Merge Subdomains

With Group Tabs by Domain, puts tabs from the same site in one group even when they're on different subdomains. gist.github.com joins github.com, and developer.apple.com joins apple.com.

Why use it

Some sites spread one product over several subdomains, like mail.google.com and docs.google.com, or old.reddit.com and www.reddit.com. Off, each subdomain gets its own group, which can leave you with a handful of small groups for one site. Turn this on if you think of those as one site. Leave it off if you want docs.example.com kept apart from example.com.

Turn it on

Open Dia → Settings → Patches → Group Tabs by Domain and, under Options, switch on Merge Subdomains. Or run:

diatweaks enable groupTabsMergeSubdomains

Needs

Group Tabs by Domain. Settings greys out this switch until that's on.

FAQ

How does it know what the site is?

It keeps the last two parts of the address, so news.example.com becomes example.com. Under a two-letter country ending with a common second part, like .co.uk or .com.au, it keeps three, so news.bbc.co.uk becomes bbc.co.uk. It's a short rule rather than the full list browsers use, so the odd site may group differently from what you expect.

Why aren't my github.io sites merged?

On sites like github.io, vercel.app, netlify.app, pages.dev and blogspot.com, each subdomain belongs to someone else, so each one stays its own site.

What about addresses like localhost or 192.168.1.10?

They're left as they are.