This is a Firefox add-on which provides the ability to operate tabs as "tree".

New tabs opened from the current tab are automatically organized as "children" of the current. Such "branches" are easily folded (collapsed) by clicking on down on the arrow shown in the "parent" tab, so you don't need to suffer from too many visible tabs anymore. 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, you'll open each search result link in new child tab. For more details you'll also open more descendant tabs from them. 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, you'll treat a tree of tabs just as "grouped tabs" for similar topics.

Anyway this addon just provide uncolored "tree" feature. Please enjoy as you like!

• 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 TST sometimes drops outdated versions of Firefox, but you may find out old packages supporting the dropped versions of Firefox.
• For more older versions of Firefox, Waterfox, or Palemoon, Classic Add-ons Archive possibly contains legacy packages of TST.

There is an automated build based on the latest source code. Builds for each commit are avilable at "Artifacts" of the CI/CD action.

$ sudo apt install git nodejs npm
$ git clone --recursive https://github.com/piroor/treestyletab.git
$ cd treestyletab/webextensions
$ make

$ cd treestyletab/webextensions
$ git checkout bb467286d58b3da90fd1b2e6ee8a8016e3377b97
$ git submodule update
$ make

TST provides an API for other addons. Some addons provide extended behavior to TST's sidebar panel:

• Multiple Tab Handler allows you to select multiple tabs with long-press on tabs. It also allows you to close mutiple tabs with long-press on the closebox on tabs.
• TST Bookmarks Subpanel allows you to show a small "Bookmarks" sidebar panel below tabs in the TST's sidebar.
• TST Active Tab in Collapsed Tree shows a small tab on a collapsed tree as an alias for the last active tab under the tree.
• TST Lock Tree Collapsed allows you to lock arbitrary trees as collapsed. (This was a built-in feature on TST 3.3.0-3.3.6, and now separated.)
• TST Tab Drag Handle provides a small tooltip on tab labels to start dragging of tabs for specific operations. (This was a built-in feature on TST 2.6.0-3.3.6, and now separated.)
• TST Open Bookmarks as Partial Tree allows you to open only some bookmarks in a folder as a partial tree. Moreover, it also provides ability to open tree of container tabs from bookmarks.
• TST-MiddleClick allows you to run "undo close tab" or "close currently active tab" command on middle click on the sidebar.
• Tree Style Tab Mouse Wheel allows you to switch active tab by wheel scrolling.
• Tab flip for Tree Style Tab allows you to move focus to the tab previously focused, by clicking on the active tab.
• Tree Style Tab Focus Preceding Tab on Close focuses the previous tab instead of the next tab when a tab is closed.
• Tab Unloader for Tree Style Tab allows you to unload tabs by clicking on them in the sidebar.
• Move unloaded tabs for Tree Style Tab allows you to move tabs in the sidebar without them becoming active.
• Tree Style Tab in Separate Window allows you to open the Tree Style Tab sidebar page in a new window.
• Auto Tab Discard supports the fake context menu in the Tree Style Tab sidebar.
• UnloadTabs supports the fake context menu in the Tree Style Tab sidebar.
• Bookmark Tree for Tree Style Tab allows you to bookmark and restore trees.
• TST Hoverswitch allows you to switch tabs by hovering over them.
• TST Colored Tabs gives custom background color for tabs based on their domain.
• Add Last Active Class To Tab helps you to give custom appearance for the "previously active tab".
• TSTのタブを閉じるボタンの挙動を変更 (tst-change-close-tab-button-be) allows you to close the parent and its all descendants with a middle click on the closebox of a parent tab, whether the tree is expanded or collapsed.

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
  • Tab Center Redux
  • Vertical Tabs Reloaded
  • Vertigo Tabs
  • Sidebar+
  • Tabs2List
• Listing tabs with a search field

  There are some addons providing a popup panel to show a list of tabs with a search field corraborative with 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
  • Tree Style Tab for Chrome
• for Vivaldi

  • Tree Tabs

All feedbacks are handled as GitHub issues. But please read FAQ below, before you post any new feature request.

• TST is basically designed to be used as an 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 around the tab bar - tab context menu, gestures, and so on.
• And, of course 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 relation of tabs automatically, from the context.
  • Better usability around ungrouped flat tabs in a vertical tab bar is out of purpose.

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 built-in features, I hope to make TST compatible with other tab related addons. If it is required for more better compatibility I add public APIs for other addons, and actually there are some implementations using this API.

If you need any new API, please file API proposals to the issue tracker.

