyond the first 10 when I shut Firefox down, which hadn't happened before. This extension brought them all back which saved me quite the headache. Of course, it couldn't bring back the groups from Tree Style Tab, but it was unrealistic to expect it to save another extension's data.

"Support tab groups" is false advertising -- or it's only true insofar as it will save the tabs /within/ tab groups just fine, as long as you didn't actually want to /keep/ those tab groups

over 5k tabs recovered from a saved file. could be improved but saved me big time

For years now Firefox session restore only puts the first window at the same position, the feature to let Tab Session Manager do this is golden as windows are now always restored in the same order. The easy access to auto session backups also golden. Together with Winger extension to stash windows, finally an upgraded browse experience which works nice and safe for 1000's of tabs over a 100 windows ; ))

While it's come a long way since its inception (I switched to this after a feature-rich and reliable session manager that I used was discontinued after Firefox's engine overhaul), it still seems to act up sometimes with too many tabs open.