About .arpa domains

About .arpa domains

.ARPA is a top-level domain delegated in the IANA root zone. See the official IANA delegation record for manager and technical contacts.

The domain name arpa is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. It is used predominantly for the management of technical network infrastructure. Prominent among such functions are the subdomains in-addr.arpa and ip6.arpa, which provide namespaces for reverse DNS lookup of IPv4 and IPv6 addresses, respectively. The name originally was the acronym for the Advanced Research Projects Agency (ARPA), the funding organization in the United States that developed the ARPANET, the precursor of the Internet. It was the first domain defined for the network in preparation for a hierarchical naming system for the delegation of authority, autonomy, and responsibility. It was originally intended only to serve in a temporary function for facilitating the systematic naming of the ARPANET computers. However, it became practically difficult to remove the domain after infrastructural uses had been sanctioned. As a result, the name was redefined as the backronym Address and Routing Parameter Area. Domain-name registrations in arpa are not possible, and new subdomains are infrequently added by the Internet Engineering Task Force.

Who can register .arpa domains?

Eligibility is defined by the registry operator and its registrars. Most gTLDs are open to anyone worldwide. Many ccTLDs are also open globally; some require local presence, citizenship, or trademark rights. Always confirm current policy with the registry or your registrar.

Registration restrictions

Character rules below follow common ICANN LDH conventions. Individual registries and registrars may impose extra eligibility, length, or residency rules.

Length

2 – 63 characters (label before .arpa)

Can use

Letters (a–z), numbers (0–9), and hyphens (not first/last or consecutive in restricted cases)

Cannot use

Special characters (e.g. & # @) in standard LDH labels

IDNs

Varies by registry — check IDN support with the registry or your registrar

Features

Operational features (privacy, parking, protection) are registrar-level, not defined by the IANA root zone record.

Registry information

Sponsor / manager

Internet Architecture Board (IAB)

Registration services

https://www.iana.org/domains/arpa

WHOIS server

whois.iana.org

Root zone registration

1985-01-01

Record last updated

2023-11-27