What is RDAP?
Also known as: Registration Data Access Protocol
RDAP (Registration Data Access Protocol) is a modern RESTful protocol for querying domain name and IP address registration data, replacing the older WHOIS protocol with structured JSON responses and role-based access controls.
RDAP (Registration Data Access Protocol) is a RESTful web service protocol standardized in RFC 7480 through RFC 7484 for accessing registration data about domain names, IP addresses, and autonomous system numbers. It was developed by the IETF WEIRDS working group as a replacement for the WHOIS protocol, which had grown outdated due to its lack of structured data, internationalization support, and access control mechanisms.
RDAP operates over HTTP or HTTPS and returns data in JSON format. Clients send GET requests to RDAP servers using hierarchical URLs that follow a pattern like /domain/example.com or /ip/192.0.2.0/24. The protocol supports query redirection through HTTP 301/302 redirects, allowing registries to delegate queries to registrars automatically. RDAP also implements role-based access controls through HTTP authentication, enabling registries to differentiate between public queries (accessing thin data) and authenticated queries (accessing thick data or sensitive information).
In the broader internet infrastructure stack, RDAP sits alongside DNS and WHOIS as a directory service for registration data. It is gradually being adopted by regional internet registries (RIRs) and domain registries as they phase out WHOIS. The Internet Corporation for Assigned Names and Numbers (ICANN) has mandated RDAP support for all gTLD registries and registrars since 2019. RDAP addresses several WHOIS limitations: it supports internationalized domain names (IDNs) via Unicode, provides standardized error codes, and allows for partial response throttling to prevent abuse.
Key facts
- Standardized in RFC 7480-7484 (2015) by the IETF WEIRDS working group.
- Returns registration data in JSON format over HTTP or HTTPS.
- Supports query redirection via HTTP 301/302 for delegated lookups.
- Implements role-based access controls for public versus authenticated queries.
- ICANN mandated RDAP for all gTLD registries and registrars effective 2019.
How it works in practice
Related terms
References
- RFC 7480: HTTP Usage in the Registration Data Access Protocol (RDAP)
- RFC 7481: Security Services for the Registration Data Access Protocol (RDAP)
- RFC 7482: Registration Data Access Protocol (RDAP) Query Format
- RFC 7483: JSON Responses for the Registration Data Access Protocol (RDAP)
- RFC 7484: Finding the Authoritative Registration Data Access Protocol (RDAP) Service
More in Domains
Auth Code
A unique, per-domain secret code that the losing (current) registrar must provide so the gaining (new) registrar can authorize a domain transfer.
ccTLD
A ccTLD is a two-letter top-level domain assigned to a country or territory based on the ISO 3166-1 alpha-2 code, such as .us for the United States or .jp for Japan.
Domain Lock
A registrar-level status that prevents unauthorized domain transfers, modifications, or deletions until the registrant explicitly removes the lock.
Domain Privacy
An optional service that replaces the domain registrant's personal contact information in WHOIS records with the registrar's proxy details to shield the owner from spam and unwanted disclosure.
EPP
EPP (Extensible Provisioning Protocol) is an XML-based application protocol used by domain name registries and registrars to provision domain names, manage contacts, and transfer registrations.
Grace Period
The grace period is a window after a domain expires during which the registrant can renew at the standard renewal fee, without incurring additional redemption costs.
IDN
An Internationalized Domain Name (IDN) is a domain name that includes characters outside the ASCII set, encoded as Punycode for compatibility with the DNS.
Punycode
Punycode is a method defined in RFC 3492 for converting Unicode strings into ASCII labels, enabling Internationalized Domain Names (IDNs) to be used in the DNS.
Registrant
The registrant is the legal holder of a domain name, listed as the owner in the registry database and responsible for the domain's renewal and administration.
Registrar
A domain registrar is an ICANN-accredited company that sells domain name registrations to individuals and organizations, managing the reservation of domain names within the DNS.