Its very nice if you dont want or can't use the Zen Browser(Firefoxbased) But I use and recoment the Zen Browser! :D

searched among other extensions the copy of Opera features, this one is the best!

Main reason to use Firefox

Amazing! Exactly what I'm looking for. Just had to set it to auto-hide tabs when I get out of the group, and now it works perfectly. I love this so much!

I created this profile just to give 5 stars to this add-on. That's how good it is.

Would be worth it only for the scrolling through tabs part, but it has so so much more to it. Great for keeping tabs organized.

I'm under the impression that this is the way Firefox's vertical tabs should work.
Certainly, not for novice users, but maybe simply an optional "Advanced Mode" or something similar, that we could just enable from Settings and then have this kind of extremely versatile and powerful tabs, groups, etc., tools at hand. (Tabs unloading!)
Still learning it and day-by-day liking it more and more.
ShyFox theme and Zen Browser seem to use Sidebery natively.
Sidebery is just glorious. <3

One of the main reasons why I just recently switched (at least for now) from Edge to Firefox / Floorp. I like it better than the vertical tabs feature in Edge. More compact and more features. Thanks

As close as I can get to mimicking Arc on Firefox

This extension is really useful