Absolutely hideous since Firefox 57.0 launched.
It's probably something rather fundamental that has changed in Firefox that means I'm not stuck with the default tab style AS WELL as the tree style tab.

I think Piro has either reached obsolescence or lost sight of the original idea.
I wanted less screen wastage, now I've got a button, and the tree tabs have a header, *and* I've got the tabs at the top.

If I can't get rid of the regular tab style, I will just have to get used to it.

Real shame - I've been using Tree Style tabs for years, and you've been perfect - but now it's much too ugly to use.

I'm sorry. :(

E' così comodo in verticale tutti i tab

Thank goodness you have updated for Ff 57. It was showing as "legacy" and I was dreading the loss of TST. But it isn't as good (yet): The cross for closing a tab is on the left, even when the tree is on the right of the browser - I always have it on the right. And the Ff tabs show along the top as well as TST's tree at the side! I know it's early days but I hope you'll fix these two things very soon.

Also, thank you for the instructions for converting session information manually - but I'm fairly tech savvy and didn't find it straightforward. Many users won't know how to start "command prompt", how to find the profile directory, where to look for about:support. I corrected/removed a typo in the code you gave (intelligent guessing based on distant memories of DOS - I decided to risk it! I'm not a programmer) - but not everyone will know to copy and paste that, nor to paste each line one at a time, nor to remove the C:...> from each line. These things aren't obvious if you don't already know. Then I looked at the addon options, after converting the session info because that came up first of all, and saw another way of converting (not manually) but no advice how to do it; maybe that would have been more sensible, I can't tell.

Some user feedback for you, the "non-techy" point of view. :) Overall though, very very glad to have Tree Style Tabs as I'd never want to live without it. :)

UPDATE 18th Nov '17: Just been surprised by a tab opening that told me why the top tab bar can't be hidden. I'm not techy enough to risk the workaround, I have no experience customising CSS. I understand it's the fault of Firefox and can wait... hoping it isn't too long a wait! But in the meantime: (1) Can we have a context menu link to settings, instead of having to open extensions manager, please? and (2) the "Allow to create bookmarks" checkbox (under "Bookmark this tree" in the context menu options) won't allow me to select it, it just blinks and stays unchecked. Oh, and (3) the option for fixing the width back in the context menu - if that's even possible, now we're forced into using the sidebar instead of "real" tabs-at-the-side?

I really don't like any other browsers, I periodically try them all again (whenever I get fed up with Firefox!) - especially since Ff stopped supporting Java - but I don't know if I can cope without Tree Style Tab. Let's hope the voice of the masses is heard, so many people feel trapped and cheated by this unwanted update to 57. Looking foward to whatever you can do to make TST great again. :)

Its my favourite add-on. One star less because the 57 version does not hide the standard tabs.

Great thanks!!!

If you're like me and primarily used this add-on to remove the tabs from the top, follow these instructions provided by user Soulyaris:

"Inside your profile folder(it usual c:\Users\*user*\AppData\Roaming\Mozilla\Firefox\Profiles\*something*-default (check date of modified), create a new folder named chrome. Inside the chrome folder, create two new files, userChrome.css and userContent.css. At the top of userChrome.css, add the following code:
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/* Hides tab bar*/
#TabsToolbar { visibility: collapse; }
Save it and restart firefox. Enjoy."

Really great add-on. I'm sad to see one of its core features get changed. I hope it gets fixed.

Firefoxが57になりこのアドオンが最新版に更新された結果、ブックマークサイドバーにタブツリーが統合されてしまい、大変不便になりました。自分の使い方として左サイドバーにブックマークを表示し、右側にツリー型タブというスタイルでしたので、現状の仕様に困っています。もし、作者様にもどうにもならない仕様の更新でしたら申し訳ありません。

This extension is the only reason I still use Firefox. Something like this should be built into the browser really. Big thanks to the developer and for the effort made for it to work with the new Quantum (57) version. Required some tweaking to make it look the way I like but now works perfectly.

Make sure to visit the addon wiki for tips how to make the most of it (https://github.com/piroor/treestyletab/wiki).

I installed it because I read it could place my Tabs back to the Bottom, but it can't .
Don't know if it has any other useful features ( seems to be too Complex for a "Normal" User )

Have just started using this with FF57, as the "list tabs" drop down that I'm familiar with from v. 56 and earlier seems to have gone AWOL. Tree Style Tab addon meets this need nicely, even if a bit more cumbersome than the old button used to be.

On the plus side, it has more features that I'm guessing I will grow into: it took me a moment to find the "expand/collapse all" toggle, for example, but it's there! The themes are decent, but I would prefer one that didn't differentiate the "sidebar background" from the "tab background" -- perhaps there is one already, though. Also, it would be nice to have an option with more compressed presentation.

On the whole, though, quite a valuable addon, and kudos to the developer for having this ready to run in the new world of Firefox Quantum.

Скрываем вкладки сверху/How you can hide tabs on top
Russian:
Идем в папку профиля фаерфокса. Обычно это лежит в c:\Users\*user*\AppData\Roaming\Mozilla\Firefox\Profiles\*что-нибудь*-default (смотрите по дате измения). Заходим, создаем папку chrome, в ней сосздаем 2 файла userChrome.css и userContent.css(достаточно первого). В файле userChrome.css пишем:
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/* Следующая строка будет прятать вкладки*/
#TabsToolbar { visibility: collapse; }
Сохраняем, идем в about:config, ставим toolkit.legacyUserProfileCustomizations.stylesheets в true, перезапускаем огнелис. Радуемся.
English
Inside your profile folder(it usual c:\Users\*user*\AppData\Roaming\Mozilla\Firefox\Profiles\*something*-default (check date of modified), create a new folder named chrome. Inside the chrome folder, create two new files, userChrome.css and userContent.css. At the top of userChrome.css, add the following code:
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/* Hides tab bar*/
#TabsToolbar { visibility: collapse; }
Save it, check toolkit.legacyUserProfileCustomizations.stylesheets in about:config(in FF) is true, and restart firefox. Enjoy.

I'd like to try this, but can't... attempting install tells me that my FF 57 is really 48, and refuses. This is on 64-bit Debian, in case that matters.

What's with the permissions requirement?

This add-on is amazing. Instant fan.

Fantastic extension that helps me manage all the tabs I need to have open everyday. However, FireFox 57.0 update was the worst thing that could ever happen. The extension is not working as it used to and the worst, I have to deal with the traditional horizontal tabs that FireFox offers.

Come on guys, new Firefox 57 has been just released, of course the Tree-style can have some bugs, wait a little.
I'm very grateful to the author for the fast adaptation of the addon to the new FF.
Tree-style was, is and will be must-have even with some bugs.
I'm going to donate.

For those concerned about one of the most recent TST updates (I believe it's 2.2.8) that requires your permission to "Access your data for all websites", note that Piro addresses this concern in issue #1536 on TST's github project, specifically in the following comment: https://github.com/piroor/treestyletab/issues/1536#issuecomment-344792173.

I was concerned about this permission request at first, especially since I have enjoyed TST for so long and didn't want to stop using due to permission overreach. However I think I can accept the risk based on Piro's explanation of why Firefox issues the warning.

Thanks for the great add-on, Piro! I really appreciate your hard work :)

После внезапного краха всё дерево было утрачено. Теперь нужно создавать с нуля. С Tab Groups такого никогда небыло.