4.3.1

4.3.1

• Fix breakage of custom dialogs (confirmation of closing tabs, bookmark creation, and others) on recent Firefox.
• Reduce needless handling of changed configs while drag-and-drop operations.
• Show duplicated tabs correctly even if the source tab has discarded state.
• API: get-tree and get-light-tree calls now return results correctly if tabId or tabIds are used.

4.3.0

• Support presentation of split view on Firefox 149 and later. (Management commands except "Reverse Tabs" are not available yet due to restrictions of WebExtensions API.)
• Simulate "Copy Link(s)" context menu command of Firefox 150 and later.
• Add "Copy Tree as Links" and "Copy Descendant of Tree as Links" context menu commands corresponding to Firefox's "Copy Link(s)".
• Optimize tree restorations triggered by "Undo Close Tab" operations. (by tkng, thanks!)
• Avoid unclickable Web contents problem after TST is unloaded.
• Open dropped link in new tab with tab group if it is dropped onto a grouped tab or a group header.
• Collapsed tab groups are now automatically expanded while dragging.
• Brush up styling and text alignment in tabs and tab groups globally. (by tcbbd, thanks!)
• DOM structure of tabs is changed to support split view - now a tab-item may contain multiple tab-item-substance elements. CSS customizations may need to be updated for the new DOM structure. See also a migration guide.

4.2.12

* Stabilize and optimize moving of multiple tabs with tree structure, especially across windows. ([by tkng](https://github.com/piroor/treestyletab/pull/3880), thanks!)
* Add "Unload this Tree" and "Unload Descendants" context menu commands corresponding to the native "Unload Tab".
* Allow to create new native group by dropping tabs onto any areas of another tab simply, with pressing Shift key. (Without shift key, you need to drop tabs onto the head area of another tab to create new group.)
* Reconstruct option to set UI direction of the sidebar as Regular/Inverted instead of Left/Right. "Regular" always works similar to Firefox's native vertical tabs.
* Show confirmation dialog correctly for closing multiple tabs in a fullscreen browser window on macOS.
* Show tab previews in tab-hover tooltip again. (regression on 4.2.8)
* Fix misdetection of drop position of tabs after tabs are rearranged. (regression on 4.2.7)
* Duplicate partially dragged tree at the dropped place correctly.
* Fix mis-ordering of multiselected tabs moved by drag and drop.
* Fix mis-sizing of tab bar boxes after extra contents are inserted via API.
* Fix too narrow width of group labels in the Photon theme.
* Don't show nonsense "+0" label for collapsed tab groups with no other member.
* Suppress needless animation effects when items are scrolled into the view.
* Expand tab group automatically when a collapsed tree in the group is expanded. You can deactivate this new behavior with a new expert option under the "Tree Behavior" section.
* Don't mistreat dropped URL as a native tab drop.
* Hide UI elements internally used and should not be exposed to users, even if the background screen of the sidebar has transparent color.
* Detect "head" area of the drop target tab correctly on RLT environment, to create new group by drag and drop.
* Fix wrong alignment of tab group labels on inverted mode.
* Fix wrong text direction and alignment of tab labels with LTR title on RTL environment.
* Suppress uncaught errors caused by already closed tabs or windows, around mouse operations, successor tab operations and caching of tree information.
* Fix links to MDN documents from changelogs. ([by theluckystrike](github.com/piroor/treestyletab/pull/3879), thanks!)

4.2.11

• Custom tabs for grouping (ext+treestyletab:group) are available again on Firefox 150+ which never supports injecting of scripts to addon-hosted contents due to the bug 2011234. See #2356 in Sidebery for more details of affections of the bug.
• Fix wrong order of header and counter items for collapsed native tab groups after native groups are moved. (regression on 4.2.10)
• Stabilize tree restorations based on tree information stored to each tab (by tkng, thanks!)
• Don't leave phantom group and collapsed members counter after a collapsed native group is closed.
• Keep tree structure on detaching all children on some situations (including #3858 by tkng, thanks!)
• Suppress confirmation about closing multiple tabs if the number of closing tabs are smaller than the threashold 25 (same to the default value of browser.sessionstore.max_tabs_undo. If you changed it, please synchronize the threashold to the value of the option) like Firefox does, even if the confirmation is enabled. (by tkng, thanks!)
• Many performance improvements with optimizations and fixed leaks (#3854, #3865, #3857, #3870, #3872 and #3876 by tkng. Thanks!)
• Many cleanup of codes for future maintainability (#3853, #3855, #3856, #3859, #3860, #3862, #3863, #3864 and #3866 by tkng. Thanks!)
• Reduce dead codes around custom event handling and needless exports, for better maintainability.

