WHOIS (who is) is the aptly named Internet function that allows one to query remote WHOIS databases for domain registration information. By performing a simple WHOIS search you can discover when and by whom a domain was registered, contact information, and more. A WHOIS search can also reveal the name or network mapped to a numerical IP address.

In the case of a privately owned domain, the WHOIS database contains the full name, address, telephone number, and email address of the registered owner of the domain. If the domain is owned by a business, the company name, address, email, and telephone number are listed. There are also fields for a domain administrator, technical administrator, and other contacts. The expiration date of the registration period is also listed.