RDAP (Registration Data Access Protocol)

The modern, HTTPS-based successor to WHOIS that returns structured JSON registration data.

RDAP is the IETF-standardized replacement for the 40-year-old WHOIS protocol. Instead of free-form text over port 43, RDAP serves structured JSON over HTTPS, which makes it directly consumable by software — and, increasingly, by AI agents that need machine-readable answers about domain registration state.

RDAP supports internationalized domain names, differentiated access levels, and secure transport by default. ICANN has required gTLD registries and registrars to operate RDAP services since 2019, and WHOIS port-43 service for gTLDs was formally sunset in January 2025, making RDAP the authoritative lookup path.

DomainFind.ai uses RDAP as its primary verification method: a 404 from the registry's RDAP endpoint is a strong registry-level signal that a domain is unregistered. Results verified this way carry a confidence score of 0.97 or higher.

Related terms

WHOIS — The legacy port-43 protocol for querying domain registration records, now superseded by RDAP.
Domain Availability — Whether a domain can be registered right now at standard pricing.
Registry vs. Registrar — The registry operates a TLD's database; registrars sell registrations to the public.

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