Auto-group

Build a list of rules — domain, hostname, URL, host + path or title, matched by contains / is exactly / starts with / regex — each pointing at a named, coloured tab group. Rules are checked top to bottom and the first match decides a tab's group; a tab that matches nothing is left alone.

Turn on "Automatically group new tabs as they open" to have it happen live, or leave it off and press "Group tabs now" when you want it. Either way it only ever adds a tab to the group its rule points at — it never pulls a tab out of a group you put it in by hand.

Also in this release

• "Group tabs (saved rules)" is on the toolbar menu and on a tab's right-click menu. It ships without a keyboard shortcut; assign one from about:addons, gear icon, Manage Extension Shortcuts.
• The popup's tab bar was refitted for the sixth panel so no label is cramped.