WHOIS
WHOIS (pronounced "who is") is an Internet service used to look up information about a domain name. While the term is capitalized, "WHOIS" is not an acronym. Instead, it is short for the question, "Who is responsible for this domain name?"
Domain names are registered through companies called registrars. Examples include GoDaddy, Tucows, Namecheap, and MarkMonitor. These companies have been approved and accredited by ICANN to register new domain names. Whenever an individual or organization registers a new domain name, the registrar is required to make the registration information publicly available. This information can be looked up online using the WHOIS service.
Since there is no central database of domain registration information, WHOIS search engines look up data across multiple registrars. Many registrars provide their own WHOIS lookup service, though several third party WHOIS websites also exist. ICANN provides its own WHOIS lookup service as well (see photo).
What is a WHOIS record?
WHOIS records vary between registrars, but they all contain mandatory information. This includes the name of the registrar, created date, updated date, and expiration date of the domain name. The name servers are also listed. Three contacts are included — the registrant, admin, and technical contacts. This information, provided during registration, includes a name, organization (if applicable), address, phone number, and email address. In many cases, the information is duplicated across all three contacts, though each one may have different information.
NOTE: The contact information in a WHOIS record can be made private using a "private registration" service offered by some registrars. This service, which may be available for an additional fee, masks the registrant's contact information with non-personally identifiable information. A domain registered with domain privacy will still show up in a WHOIS search, but the organization may appear as "Whois Privacy Services" and the email address "abcd1234@whoisprivacyservices.com".
Definition from The Tech Terms Dictionary