Reference
WHOIS & RDAP
WHOIS is the classic lookup protocol for registration data. For a TLD itself, IANA's WHOIS returns the delegation record: registry operator, contacts, name servers, and key dates. For individual domains, each registry or registrar runs its own WHOIS service.
What to expect
- TLD lookups
- Reliable and public — this is delegation data, not personal data.
- Domain lookups
- Heavily redacted since GDPR; contact fields are usually privacy-proxied or withheld.
- RDAP
- The structured JSON successor to WHOIS. Same data, machine-readable, with proper access controls. New tooling should prefer RDAP.
How dom4in uses it
We verify registry operators via IANA WHOIS/RDAP rather than scraping. dom4in never republishes per-domain WHOIS data — aggregates only.
Try it: IANA WHOIS for TLDs, or ICANN Lookup (RDAP) for domains (both external).