February 2017


"Whois" is a tool for querying information bases (called registries) regarding domain names and IP addresses. The data contained in these registries bears no guarantee, but may generally be used to find out who owns a domain name or a machine, particularly if a dispute arises.

Whois has two main purposes:

  • Retrieving information on the owner of a domain name (for administrative, technical, and possibly billing purposes) and the servers associated with the domain.
  • Retrieving information on whom a given range of IP addresses belongs to.

Command-line Whois tools are available for certain operating systems, including Unix (such as Linux or MacOS X), in which the command syntax is as follows:

whois domain_name_or_ip_address
There are usually a large number of settings for this command, depending on the operating system. To learn what they are, simply enter:
whois --help

There are also online Whois lookup services for nearly all domain name extensions, most of which are accessible at http://whois.nic.extension, where extension stands for the final part of the domain name. A simple search for "whois" in a search engine also gives the addresses of websites that offer such services.

IP addresses

Administrative information regarding IP addresses are archived by the following organizations (source: IANA):

  • RIPE NCC (Réseaux IP européens, meaning ""European IP Networks", whois.ripe.net) for Europe;
  • APNIC (Asia Pacific Network Information Centre, whois.apnic.net) for Asia and the Pacific;
  • ARIN (American Registry for Internet Numbers, whois.arin.net) for North America and Sub-Saharan Africa;
  • LACNIC (Regional Latin-American and Caribbean IP Address Registry, whois.lacnic.net) for Latin America and the Caribbean;
  • INTERNIC (whois.internic.net) for other parts of the world.
The first byte in the IP address indicates which region the address belongs to:


This document, titled "Whois," is available under the Creative Commons license. Any copy, reuse, or modification of the content should be sufficiently credited to CCM (ccm.net).