Domain parser (eTLD+1)

Why "the last two parts" is not enough

Taking the last two parts works for example.com, but not for bbc.co.uk, which needs three. Yet parliament.uk needs only two. Nothing in the name tells you which. co.uk is an ending simply because the UK registry sells names under it.

The only reliable way is a list. Mozilla keeps the Public Suffix List for exactly this. Browsers use it, and so does this tool.

Ending, domain and subdomain

The public suffix is the ending that nobody can own directly, like .com or .co.uk. The domain is that plus one more part: the bit someone bought, which browsers treat as "the site". Anything to the left is a subdomain, which the domain owner can create freely.

Shared endings like github.io

The list has two parts. Official endings, like .com, are sold by registries. Private endings, like github.io, vercel.app and s3.amazonaws.com, are run by companies that give out names to different people.

Which one you need depends on your question. To check whether two links belong to the same owner, count private endings, or two strangers' GitHub pages look like the same site. To check who bought a domain, use official endings only, because nobody bought alice.github.io from a domain seller.

Things with no answer

An IP address like 192.168.1.1 is not a domain, so it is not split up. An ending on its own, like co.uk, belongs to nobody. In both cases the tool says so instead of guessing.