An excerpt from the repository, fetched Nov 13, 2026.
Read the project’s introduction
Tree Style Tab (aka TST)
This extension to Firefox provides the ability to work with tabs as "trees".
New tabs opened from the current tab are automatically organized as "children" of the current tab.
Such "branches" are easily folded (collapsed) by clicking on the arrow shown in the "parent" tab, so you no longer need to suffer from too many visible tabs.
If you want, you can restructure the tree via drag and drop.
Such a tree of tabs will behave like a visual browsing history for you.
For example, if you see a list of search results for a topic, each search result link will open in new child tab.
New tabs opened from these "child" tabs will appear as descendants of their originating tabs.
You'll easily dig and dig deeply, without losing your browsing trail - if you want to go back to the original search result, you just have to switch to the "root" tab.
Moreover, each tree will reflect a group of tabs on a similar topic.
Please enjoy as you like!
Release builds
The signed package of the latest version is available at Mozilla Add-ons (AMO). See also the strict_min_version information in the install manifest to know the minimum supported Firefox version.
Old packages are also downloadable on the AMO website. TST sometimes drops outdated versions of Firefox, but you may find old packages that support the dropped versions of Firefox.
For even older versions of Firefox, Waterfox, or Palemoon, Classic Add-ons Archive possibly contains legacy packages of TST.
Development builds
Builds for each commit are available at "Artifacts" of the CI/CD action.
Please note that you need to log in to the GitHub to see artifacts.
And you'll need to unzip the downloaded file treestyletab-we.xpi.zip manually to extract the XPI package file treestyletab-we.xpi, otherwise you'll see an error about invalid manifest.
Details
Development builds are not signed, so you need to load them by an atypical method. (Please click this section to see instructions.)
There are two methods to try them in your environment:
Go to about:debugging and click "Load Temporary Add-on" button, then choose a XPI file. The development build will be loaded and active until you restart Firefox. Note: don't uninstall the remporarily installed dev build even if you finished a test, because uninstallation clears all configs of TST. Instead you just restart Firefox, then temporarily installed build are unloaded and the previously installed version will go back.
If you want to try it as a regular addon instead of a temporary addon, you need to use Nightly instead of the stable Firefox or Firefox beta. On Nightly, go to about:config and set xpinstall.signatures.required to false. Then you will be able to install such an unsigned XPI file.
Also, you can build a custom development build locally. For example, here are the steps to build an XPI on Ubuntu (native, or WSL on Windows 10):
$ sudo apt install git nodejs npm jq zip
$ git clone --recursive https://github.com/piroor/treestyletab.git
$ cd treestyletab/webextensions
$ make
Steps to build a specific revision (for example bb467286d58b3da90fd1b2e6ee8a8016e3377b97):
$ cd treestyletab/webextensions
$ git checkout bb467286d58b3da90fd1b2e6ee8a8016e3377b97
$ git submodule update
$ make
Then you will see new .xpi files in the current directory. You can install such a development build via about:debugging. Click the Load Temporary Add-on button and choose treestyletab/manifest.json or a built .xpi file.
Extensions that extend TST
TST provides an API for other extensions.
Some extend the behavior of TST's sidebar panel.
See also the list of known helper addons.
Similar projects
There are some similar project by someone not me providing similar features:
Vertical tab bar with tree (and more features)
Tree Tabs
Sidebery
ftt
Vertical tab bar with grouping
Container Tabs Sidebar
Sidebar Tabs
Tab Sidebar
Vertical tab bar without tree or grouping
Tab Center Reborn
Vertical Tabs Reloaded
Vertigo Tabs
Sidebar+
Tabs2List
Listing tabs with a search field
Some extensions provide a pop-up list of tabs with a search field that complements TST:
Tab Manager v2
TabSearch
Tabby - Window & Tab Manager
Tab Master 5000
Power Tabs
Tabs2List: provides not only sidebar panel but a toolbar button with a popup panel also. It has an option to show a search field in the panel by default.
for Google Chrome and Chromium
Sidewise Tree Style Tabs
Tabs Outliner
Treely: Tree Style Tab Manager
Tree Style Tab
for Vivaldi
Tree Tabs
Requests, proposals, or unexpected trouble from bugs
All feedback is handled as GitHub issues.
Please read FAQ below, before you post any new feature request.
Basic project policy
TST is basically designed to be used as a permanently-shown tab management UI, an alternative of Firefox's native tab bar.
To avoid users' confusion, TST respects Firefox's built-in behavior and features regarding the tab bar as possible as it can: tab context menu, gestures, etc., except features impossible to be implemented with regular WebExtensions API.
TST is designed to work with "tree of tabs".
TST's tree is designed to work as an extended memory for your brain. To satisfy this concept, TST is designed to guess the relationship between tabs automatically, from the context.
Better usability for ungrouped flat tabs in a vertical tab bar is an added benefit.
Any feature request unrelated to these points may be rejected, even if many people love it.
For example: session management, search field, detailed focus control of tabs, and so on.
Instead of adding more features, I hope to make TST compatible with other tab-related extensions.
If it is required for better compatibility, I have added public APIs for other extensions, and there are many implementations using this API.
If you need any new APIs, please file API proposals in the issue tracker.
Here is the basic policy about decision to accept or reject feature requests:
If Firefox has the option, TST also should provide similar
Read the full README on GitHub