piroor/treestyletab

Tree Style Tab is a Firefox browser extension that replaces the standard horizontal row of tabs with a vertical sidebar where tabs are arranged as a tree. When you open a link in a new tab from an existing tab, the new tab becomes a child of that original tab. Opening further links from the child creates grandchildren, and so on. The result is a branching structure that mirrors the path you took while browsing, making it easy to see what you opened from where. The sidebar lets you collapse a branch by clicking on its parent tab, which hides all its children until you expand it again. This is useful when you have many tabs open on the same topic and want to tuck them away without closing them. You can also drag and drop tabs to rearrange the tree manually if the automatic grouping does not match how you want things organized. The extension is available for free from the Mozilla Add-ons website. Installing it from there gives you a signed, stable release. Development builds for each code commit are also available as build artifacts on the GitHub Actions page, though these are unsigned and require extra steps to load into Firefox, either through the temporary add-on loader in the browser's debugging settings or through Firefox Nightly with signature checking disabled. For developers who want to build the extension from source, the README provides steps using Node.js, npm, and standard Unix tools. The extension also publishes an API that other Firefox extensions can use to interact with the tree structure, and a wiki page lists known companion add-ons that extend its behavior. The README is long and covers a detailed FAQ, project policies, and a list of similar extensions for Firefox, Chrome, and Vivaldi. The full README is longer than what was shown.