As a recent Chrome uBlock Origin refugee, I was looking for something that'd replace chrome's tab groups.
This add-on does a little bit of that, but differently, and in several ways better.
First off, you WILL want to customize your browser toolbar to put the add-on icon to the top left of the app, right before the tabs. It's a much more natural place to use it.
Second, if you're using dark mode, the default icon is hard to see, and you'll have to tweak a config to fix that. It's spelled out in the "about this extension" page.
Third, if you multi-screen, this is MUCH better than chrome tab groups, since it allows you to trivially move tab groups between windows, and therefore screens.
I like that it can sync the tab groups into a bookmark folder.
The default group icons are awkward, but you can replace them with the favicon of any tab within the group, which solves that.
I just installed this a couple hours ago so I'm still wrapping my head around it, but I like it already.
I've got 12 tab groups already. Just don't expect it to be a drop-in replacement for Chrome tab groups. Take the time to wrap your head around the mental model of this add-on, it's worth it.

*Edit, now with more gripes!:
A dozen tabs or so (about 8% of my tabs) get detached from their group on every Firefox restart, which means on every Firefox update for me. I don't know why. It's not the same tabs each time. I tweaked all the settings I could, didn't help. I have to reassign the stray tabs in their proper groups after a restart, which takes entire seconds.
I'm kinda hoping this is going to stop happening on a future update. If I was a little less lazy, I'd probably try to debug it myself.

I was confused at first, didn't really understand how it worked.

The tabs are basically grouped by window, which is ok i guess but not what i was expecting.

You make a group, and if that group is active then any tab you open in firefox will be added to that group. any tab you close will be removed from the group.

If you activate a different group, your current tabs will be closed (and saved) and the new group tabs will be opened. In other words, you can't have two groups open at once.

It was unintuitive to figure out, but easy to use after figuring it out. However the functionality is not exactly what i want, the tab grouping in chrome is way better than this.

Essential plugin. Way better than Chrome tab groups. Does everything I need

Simply brilliant. Been using STG for 3 years and I'd be lost without it on any new computer. For those ONE star reviews, watch the Percy Jules YouTube video and I'm sure you will change your rating. https://www.youtube.com/watch?v=6m09F312soQ

I was looking forward to this solving my tag organization problem, but ran into two issues:

1. When creating a group, all of the open tabs were automatically added to it. I can't find an option to keep this from happening. It's certainly not the behavior I want -- I want to be able to create groups that I need, and leave all the other tabs alone, and this extension doesn't seem flexible to that extent.

2. Once all the tabs were automatically added to that group, I couldn't remove them without simultaneously deleting all of the tabs. WTF? I ended up having to walk back the entire installation, restore the session and clean up the resulting mess.

BRILLIANT! Simple, intuitive and classy. Open, create groups, drop and drag tabs between groups, then choose any one from the icon on top at any time.
I figured it out in 10 seconds, made 3 groups in 15 more, filled them in 20, and now just have to click their icon up top, and choose one of the three groups (which you can name, and which have a little color on each one).
This is a case of programming perfection: it could not have been made better!
Change colors and change icons or add your own in several common formats - download anything. Nifty!
I even grabbed a 1200x1200 pixel jpg off my PC and it worked, and shrunk it perfectly. Most websites choke on 128x128. Dude! :)

Un pur plaisir à utiliser ! Si vous aimez grouper vos activité, et économiser de la RAM en pensant de l'une à l'autre, alors cette extension est juste parfaite !

As I often work on different products and different release versions, I love to now have the possibility to create groups based on product/versions. I used to have all important Jira tasks in one window (as I do not like to have several Firefox windows opened at the same time), but thanks to this plugin I can now have them divided in different groups and switch between them easily. Pinned tasks stay visible allthough I am switching between groups which makes this plugin even better! Thank you Drive4ik!

I recently switched from Chrome and I was expecing something similar to the tab grouping feature in Chrome, since this Firefox extension is so popular and comes with the recommended tag. Instead, I got a horribly unintuitive tab grouping experience, with tabs hidden god knows where.

This one is a tab hiding extension, not a tab grouping extension.

not sure how this is even supposed to work. when i add a tab to a new group, FF will immediately hide that tab and i can't access it. Until this app is updated, ignore it

Installed and immediately added all of my open tabs to a hidden group, each of which requires several separate clicks to unhids manage or move to another group. Not visible from the extension manager, options hidden and unintuitive. Really shoudl be a basic browser functionality but not worth installing this even as an interim solution

it's perfect
me <3 containers

I'm using this addons for years and love it.
Little bugs with Tile Tabs WE addon.
Not working with Floorp browser.

I love it. Took me a few minutes to figure it out especially connected to container tabs, but I cannot do Firefox without it now. Thank you!

Buggy and unintuitive. Any time I tried to use this add-on I thought I was going to lose all my tabs just trying to get them back out of a group.

I wanted something that actually MOVED a tab into an actual group !! Not just tagged an open tab as being in a group !!!!!
With this extension, as soon as you have added the tab to a group, you think "I can close it now, it's in a group". NO IT ISN'T ! You close the tab and it's gone ! Pretty pointless extension !
Totally doesn't do what it's name implies !!!!!

The backups of this addon saved me all my tabs when the shitty Firefox 127 update decided to nuke my whole history/open tabs etc without a way to restore it. Just trusty old STG churning out backups which I could restore from. Just for that the 5 stars are justified, but on top of that it also is a very useful addon.

Great add-on. Coming from chrome it takes a bit of getting used to, as it isint as polished and intuitive. I really do only have one problem with it tho:
For some reason you cant specify where the backups folder is placed. It just defaults to where firefox's downloads folder is. And i dont want this backupfolder to be in my downloads. plz fix.