What is Whois?

As we outlined in the Anatomy of a domain name section, the domain name can be split into logical sections, such as Registrant, Admin Contact, Tech Contacts, and Nameservers. All of these sections are described and enumerated in records called Whois records and Whois servers serve those records. While in the early days, Whois records were merely informational repositories of points-of-contact for domain names, as the internet became more integral to everyday living and business, these records became of the utmost importance. They have legal bearing now; they are used to decide ownership disputes and liability issues. There exist forensic Whois record auditors who trace domain ownership using these records to assess whether a given domain may be stolen.

The Whois servers are internet hosts that listen for Whois requests (typically on port 43), and they respond to queries about given domain names with the associated Whois records for them. While traditionally there have been best practices for the format of Whois records, every registry and registrar has their own output format.