Tabbit - Automatic Tab Grouping od The Virtual Panda

Tabbit automatically groups new tabs with the tab that opened them — no manual organizing needed. Click a link, and the new tab joins its opener in a group. Supports two grouping modes, five naming conventions, and per-domain custom rules.

Features
- Group by opening tab (default) or by matching domain
- Name groups by domain, subdomain, full hostname, page title, or leave nameless
- Pretty names for clean, capitalized group titles
- Set a max tabs per group limit
- Auto-ungroup the last tab when a group shrinks to one
- Auto-collapse inactive groups when switching tabs
- Custom rules: assign a name and color to specific domains, with ordered first-match-wins and subdomain matching
- Blacklist domains you never want grouped
- All settings accessible from the toolbar popup with instant save

Requires Firefox 139 or newer (tabGroups API support).