Tab Grouper by Subdomain by Jack

Tab Grouper by Subdomain automatically organizes your browser tabs into Firefox’s native tab groups based on their domain and subdomain — so you don’t have to.

How it works:
Every tab is grouped by its hostname. The group name uses the leftmost part of the URL:

• mail.google.com → group “mail”
• drive.google.com → group “drive”
• grafana.mms.company.com → group “grafana”
• github.com → group “github”
• 192.168.1.1 → group “192.168.1.1”

Tabs with the same full hostname land in the same group. Different subdomains get their own group.

Features:
• Automatic grouping — tabs are grouped the moment they open or navigate to a new URL
• Smart colors — adjacent groups never get the same color
• Remembers custom names — rename a group and it sticks for that domain forever
• Capitalize toggle — optionally capitalize group names (e.g. “Github” instead of “github”)
• Respects existing groups — manually created groups are not overridden
• Ignore “www” prefix — treats www.site.com the same as site.com
• Collapse toggle — optionally start new groups in collapsed state
• Manual controls — “Group New”, “Regroup All”, and “Ungroup” buttons in the popup
• Reset custom names — clear all remembered renames with one click

Settings available from the popup:
• Enable/disable the extension
• Toggle auto-grouping for new tabs
• Collapse new groups automatically
• Ignore “www” prefix
• Capitalize group names
• View and reset custom group name mappings

Privacy:
This extension does not collect, store, or transmit any personal data. All settings and custom names are stored locally using browser.storage.sync. No analytics, no tracking, no servers.

Permissions explained:
• tabs — needed to read tab URLs for grouping
• tabGroups — needed to create and manage tab groups
• storage — needed to save your preferences and custom group names

Requires Firefox 131 or later (native tab groups support).

Open source. Contributions welcome.