This addon is literally the only reason I use firefox.
Works perfectly. Thank you for all the support and upgrades.

Just needs some magic after upgrade to FF 57 to hide the native tabs on top of the screen (which is not the developer's fault) - see below and in other reviews as well, you can find additional information on how to do this
Also see the wiki page for this addon - there are examples for styling the tabs:
https://github.com/piroor/treestyletab/wiki/Code-snippets-for-custom-style-rules

To hide FireFox tab bar and Side Panel title:
1) Locate your firefox profile folder (you can find it in the troubleshooting section in the Settings)
2) Locate "chrome" folder there - create it if it isn't there
3) If there are no files userChrome.css and userContent.css in "chrome" folder - create them
4) At the top of userChrome.css file add:

/* add this line if it is not there */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

/* to hide the native tabs */
#TabsToolbar { visibility: collapse; }

/* to hide the sidebar header */
#sidebar-header { visibility: collapse; }

==================================================================================================

Чтобы скрыть вкладки вверху браузера, см инструкцию ниже, а также прочие отзывы. Также см вики для этого аддона - там всякие примеры, как стилизовать вкладки: https://github.com/piroor/treestyletab/wiki/Code-snippets-for-custom-style-rules
1) Находим папку профиля firefox - Настройки - Справка - Информация для решения проблем - Папка профиля - Открыть папку
2) Если в ней нет папки chrome - создаем
3) Создаем файлы userChrome.css и userContent.css в папке chrome, если их там нет
4) В начале файла userChrome.css добавляем:

/* добавить эту строку, если ее там нет */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

/* чтобы спрятать вкладки сверху браузера */
#TabsToolbar { visibility: collapse; }

/* чтобы спрятать заголовок у сайдбара */
#sidebar-header { visibility: collapse; }

This the one, the only 10-star add-on.
5 stars for the value of its mission
5 stars for execution
Firefox has some work to catch up to where it was before, but it can still handle this add-on quite well. Visual, collapsible tab tree just makes the browsing experience so much more sensible.
I'm looking forward to seeing the weird old tab bar disappear again, but that's a problem with WE not with this add-on.
I can hardly remember a time I was this happy with a browser feature since the invention of the DOM inspector.

most valuable firefox extension, and in fact the only reason to use firefox. thank you!!!

yo! I second "Can't live without it"
Thanks a LOT for this awesome extension.
Several years ago (about 6 i think), the sudden inspiration crossed my mind, that tabs should not be listed horizontally, and after some longer research at that point in time (treestyletab was lesser known), i found this and was happy EVER AFTER.
It's pretty incredible that the devs made this working with firefox Quantum out of the box, I can't believe the effort.
I just wanna say: Thank you!
And you don't even want Donations, tears in my eyes, much love :)

TST is the reason I've never even considered switching to using another browser. Works perfectly on FF57. Thank you so much for all your hard work!

Thank you for this very useful addon, cannot use browser without it.

Splendid job on converting to Firefox Quantum. With the changes to chrome.css from the wiki, it looks great!

Perfect when opening lots of tabs on a widescreen monitor. All tabs remain readable contrary to the normal tab layout.

if not this plug-in I'd give up using FF and go for Chrome!

This is must have extension. It would be even greater if it could work in tandem with ColorfulTabs.

Just to remind older comments. One can hide FireFox tab bar and Side Panel title with userChrome.css file like that:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

/* to hide the native tabs */
#TabsToolbar { visibility: collapse; }

/* to hide the sidebar header */
#sidebar-header { visibility: collapse; }

The best vertical tabs solution. I cannot use Firefox without it.

After Firefox killed TabMixPlus I thought I would have to switch to another browser. Eventually I found Tree Style Tab, which is even better. Now I just wish I had a way to turn off Firefox's own tabs, since they are so lacking in features as to be almost useless.