• Support for Pale Moon, Waterfox, and other Firefox forks

  Please use a forked version of TST for Pale Moon instead. There is also a forked version for Waterfox Classic. TST is designed for latest release of Mozilla Firefox (*Please see also the strict_min_version information in the install manifest to know the minimum supported Firefox version), and other applications forked from Firefox are not supported.

  "Waterfox Current" looks based on Firefox ESR68 and you can install TST 2.0 and later to it. However "Waterfox Classic" based on Firefox 56 is never supported.

• Support for Google Chrome and other Chromium based browsers

  TST can't be ported to Chrome because it depends on some Firefox specific API like sidebar, so it needs to be re-implemented completely. Sorry but I won't re-implement TST as a Chrome extension by myself because I still use Firefox. (But there are some alternatives developed by someone not me.)

• How to hide the top tab bar (horizontal tab strip)?

  As a workaround, you need to do it by creating a userChrome.css. But please remind that such an usage is not recommended by the original author of TST, because TST doesn't cover full features of the native tabs due to restrictions of WebExtensions API so some tab features become inaccessible.

• Support for horizontal tab bar

  It is impossible. TST 2.0 and later are implemented as just a sidebar panel, so there is no chance to provide horizontal version.

• Better support for non-indented vertical tabs

  It is out of purposes of "Tree" Style Tabs. I recommend you to use other addons providing vertical tab bar without tree instead.

• Better context menu on tabs

  Full featured, expanded outside of the sidebar, accesskeys, and so on, is available on Firefox 64 and later.

  However, please note that some features are still unavailable due to restrictions of WebExtensions API, for example "Send Tab to Device".

• I don't need automatically organized tree, instead I just want to organize tree by myself

  You can deactivate TST's automatic tree organizing behaviors, by some secret preferences:

  1. Go to TST's configuration.
  2. "Development" section.
  3. Turn on the checkbox "Debug mode". Then all internal configurations are listed.
  4. Turn off the checkbox "autoAttach".
  5. Turn off the checkbox "syncParentTabAndOpenerTab".

  After that TST never attach new tabs to existing tree automatically.

  If you want to drag multiple tabs at once to organize tree, Shift/Ctrl-click to select multiple tabs (and Multiple Tab Handler for more feature) will help you.

• Adding new minor (trivial) options more and more

  I won't increase number of configurations inifinitely, instead I hope to reduce them. High customizability for details of features is out of TST's purpose. I want to provide only very required options which are truly un-omitable. Too many optional features would kill this project, because they would cloud the important concept of TST and would bring together people who don't like my core vision about TST. Instead, sorry but please fork this project and modify it for your use case.

• Adding new options to control where new tabs are opened from links or bookmarks

  In most cases - subjectively 99%, new tabs from links may be related to the source tab, and tabs from bookmarks may not be related to the current tab. For other rare cases - if you want to open the link in new sibling tab, or you want to open a bookmark as a child tab of the current, then you can do it by dragging a link or bookmark and drop it onto a tab or between tabs. Natural operations for GUI objects shoud be optimized for most major usecases.

  Too high customizability for such rare usecases would make just you happy, but others including me won't - they are just confused that "why are there so many choices to make?"

• Adding new context menu command to go to the options page

  Do you use the toolbar button of TST itself? Then you can go to TST's options page directly from the context menu on the button. Firefox provides a "Manage Extension" command globally at the context menu on toolbar buttons provided by addons. Moreover, TST privately provides more commands like the options dialog at the menu for a shortcut.

  On the other hand, I'm negative to provide a command like "TST Options" at the context menu on tabs, with some reasons:

  • The command is fundamentally unrelated to the context: "what command do you want to invoke for the tab?"
  • If you need to change TST's options too frequently on your daily use, something wrong. For example, a failure auto-detection of TST for your action's context. I believe that such a problem should be fixed on TST side like improvements of auto-detection, instead of providing easy way for workaround.

  If you really need to access TST's options page very frequently due to some reasons, as a workaround you can bookmark the page with the URL ext+treestyletab:options. It allows you to open the options page in a tab.

• How to customize tab context menu?

  You can do it with the userChrome.css. There are some instructions about activatiton of the userChrome.css on recent versions of Firefox and style rules to hide specific context menu items.

• Auto hide of the sidebar

  Due to limitations of WebExtensions APIs, it is impossible. (But there is a workaround based on userChrome.css.)

  WebExtensions only allows to toggle visibility of the sidebar for limited keyboard shortcuts or the toolbar button. Other arbitrary timing are disallowed, including mouseover and long-press of a key.

