RDAP (Registration Data Access Protocol, RFCs 7480-7484) is the modern replacement for WHOIS. It uses HTTPS + JSON + structured data + optional authentication — everything WHOIS lacks.
Query Format
GET https://rdap.verisign.com/com/v1/domain/example.com
Accept: application/rdap+jsonImprovements Over WHOIS
| Aspect | WHOIS | RDAP |
|---|---|---|
| Transport | plain TCP port 43 | HTTPS |
| Format | free-text | JSON |
| Auth | none | OAuth / TLS client cert |
| I18N | ASCII-only | Full Unicode |
| Rate limits | unspecified | HTTP 429 responses |
| Referrals | server-defined | RDAP bootstrap file at IANA |
Bootstrap File
IANA publishes a JSON file at https://data.iana.org/rdap/dns.json mapping every TLD to its authoritative RDAP endpoint. RDAP clients read this first, then query the correct server directly — no whois.iana.org referral chain needed.
Adoption
All gTLDs are RDAP-mandated as of 2019. ccTLDs vary. Most modern tools (including whois on macOS) will query RDAP first and fall back to WHOIS if RDAP is unavailable.
Related
Check the WHOIS glossary entry, the EPP glossary entry, and the TLD entry.