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WHOIS

WHOIS is an older set of rules for requesting information and a name commonly used for services that look up registration information about domain names. A user enters a domain in a WHOIS lookup tool; the tool sends a query to a WHOIS server and displays the text response. The name is commonly pronounced “who is”; it is not an acronym.

What might a WHOIS result contain?

Depending on the server and the domain ending, a result may identify the registrar, show registration or expiration dates, list nameservers, or include registrant contact fields. The format and available fields have varied between services. Contact details may be hidden or replaced with a privacy contact, so a WHOIS result may not identify the person behind a domain.

For example, Sam searches for sam-bakery.example and sees the registrar and nameservers, while the contact section says “redacted for privacy.” The result still helps Sam identify which registrar manages the registration. It does not reveal the registrant's email address, and it does not mean the domain is unregistered.

How did WHOIS work?

The classic WHOIS protocol sends a text query to a server over a network connection using TCP port 43, and the server returns text. A browser-based lookup site can perform this request on a person's behalf. WHOIS does not define one consistent structure for every field in every response, so different servers and lookup tools may format results differently.

The protocol also lacks built-in support for strong security and access control, and it has no standard way to declare how its text characters are represented as computer data. These are properties of the WHOIS protocol described in the IETF specification; individual websites may add features around their own lookup service, but those additions do not change the protocol itself.

Is WHOIS still used?

For generic top-level domain (gTLD) registration data, ICANN made RDAP the definitive source starting 28 January 2025, and ICANN-accredited registrars and gTLD registries were no longer generally required to provide WHOIS services from that date, with exceptions identified by ICANN. WHOIS may still be available in some systems and for some domain endings, so its availability depends on the registry and applicable rules.

RDAP returns structured data that software can interpret more consistently and was designed to address several limitations of WHOIS. Both systems are ways to query registration data. Neither one checks whether the associated website, hosting, or email is working. For the information itself and why some fields may be missing, see domain registration data.

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