• I want to use "Bookmarks" sidebar panel parallelly with TST's tabs

  TST Bookmarks Subpanel is now available for TST 3.1.0 and later. It provides a cloned version of the "Bookmarks" sidebar panel below TST's tabs.

• High-power management of tree, like sorting child tabs, auto-modification of tree, renaming of tabs, and so on

  I believe that generally "tree of tabs should be a visualized history of web browsing", because they are built on relations where you came from. Possibly such a tree is facially chaotic, but it just mirrors your actual footmarks, so you'll easily find out where is the target tab based on a map in your mind. Moreover, those relations themselves may let you recall forgotten idea you thought while you were browsing those tabs.

  On the other hand, sorted tabs based on URLs or something will be beautiful - but that's all. Such sorted tabs won't help me - I'm very forgetful. In other words, I just need something which memorizes my chaotic mind as-is.

  By the way, my another addon Multiple Tab Handler will help you if you frequently modify tree by drag and drop. It provides ability to select multiple tabs by Ctrl-Click or Shift-Click and you can drag selected tabs at once.

• Configuration UI to change appearance of tabs in the vertical tab bar, for example, color, height, visibility of the scrollbar, transparency of tabs, and so on

  There is a plan to implement an input field to write custom CSS rules, so it will work like as userChrome.css. See the code snippets and details of inspection for the sidebar contents.

• I cannot drop tabs to the bookmarks toolbar to create bookmarks. (#2033)

  In short: shift-dragging of tabs will allow you to drop tabs to the bookmarks toolbar. Otherwise TST Bookmarks Subpanel possibly helps you.

  From a change introduced at the bug 1453153 (affects on Firefox 63 and later), now Firefox doesn't allow addons to provide ability to do "creating bookmarks (or links) by drag and drop of tabs" and "detach a tab to a new window by dropping it outside of the window" in same time - those functionailities are quite exclusive. (For more technical details, see my comment at the issue #2033.)

  Thus, now TST provides two different effects to gestures:

  • Dragging tabs to out of the tab bar: detach dropped tabs to a new window. You cannot drop tabs to the bookmark toolbar.
  • Shift-dragging tabs to out of the tab bar: create links to the desktop from dropped tabs. You can drop tabs to the bookmark toolbar to create bookmarks.

  You can switch these behaviors. Please go to the "Drag and Drop" section of TST's options page. (By the way, TST Bookmarks Subpanel's small Bookmarks panel always accept drag and drop of TST's tree without such modifier keys.)

  For more preference, you can use a small drag handles with a helper addon: they will appear when the cursor is hovering on left edge (or right edge for inverted appearance) of a tab for a while. You can start dragging of the tab from one of handles, with specified effect for each without any modifier key.

• I don't want to see the next tab is focused before the previous tab is focused, when I close a last child tab. (#1838)

  In short: you need to wait for Firefox 64.

  There are two cases when the current tab is going to be closed.

  1. The tab is closed by TST itself, by clicking the closebox of a tab in the sidebar, or choosing "close tab" command from the fake context menu in the sidebar.
  2. The tab is closed by Firefox itself or other addons, in other methods (Ctrl-W, clicking the closebox of a tab in the horizontal tab bar, etc.)

  TST can focus to the previous tab directly before the current tab is closed, only for the 1st case. On the other hand, for the 2nd case, TST cannot inject any operation before the tab is closed, instead just a "tabs.onRemoved" event is notified after the focus was actually moved by Firefox. So logically TST cannot prevent the "the next tab is unexpectedly focused" behavior for the 2nd case.

  Moreover, if TST always control focusing of tabs for the 1st case, it will conflict to Firefox's browser.tabs.selectOwnerOnClose=true behavior or other addon's behaviors. My development policy about TST is: being compatible to Firefox's native features and other addons, thus I won't introduce such a behavior breaking compatibility with others.

  However Firefox 64 will have some new WebExtensions APIs about this point. After those APIs land, TST will be updated to use them and you'll never see the "next tab is unexpectedly focused" behavior anymore.

• How to donate to this project?

  Thanks, but sorry, I have no plan about any donation from some reasons. The biggest reason is: because I want to keep me as the prime user of this project. I want to keep having a privilege to say "no" about requests that do not match my vision. My hands are already full to maintain this addon for my use case. (Of course I know that donation is not payment, but I'm afraid that I would think about voices from people who did donation more seriously and it would unconsciously conflict with my policies.)

  And, I'm afraid of social undermining also.

  Any other contribution to this project is welcome - translation, debugging, triaging of issues, and more. If you have fixed a bug you met, please send a pull request - I'll merge it. If you have different plans about TST, please fork this project freely for your purpose, if needed.