About this extension

This is a Firefox add-on which provides 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-triangle shown in a "parent" tab, so you don't need to be suffered from too many visible tabs anymore.
If you hope, 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 lose your browsing trail - if you hope to go back to the original search result, you just have to switch to the "root" tab.
Moreover, you'll treat tree of tabs just as "grouped tabs" for similar topics.

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

Tips:

"F1" key toggles the TST sidebar.
"Tree Style Tab" toolbar button also toggles the sidebar. If it's unnecessary, you can remove it from the toolbar.

Helper addons:

There are some addons extending usability of TST's sidebar.

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.

Latest information is available at the repository.

Developer comments

## Similar projects

*Tree Tabs:
Cross-browser, more powerful faatures, and high customizability.
(One large difference between TST is: the design strategy.
TST is aimed to keep it simple and work together with other addons as possible as it can.)
* Tab Center Redux:
Vertical tab bar without tree.
* sidebarTabs:
Vertical tab bar with grouped tabs.

Some Google Chrome extensions made by someone not me also provide similar feature.

* Sidewise Tree Style Tabs
* Tabs Outliner
* Treely: Tree Style Tab Manager
* Tree Style Tab

## Public API for other addons

For addon authors, Tree Style Tab provides public API. If your addon provides extra context menu items for context menu on tabs, you can easily support TST's context menu with small changes. For more details, see the API document.

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Release notes for 3.5.34

3.5.34 (2020.10.22):

Create group for tabs opened from a pinned tab correctly, even if "no control" is chosen for the insertion position of new child tabs. (regression on 3.5.33)

3.5.33 (2020.10.20):

Add an explicit choice to open new child tabs at the position next to the recently opened child or the opener parent tab, like Firefox does with the preference browser.tabs.insertRelatedAfterCurrent=true.
Add an expert option to insert new child tabs at the top or the end, when they are dropped onto a parent.
Add some expert options to configure checkbox status of group tabs created for each context.
Simulate Firefox's focus control behavior like the combination browser.tabs.insertRelatedAfterCurrent=true and browser.tabs.selectOwnerOnClose=true more correctly. (On old versions the parent tab was unexpectedly became the successor of a closed child tab even after manual focus changes.)
More stabilize behaviors around auto-grouping of tabs opened from a pinned tab.
Don't reload tab inifinitely when a URL is loaded on a group tab (it was originally reported as the bug 1671500.)
Update ru locale by wvxwxvw. Thanks!

3.5.32 (2020.10.11):

Save "Warn me when I attempt to close multiple tabs" checkbox state correctly for the confirmation dialog about closing multiple tabs via the closebox.
Handle tabs which are immediately opened and closed more safely. It will improve compatibility with other tab addons which reopen new tabs, e.g. Temporary Containers.
Handle closing of multiple tabs more safely for already closed tabs.
Scroll the tab bar to expanded tree. (regression on recent versions)
Scroll the tab bar to expanded tree even if animations are disabled.
Restore closed tree with their original order and tree structure more correctly.
Keep and restore checkbox state of group tabs correctly. (regression on recent versions)
Fill the user styles field with imported configs immediately.
Accept ext+treestyletabi:sidebar as an alias of ext+treestyletab:tabbar.

3.5.31 (2020.10.4):

Restore group tab title correctly. (regression on 3.5.30)

3.5.30 (2020.10.4):

Add ability to specify arbitrary title for the sidebar page with the parameter title, like ext+treestyletab:tabbar?title=.... This is for better compatibiliy with helper addons using TST's sidebar page e.g. Tree Style Tab in Separate Window.
Load sidebar page with the chosen builtin theme immediately when it is loaded via ext+treestyletab:tabbar URL. This is for better compatibiliy with helper addons using TST's sidebar page e.g. Tree Style Tab in Separate Window.
Apply browser theme and user styles to the sidebar page more safely when the builtin theme information is not specified via the URL parameter. Thank you Lej77!

3.5.29 (2020.10.4):

The "Load from File" button for the user styles now allows you to choose images and embed them as data: URIs.
The user styles input field now accepts drag and drop of files (but this new behavior is available only when the options page is opened in a separate tab instead of embedded in the addons manager, due to the bug 1408756).
Reopen new tab from external application with specific containers correctly.
Never reopen a new tab with a container inherited from the current tab or the parent tab, when the tab is opened with non-default container.
Never show needless vertical scrollbar in group tabs even if there are too many tree items.
Never draw tree of tabs multiple times in a group tab. (regression on recent versions)
Support two digits year with the placeholder $SHORT_YEAR% for names of generated bookmark folders.
Update ru locale by wvxwxvw. Thanks!

