WHOIS is a long-standing query-and-response protocol used to look up registration information about internet resources, most commonly domain names. A WHOIS query returns records held by registrars and registries, including who registered a domain, when it was created, when it expires, and which name servers it uses.
The data has many practical uses. Marketers and sales teams check domain creation dates to gauge how established a business is, security researchers investigate suspicious domains, and buyers evaluate whether a domain is available or when it expires. The domain age revealed by WHOIS is a common trust signal in lead qualification.
Privacy regulations, especially GDPR, have significantly reduced the personal detail WHOIS exposes. Many registrars now redact registrant names and contact information behind privacy services, so modern WHOIS responses often show registrar and date fields while masking the individual behind the registration.
WHOIS is gradually being succeeded by RDAP, a newer protocol that returns the same kind of data in a structured, standardized JSON format with better support for access control and internationalization. For now, both coexist, and WHOIS remains the familiar way to answer basic questions about who holds a domain and how old it is.