What Is RDAP?

RDAP (Registration Data Access Protocol) is the modern, standards-based replacement for the legacy WHOIS protocol. It provides structured registration data for domains, IP addresses, and ASNs over HTTPS, returning machine-readable JSON responses instead of the unstructured plain-text output that WHOIS delivers.

RDAP vs WHOIS

WHOIS has been in use since the 1980s and returns plain-text responses with inconsistent formatting across different registries. RDAP was designed by the IETF (Internet Engineering Task Force) to address these limitations. Key advantages of RDAP include standardized JSON output, HTTPS transport with authentication support, internationalized content support, and better access control mechanisms.

What RDAP can look up

• Domains -- registration dates, nameservers, registrar information, and domain status codes
• IP addresses -- network allocation, owning organization, abuse contacts, and netblock ranges
• ASNs -- autonomous system registration data, operator identity, and contact information

How RDAP bootstrap discovery works

RDAP uses a bootstrap system maintained by IANA to determine which server is authoritative for a given query. When you look up an IP address, the system checks the IANA bootstrap files to find the correct Regional Internet Registry (RIR) RDAP endpoint. For domains, it identifies the correct registry or registrar RDAP server based on the top-level domain.

Limitations of RDAP

RDAP shows publicly available registration data only. Many domain registrations use privacy services that replace the registrant contact information with proxy details. Additionally, not all registries have fully implemented RDAP, though adoption has grown significantly since ICANN began requiring it for domain registrars.