3.5.28 (2020.9.29):

Better visibility of active tabs and closeboxes on the high contrast mode.
Fix regressions on 3.5.24 around auto-correcting of tabs order after multiple opened tabs.
Fix wrong successor tab control around child tabs and their closed opener parent tabs: the next sibling of a closed child active tab will become active instead of the parent tab.
Initialize restored group tabs more certainly.
Search text dropped onto the sidebar with the default search engine correctly.
Add regular choices for drag and drop options to prevent detaching of dropped tabs to a separate window.
Add ability to control container of new tabs from three options: no inheritance, inherit from the current tab, or inherit from the tree parent.
Show throbber with the color same to tab labels on a dark theme.
Remove needless underline of tab labels on the "Sidebar" theme.
Set "Plain" as the default theme on Windows and Linux correctly.
Fix wrong behaviors of "All Configs" UI: apply imported configs to options UI immediately and treat decimal values as valid for some numeric options.
Update ru locale by wvxwxvw. Thanks!

3.5.27 (2020.9.6):

Reduce more visual motions when they are reduced by platform configs.
Add an expert option to activate animation effects regardless platform configs.
Update de locale by SammysHP. Thanks!

3.5.26 (2020.9.3):

Deactivate animation effects globally when they are reduced by platform configs.
Deactivate throbber animation when animation effects are reduced by platform configs.

3.5.25 (2020.9.2):

Optimize performance around the "lock scroll position" behavior.
Add "Ungroup Tabs" context menu command.
Open the changelog from the update notification popup.
Update ru locale by wvxwxvw. Thanks!
Fix typo in Enghlish locale by reaverxai. Thanks!

3.5.24 (2020.8.28):

Simulate "lock scroll position of the tab bar while middle tabs are closed via mouse operations" behavior of Firefox's native tab bar.
Shrink the width of the confirmation dialog for closing tabs with very long titles.
Detect a tab is opened from a bookmark more certainly, even if its hostname starts with "www."

3.5.23 (2020.8.26):

Drop support for some built-in themes: "Vertigo" and "Mixed". They can be alternated with user styles.
Simulate appearance of close boxes in Firefox's native tabs more, for hover and active state.
Close the tab by click on the close box, even if the cursor has moved out from the close box and went back while the button is pressed, like close boxes in Firefox's native tabs.
Set default color of icons for the "No Decoration" theme.
Save cached tree state as a metadata related to each window instead of individual tab.
Attach tabs opened from dropped links to existing tree based on their position. (regression on recent versions)
Update ru locale by wvxwxvw. Thanks!

3.5.22 (2020.8.12):

Shift-click to multiselect tabs between the clicked tab and the active tab correctly, even if it happens after focus move from outside of TST.
Restore closed tabs with their correct old position even if their visibility was switched by something other addons like Simple Tab Groups.
Save very large user style rules more safely.

3.5.21 (2020.8.8):

Apply user style rules to group tabs again. (regression on 3.5.20)
Update ru locale by wvxwxvw. Thanks!

3.5.20 (2020.8.7):

Use the SVG icon insetad of the PNG icon on all situations.
Apply system colors by default only on Linux with non-dark platform theme.
Extend the maximum size of the user style rules from 8KB to 48KB.
Notify new features with a desktop notification instead of an annoying tab.

3.5.19 (2020.8.4):

Use the toolbar color defined in the theme as the background color of each tab surfaces.
Accept themes with colors defined in various formats hsl(), hsla(), and their variations.

3.5.18 (2020.8.4):

Safely restore tree for reopened tab even if its old parent was already closed. (regression on 3.5.16)
Safely restore tree for reopened tab on the "Fix up tree structure with visible tabs automatically" mode. (regression on 3.5.17)

3.5.17 (2020.8.3):

Undo closed tab at its correct old position, even it it was restored as a hidden tab on the startup.
Update ru locale by wvxwxvw. Thanks!

3.5.16 (2020.8.1):

Drop support for some built-in themes: "Metal" and "Plain Dark". They can be alternated with user styles.
Fix too dark color for active tabs from combinations of the Dark color scheme and a bright theme.
Apply a workaround for a problem: unreadable text color on the "High Contrast" mode of Windows 10.
Respect tiling option specified by the browser theme, otherwise expand the background image as an un-repeatable when the aspect ratio of the image is wider than 4:1.
Apply system colors on Linux environments by default again.
Allow to attach restored hidden tab to other hidden tabs.
Suppress errors around dragging of non-tab data.

3.5.15 (2020.7.30):

Expand the background image cited from the browser theme to cover the sidebar area, instead of repeating.
Don't attach restored tab to its old hidden parent when TST is configured to fix trees based on visible tabs.

3.5.14 (2020.7.29):

Confirm to close tabs via context menu commands on the sidebar correctly. (regression on recent versions)
Always apply the "Photon" color scheme on Linux environments.
Always apply browser's theme to the sidebar (on Mixed, Plain and Vertigo).
Keep the tab in the root level, when a tab is moved or opened before a root tab. This improves compatibility with the Facebook Container.
Flexible width input field in the bookmark properties dialog.
Update ru locale by wvxwxvw. Thanks!

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