What is RDAP?

Understanding Registration Data Access Protocol

What is RDAP?

RDAP (Registration Data Access Protocol) is a modern internet protocol designed to replace the 40-year-old WHOIS protocol for querying registration data of internet resources like domain names, IP addresses, and Autonomous System Numbers (ASNs). Developed by the Internet Engineering Task Force (IETF) and standardized in RFC 7483, RDAP provides structured, machine-readable data in JSON format.

Unlike WHOIS which returns unstructured plain text that varies between registrars, RDAP delivers consistent, standardized responses that applications can easily parse and process. This makes RDAP essential for developers building domain monitoring tools, cybersecurity applications, and compliance systems.

RDAP vs WHOIS: Key Advantages

Structured JSON Data

Standardized JSON format eliminates parsing issues, enables reliable automation and integration with modern APIs.

Enhanced Security & GDPR

HTTPS encryption by default with tiered access control for GDPR compliance and privacy protection.

Internationalization

Native support for non-ASCII characters and IDNs in multiple languages including Chinese, Arabic, and Cyrillic.

RESTful API

Predictable URL patterns like /domain/example.com make it intuitive for developers.

Authentication Support

OAuth 2.0 support with built-in rate limiting for fair access and abuse prevention.

Bootstrap Discovery

Automatic discovery of correct RDAP server eliminates need for registry endpoints knowledge.

How Does RDAP Work?

RDAP operates as a RESTful web service over HTTPS. When you query a domain, IP address, or ASN, the RDAP client first consults the IANA bootstrap service to determine the authoritative RDAP server. The query is then forwarded to the appropriate registry or registrar's RDAP endpoint.

RDAP returns structured JSON data containing:

Object class information

Registration details & dates

Status codes & lock states

Contact data (privacy-compliant)

Nameserver information

DNSSEC details

Common RDAP Use Cases

🔍 Domain Intelligence

Track expiration dates, monitor ownership changes, detect suspicious registrations, and manage domain portfolios.

🛡️ Cybersecurity

Investigate malicious domains, trace attack infrastructure, and build automated threat detection systems.

⚖️ Compliance & Legal

Verify ownership for legal proceedings, ensure trademark compliance, and maintain audit trails.

🌐 Network Operations

Query IP allocations, research ASN information, troubleshoot routing issues, and maintain network docs.

RDAP Implementation Status

RDAP is now mandatory for all ICANN-accredited registrars and registries:

gTLDsAll generic top-level domains (.com, .org, .net)

ccTLDsMany country codes (.uk, .ca, .au)

RIRsARIN, RIPE NCC, APNIC, LACNIC, AFRINIC

RegistrarsGoDaddy, Namecheap, Cloudflare, and more

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Frequently Asked Questions

Is RDAP replacing WHOIS completely?

Yes, RDAP is the designated successor to WHOIS. While WHOIS remains for backward compatibility, RDAP is now the primary protocol.

Is RDAP free to use?

Yes, basic RDAP queries are free. Some registries may require authentication for enhanced data or high-volume queries.

How is RDAP more privacy-compliant?

RDAP supports tiered access control, redacting personal information for unauthenticated queries while ensuring GDPR compliance.

Can I query expired domains?

Yes, RDAP can return information about expired domains, including expiration dates and redemption status.