4.2.10

• Show new tab action selectors on both side of the new tab button correctly, when both container selector and relation selector are active. (by bb010g, thanks!)
• Restore tree of tabs certainly on crash recovery and/or manual restoration of the previous session. (by tkng, thanks!)
• Fix handling of closed tree restoration: multiple tabs of a closed tree are now restored with single action correctly. (by tkng, thanks!)
• Many performance improvements with optimizations (#3831, #3836, #3837, #3838, #3839, #3843, #3847 and #3848 by tkng. Thanks!)
• Some performance improvements with optimizations around reduced reparsing of JSON strings while dragging and reduced reflowing.
• Apply and update auto-sticky state of tabs correctly, even if they are specified by other addons. (by tkng, thanks!)
• Update custom tooltip text more correctly. (by tkng, thanks!)
• Many cleanup of codes for future maintainability. (#3832, #3833, #3835, #3844, #3849, #3851 and #3852 by tkng. Thanks!)
• Suppress errors from handling of successor tabs when a tab is closed before the successor information is updated.

4.2.9

Fix some possible memory leaks around closed windows, tabs, and removed elements.

4.2.7

• Fix ability to drop items before the first tab when there is no pinned tab.
• Increase the default delay to show the drop area for tabs to be pinned (500ms to 740ms: you can configure it with a secret option pinInteractionCueDelayMS).
• Prevent grayed favicons of restored tabs in the first window restored from the previous session explicitly.
• Treat discarded tabs as pended correctly, even if restoration from cache is failed.
• Hide "unload tab" context menu command for already discarded tabs, like Firefox does.
• Reduce needless re-rendering of virtually scrolled tabs when pinned tabs are scrolled.
• Update en locale to fix a typo by purplnecropanda. Thanks!

4.2.6

• Add ability to pin/unpin tabs by drag and drop. Now you can drop pinned tabs below/between unpinned tabs, and unpinned tabs above/between pinned tabs. This simulates behaviors of tab dragging on Firefox's vertical tabs.
• Disallow to set the height of the pinned tabs area smaller than the height of a pinned tab.
• Use label text for the "new tab" command in the context menu on tabs same to Firefox's native one, if possible.
• Show dropdown list in options with colors more easy-to-read, on the dark color scheme.
• Expose the expert option to control the position of the context menu popup for native tab groups.
• Update ja locale by tkng. Thanks!

4.2.5

• Support ability to keep the active tab in a collapsed group visible on Firefox 142 and later.
• Prevent to show simulated tab preview panel on non-tab items.
• Prevent "shaking" of pinned tabs when the height of the pinned tabs area is narrower than a tab.
• Restore ability to drop dragged items to the blank area of the tab bar. (regression at 4.2.0)
• API: Fix container assignment for extra tab contents below tabs by emmanuel-ferdman. Thanks!
• Update uk locale by Taron-art. Thanks!

4.2.4

• In-content panels (tab groups menu and tab previews) handle events correctly. (regression at 4.2.3)
• Never mix reactions for custom dialogs even if multiple dialogs are shown at a time.
• Update uk locale by Taron-art. Thanks!

4.2.3

4.2.3 (2025.6.23)

• Context menu commands now works even if it is opened on a blank space (by joanbm. Thanks!)
• Add an expert option to activate/deactivate native tab groups management UI (corresponding browser.tabs.groups.enabled of Firefox itself).
• Scroll pinned tabs container when an out-of-view pinned tab become active.
• Remove dragged tabs from their group when they are dropped before a group header explicitly.
• Don't create needless new group when a last member is dropped before the next another group but the tab is not moved actually.
• Disallow to resize pinned tabs area size larger than required.
• Unblock user operations correctly after drag-and-drop of tabs across windows. (regression at 4.2.0)
• Treat focused or active tab as the context tab if the context menu is opened via the keyboard (ex. Shift-F10 on Windows).
• Accept more cases of dropped native tabs.
• Delete obsolete option to deactivate using of tab multiselection API.