Subdomain Extractor

Paste a URL or bare hostname and walk every label back to its registrable domain (the “eTLD+1” — for example.co.uk the eTLD+1 is the whole three-label string, because co.uk is a single public suffix). The tool ships a curated lookup of 80+ multi-part public suffixes (.co.uk, .com.au, .co.jp, .com.br, .com.tr, …) so it gets api.v2.blog.example.co.uk right without pulling in the full PSL. Bulk mode below for one-per-line lists, with copy as TSV. IP literals (IPv4 and IPv6) are detected and flagged. Pure client-side, no upload, no tracking.

A URL (with scheme) or a bare hostname. Trailing dots are stripped (FQDN form).

Try:
one URL or hostname per line · up to 200
0 lines
How the eTLD+1 split works
  • A domain name is a chain of labels separated by dots: api.v2.blog.example.co.uk has six labels — api, v2, blog, example, co, uk.
  • The public suffix is the rightmost chunk you can’t register through a normal registrar. uk by itself is a public suffix; co.uk is also a public suffix because you register the third-level name, not the second-level.
  • The eTLD+1 (effective top-level domain plus one) is the public suffix plus one label to its left — that’s the smallest unit you can actually register. For api.v2.blog.example.co.uk the eTLD+1 is example.co.uk.
  • Everything left of the eTLD+1 is the subdomain path. The tool returns them as a list (longest first) and as a list of progressively-shorter subdomains: api.v2.blog.example.co.uk, v2.blog.example.co.uk, blog.example.co.uk.
  • The tool ships a curated lookup of 80+ multi-part public suffixes (.co.uk, .com.au, .co.jp, .com.br, .com.tr, .com.tw, .co.in, …). Single-label TLDs (.com, .net, .org) need no entry — the last label is treated as the TLD.
  • For unknown multi-part suffixes the tool falls back to “TLD = last label”, which is correct for the rest of the namespace but may mis-classify niche multi-part suffixes. The output surfaces the detected kind (“single-label TLD” vs “multi-part suffix”) so you can sanity-check.
  • IPv4 and IPv6 literals are detected and reported separately — they have no DNS labels to walk.
  • The full IANA / Mozilla Public Suffix List is intentionally NOT bundled; the 80+ curated entries cover the suffixes you’ll actually hit in everyday URLs. If you need a missing suffix added, open an issue on the repo.
  • Nothing leaves your browser. All parsing runs locally.