Whois service is primarily used to identify and search for a specific domain name. Whois also supports searching IP addresses and propriety intranet systems. For a registered domain lookup, Whois provides administrative information such as registrar and contact information for the individual or organization that controls the domain. Earlier versions of Whois provided services to deliver search results based on the last names of individuals, keyword-based search and searching for domains based on administrator name. These services were discontinued as a result of unethical use.

Whois has been criticized for promoting a lack of domain privacy. However, some registrars offer private registrations, in which the registrar's information is displayed rather than the individual or company who registered the domain.