What is RDAP and Why Did It Replace WHOIS?

The Registration Data Access Protocol (RDAP) is a modern replacement for the long-standing WHOIS protocol, which has served as the primary method for accessing domain and IP registration information for decades. But why did the industry feel the need for a change? Let's explore the history of WHOIS, its limitations, and how RDAP evolved as a more secure, standardized, and machine-readable alternative.

The History of WHOIS and Its Challenges

WHOIS was first introduced in the early 1980s as part of the ARPANET directory service, long before the internet became commercialized. Over time, WHOIS became the de facto protocol for querying registration information of domain names, IP addresses, and autonomous systems.

Despite its widespread use, WHOIS has faced several major issues:

• Unstructured Data: WHOIS responses are plain text and vary greatly depending on the registrar. There's no consistent schema, which makes parsing and automation difficult.
• Lack of Security: WHOIS queries are usually transmitted over unencrypted connections (plain TCP on port 43), making them vulnerable to interception.
• No Standard Error Handling: Error messages are inconsistent, making it hard for automated systems to interpret responses.
• Privacy Concerns: WHOIS often exposes personal information of domain registrants, creating legal and ethical concerns, especially under regulations like GDPR.

Why RDAP Is the Next Evolution

RDAP was developed by the IETF as a more modern alternative to WHOIS. It addresses nearly all of WHOIS’s shortcomings and offers a much more developer- and privacy-friendly approach.

• Structured Data: RDAP responses are returned in JSON format, which is easy to parse and integrate into applications.
• Secure Transport: RDAP uses HTTPS by default, protecting both the request and response from interception or tampering.
• Standardized Protocol: RDAP uses RESTful API principles, making it easy to work with using modern tools and libraries.
• Internationalization Support: RDAP supports Unicode, making it easier to handle globalized domain names and contact data.
• Rate Limiting & Error Codes: RDAP includes standardized error handling and rate-limiting headers, which are essential for large-scale and commercial usage.

Who Supports RDAP?

RDAP is not just a theoretical upgrade — it’s already supported and enforced by key players in the domain ecosystem.

Organization	Role	Support
ICANN	Internet governance body	Mandated RDAP implementation for all gTLD registrars and registries
RIPE NCC	Regional Internet Registry for Europe	Provides RDAP services for IP and AS numbers
Registrars	Entities selling domains	Gradually replacing WHOIS with RDAP-based query endpoints
Registries	Top-level domain operators	Required to publish RDAP server information

RDAP in Action

Unlike WHOIS, which usually returns human-readable text, RDAP returns structured JSON responses. Here's a quick comparison:

WHOIS Response:

Domain Name: EXAMPLE.COM
Registrar: EXAMPLE REGISTRAR INC.
Creation Date: 2020-01-01T12:00:00Z
Registrant Name: John Doe
Registrant Email: [email protected]

RDAP Response:

{
  "objectClassName": "domain",
  "handle": "EXAMPLE.COM",
  "entities": [
    {
      "vcardArray": [
        "vcard",
        [
          ["fn", {}, "text", "John Doe"],
          ["email", {}, "text", "[email protected]"]
        ]
      ]
    }
  ],
  "events": [
    {
      "eventAction": "registration",
      "eventDate": "2020-01-01T12:00:00Z"
    }
  ],
  "links": [
    {
      "href": "https://rdap.example.com/domain/EXAMPLE.COM",
      "rel": "self",
      "type": "application/rdap+json"
    }
  ]
}

Conclusion

RDAP represents a necessary evolution in the way we access internet registration data. It addresses the outdated architecture of WHOIS by offering a secure, standardized, and machine-readable protocol. With support from major internet governance organizations and registrars, RDAP is already well on its way to becoming the default method for querying domain and IP registration data across the internet.

As internet privacy and automation become increasingly important, RDAP provides a strong foundation for the future of domain data access — and it’s here to stay.