RDAP vs WHOIS: What Replaced WHOIS And Why

WHOIS is a protocol from 1982. It runs on TCP port 43, returns free-form text, and was never designed for either machine consumption or modern privacy regulation. The reply format differs between every registry — VeriSign formats .com one way, Nominet formats .uk a different way, and ARIN's IP responses look different again.

For decades that was tolerated because the data was useful and there was nothing better. Two pressures changed that: privacy regulation made the old free-text format problematic, and automation made the lack of structure painful.

RDAP — the Registration Data Access Protocol — is the IETF's successor, standardized in RFCs 7480–7484 and refined since. The important properties:

• HTTPS instead of cleartext TCP 43.
• JSON output with stable, documented keys.
• Standard HTTP status codes (200, 404, 429) for errors.
• Bootstrap registry at IANA tells you which RDAP server to query for any TLD or IP range.
• Authentication hooks so authorized parties (law enforcement, registrars) can request fuller data.

The same query that produces a paragraph of WHOIS text produces a clean JSON object with fields like handle, status, events, and entities.

Before May 2018, WHOIS for most TLDs included the registrant's full name, address, phone number, and email. After GDPR, registries and registrars covering EU registrants — effectively all of them — stopped publishing personal data of natural persons.

Today the public RDAP / WHOIS view typically shows:

• Registrar name and IANA ID.
• Status codes (clientTransferProhibited, etc.).
• Creation, last-updated, and expiration dates.
• Nameservers.
• An abuse contact email at the registrar.

Names and personal contact details for the registrant are usually redacted. To reach the registrant, route through the registrar's disclosure process.

Practical rule of thumb:

• Use RDAP for anything programmatic, anything user-facing, and any new TLD. The JSON output is parseable, the errors are sensible, and it is what newer registries actually publish.
• Use WHOIS when you specifically need a legacy text response (some tools and forensic workflows still expect it) or when querying a registry that only operates port-43 service.

Codynet's domain RDAP lookup and IP RDAP lookup both go directly against the right RDAP server using IANA bootstrap data, so you never have to remember which TLD lives where.

A trimmed RDAP response for a domain looks like:

{
  "objectClassName": "domain",
  "ldhName": "example.com",
  "status": ["client transfer prohibited"],
  "events": [
    { "eventAction": "registration",  "eventDate": "1995-08-14T04:00:00Z" },
    { "eventAction": "expiration",    "eventDate": "2027-08-13T04:00:00Z" },
    { "eventAction": "last changed",  "eventDate": "2025-08-14T07:00:00Z" }
  ],
  "nameservers": [
    { "ldhName": "a.iana-servers.net" },
    { "ldhName": "b.iana-servers.net" }
  ],
  "entities": [
    { "roles": ["registrar"], "vcardArray": [...] }
  ]
}

Every key is stable across registries. Compare that to the equivalent WHOIS response, which would be roughly 40 lines of free-form text with field names that vary by registry.