They are reserved by the Internet Assigned Numbers Authority (IANA) at the direction of the Internet Engineering Task Force (IETF) as special-use domain names for documentation purposes.

The Internet Corporation for Assigned Names and Numbers (ICANN) operates websites for these domains with content that reflects their purpose.

The domains may be used in documentation without prior consultation with IANA or ICANN.

In practice, these domain names are also installed in the Domain Name System with the Internet Protocol (IP) addresses for Internet Protocol version 4 (IPv4) and IPv6 of a web server managed by ICANN.

The zone files of each domain also define one subdomain name.