Best extension hands down.

works well, and, is simiarly to the screenshots. If you like side tabs, this is a great add on.

This is an excellent, free tool. It's super handy for keeping my tabs organized. It has the occasional glitch, but I seem to be able to clear them by pressing F1 twice (to close the Tree Style Tab pane and reopen it).

This plugin was one of the reasons why I moved back to use Firefox. This feature should be default in all the browsers.

The horizontal tab bar can be hidden via userChrome.css, see: https://gist.github.com/alexandru/0f8b9a845342dd919d48dccc844a7135

This is the addon that keeps me locked to Firefox - I simply can't move to a browser without vertical tabs. Thank you, Piro.

best extension

This great addon is the main reason why I'm using Firefox.

導入してからタブを探し回る事が減りました。

サイドバーにタブを表示するアドオンは他にもいくつかありますが、複数の階層に分けて分かりやすく整理できるものはこれだけだと思います（派生型を除く）。

Vivaldiのようにサムネイルも表示できればなお良し。