About Tree Style Tab
Tree Style Tab, often shortened to TST, is the original tab tree for Firefox. According to its README, new tabs opened from the current tab become its children, and branches fold with a click. Results opened from a search page stay grouped, and you can go back to the root tab to find your place.
It is by Piro and has been on Firefox since 2007. The code is on GitHub, with files under MPL 2.0 by default. The listing shows about 141,000 users, a 4.5 rating from about 2,300 ratings and the Recommended badge. Version 4.4.9 arrived on 30 September 2026 and needs a recent Firefox: the manifest sets 139 as the minimum.
The README says the author does not accept donations and that the extension does not automatically collect private data, noting that Firefox Sync may send options and the URLs of tabs you send to other devices to Mozilla's servers. TST is deliberately focused, and feature requests that do not fit the tree idea may be rejected. Pick it if the tree idea appeals. Pick Sidebery if you want bookmarks, history and snapshots in the same sidebar.
Pros and cons
- Organises new tabs under the tab they were opened from, and tabs can be folded away
- Free and open source, with about 140,000 Firefox users
- Author takes no donations and says no private data is collected automatically
- Long track record: on Firefox since 2007, version 4.4.9 in September 2026
- Firefox only
- Stays close to its tree concept, and the README says unrelated feature requests may be rejected
- Can conflict with other add-ons that move tabs, such as Sidebery
Permissions
It asks to read and manage your tabs, tab groups, cookies, container identities, sessions and notifications, and to apply a theme. It does not request access to website content.
