Updated Review: The recent update a day ago resulted in the add-in being unable to load. Agreed, I have a lot of tabs open (approaching 90), but I have plenty of memory and that's why I use this Add-in.
In fact, its why I use FireFox.

Reinstalled v 3.9.22
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Been using this for 10 years. My 5 * review from 7 years ago is below.

Please continue supporting this for FF57. It shows up in my FF56 still as being a legacy extension. Like lot of others, it's the reason I use FF. I like being able to drag a group off-pane and creating a new FF window with these tabs present.

My main suggestion for improvement though would be for the new Tabs to appear at the bottom of the list, not as children of a current tab. Swap the current Cntl Click function to creating tabs as child tabs.

It would also be nice if the currently active Tab changed colour to something bright and in yer face. I'm often on screens and lose track of which tab it is from when I wish to close the screen.

Does what it says on the tin, no useless or overcushioned functions. Supports WE, and makes heavy-tab browsing much easier.

What's best is that NO other browser or extension can do this. Only TST can.

Like many other commenters, the possibility of having tabs
1) on the side
2) ordered as a tree
is one of the main draws of Firefox (privacy enhancements and extensions being another).

However, in Firefox 57 on MacOS, the performance with the add-on seems worse than with the native tabs UI, both at startup (when displaying my 100+ tabs) or when I opend many tabs in a short span of time.

The problem could well be due to the WebExtensions API that it uses and not the add-on itself, but it'd be great if you could confirm that you have thought about optimizations, piroor.

But most importantly: thanks for your work! :)

PS: I also had an issue a month ago, not long after upgrading to v57, where the extension would permanently use up a lot of CPU (the load went down as soon as I disabled it, so the causation link was pretty clear). I ended up solving it by saving all my tabs as bookmarks, clearing the tabs, then restoring them: the previous tree must have been "corrupted" in some way.

Tried every setting I could to prevent child tabs from every being closed, but I was still losing tabs when closing *some* parents. Tried promotion, dummy, only when tst is open, etc.

Very nice addon quite useful to manage tabs.

F1 is a nice shortcut ... but I prefer personaly F4 ... is there a way for me to change this somewhere ?

I had a look and found "F1" in the manifest.json ... (opened it with 7zip) ... but changing this just breaks the addon ...
So ... Please, tell me how to do this ...

Great addon but sometimes stops working. A restart will make it work again, but tabs and windows that I'd closed appear again. Real weird. Was fine until latest update, and I'm sure it will be fine again.

When working it's a useful addon and when devs have the ability to hide the top tab strip, we'll get a little vertical space back. Trees are great, too.

This is a great add-on. Gotta love those trees.

Because of that it's also much better than Tab Center Redux.

There is just a little thing missing. Make it so "unloaded" (not unread) tabs are visually distinguishable e.g. gray and italic font.
Maybe it's possible with some css in the advanced section but I couldn't figure out the tag for unloaded/pending tabs.
".tab.pending .label ..." doesn't work apparently

PS: Got it. It's "discarded". So if you want to give unloaded/pending/discarded tabs grey labels use this:
.tab.discarded .label {
color: grey !important;
}

5*

Great tree style tab addon. Maybe the best. One thing that i would changed: ability to close tab tree by middle mouse or by right click in first level of menu(would be much faster than now clicking from sub-menu). Thx for great addon! :-)

Now, in Fx 56.0.1 (at least 64 bit, Win10) the version Tree style tab 0.19.2017090601 is works (show in https://addons.mozilla.org/en/firefox/addon/tree-style-tab/versions/ ). But 2.x.x is "not compatible" yet.

But in Fx Developer Edition (57.0b11) Tree Style Tabs 2.0.8 is works (with new style of tabs by default).

Simply essential

Когда уже выйдет версия под последнюю лису? Я годами использовал аддон и без него сейчас как без рук. Поставлю 5, когда обновите.

"Tree style tab" is the reason why i'm on firefox. Unfortunately, this new version is the reason why i switched to Firefox-ESR until this becomes usable.

Closing some tabs causes others to be closed as well, most likely only tabs on right side of the closed one.

I would love to try this add-on, but Firefox 56.0 refuses to install it.
Why does this add-on require version 57?

this plugin should be default in all browsers. Unfortunately it doesn't work well with last versions of Firefox :/ it's slow and doesn't look as good as before. But because it's been awesome until now it still deserves 5 stars. I just wish Firefox would put more effort to support this first class plugin.

If I can't use it in FF57, I will switch to Vivaldi. Have used FF since Phoenix 0.6 so this would be traumatic.

If chrome had this, I would be using that browser. I can't find any way to donate to you, do you have a donation page somewhere?

Very nice add-on. Once you're used to it, you do not want to go back.

Ну наконец-то, свершилось! Не глючное и быстрое дополнение древовидных вкладок, качественное визуальное оформление. Автор божественнен!

Tree style tabs is an absolutely essential browser add on for me. I can't thank the author Piro enough for all the YEARS of keeping this up to date and now that he's even supporting Firefox 57 I'm just amazed. This feature should be a part of Firefox's core experience. It's the biggest differentiator between FF and Chrome and it's why I will open often upwards of 200 tabs (I'm not exaggerating) without issue and keep those trees of tabs open for weeks as I work through certain issues and only close them when I'm ready to move on. In fact, Tree Style Tab removes the need for Bookmarks as it saves not only the page but the trail of history that led you there. I will often Google a topic and then control click the first 6 links then go through the tabs closing the links that aren't helpful. It's a huge time saver and just works in a way that really clicks with me.

Perfect add-on! Using it for years...
Also new webextension version is working fine (in FF57 beta)
Would be nice if one could disable showing standard tabs..but as on could read e.g. on https://news.ycombinator.com/item?id=15342379
new API doesn't allow it yet (workarrounds for this could be also found in link above).
Another point which would ad the "icing on the cake" would be a possibility to show number of open tabs in the addnewtab field below last tab. This would help to be reminded when it's time to close some...