Primary domain extractor
Reduce domains and URLs to the registered domain with a built-in ~190 entry public-suffix list (com.cn, co.uk, co.jp, com.hk and friends): sub.a.example.co.uk becomes example.co.uk, with optional dedupe and sorting.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Primary domains
One item per line, ready to copy.
Paste domains or links to reduce them
Matches: 0 · Unique: 0
What this tool does
- Collapse a pile of subdomains into registered domains when auditing backlinks or competitors.
- Count how many distinct third-party services a page really pulls in: reduce every host first, then dedupe.
- Clean an allow-list before import so several subdomains of one company collapse into a single entry.
Example
Input
https://a.b.example.com.cn/path?x=1 and https://user.example.co.uk/login, plus mail.google.com and news.example.co.jp.
Output
example.com.cn example.co.uk google.com example.co.jp
com.cn, co.uk and co.jp are multi-part suffixes, so the registered name plus suffix is kept; mail.google.com reduces to google.com.
Frequently asked questions
What is the primary domain of example.com.cn?
example.com.cn — com.cn is a two-label public suffix, so the registered name plus suffix is kept. With a single-label suffix such as .com or .cn the last two labels are kept.
What if my suffix is not in the built-in table?
Unknown suffixes fall back to “the last label is the suffix”, i.e. the ordinary two-label result — nothing errors out.
Does it handle deeply nested subdomains?
Yes. a.b.c.example.co.uk reduces to example.co.uk: everything left of the registered name is dropped.
How is this different from the domain extractor?
The domain extractor keeps the full host name with every subdomain; this tool reduces it further to the registered domain.
Keywords：主域名提取主域名registered domainprimary domain公共后缀公共后缀表根域名域名归约