Introduced24 July 1985
TLD typeCountry code top-level domain
StatusUnused (reserved)
RegistryJANET (Jisc)
Intended useEntities connected with Great Britain (the United Kingdom)
Actual useFallen into disuse in favour of .uk
Registration restrictionsNo registrations presently being taken
StructureGovernment sites formerly found under hmg.gb

.gb is a reserved Internet country code top-level domain (ccTLD) for the United Kingdom, derived from Great Britain.

The domain was introduced with RFC 920[1] in October 1984 that set out the creation of ccTLD generally using country codes derived from the corresponding two-letter code in the ISO 3166-1 list. However, the .uk domain had been created separately a few months before the compilation of this list.[2] Consequently, .gb was never widely used. It is no longer possible to register under this domain.

.gb was used for a number of years, mainly by British government organisations and commercial e-mail services using X.400-based e-mail infrastructure. This simplified translating between DNS domains and X.400 addresses, which used "GB" as a country code.[3]

With the demise of X.400 e-mail and IANA's general aim of one TLD per country, use of .gb declined; the domain remains in existence, but it is not currently open to new domain registrations.

As of 2021, dra.hmg.gb still exists, with at least three subdomains resolving through DNS (although none serve a website): hermes.dra.hmg.gb, delos.dra.hmg.gb, and dfhnet.dra.hmg.gb.[4][5][6] The domain was originally owned by the Defence Research Agency,[7] which became the Defence Evaluation and Research Agency in 1995 and was split into QinetiQ and the Defence Science and Technology Laboratory in 2001; the website became defunct some time thereafter.[8]

As of November 2022, Central Digital and Data Office's (see Cabinet Office) intention is to inform ICANN early in 2023 that the UK wishes to retire .gb.[9]


  1. ^ J. Postel and J. Reynolds (October 1984), Request for Comments: 920, Network Working Group
  2. ^ Milton Mueller (2002), Ruling the Root: Internet Governance and the Taming of Cyberspace, Cambridge, Massachusetts: MIT Press, p. 79, ISBN 9780262632980
  3. ^ Crepin-Leblond, Olivier M. J. (2003). "International E-mail Accessibility". Archived from the original on 21 May 2008. Retrieved 23 June 2008.
  4. ^ "DNS lookup for hermes.dra.hmg.gb". Retrieved 7 March 2016 – via Google Apps Toolbox.
  5. ^ "DNS lookup for delos.dra.hmg.gb". Retrieved 7 March 2016 – via Google Apps Toolbox.
  6. ^ "DNS lookup for dfhnet.dra.hmg.gb". Retrieved 7 March 2016 – via Google Apps Toolbox.
  7. ^ Gollman, Dieter, ed. (November 1994). "A Consideration of the Modes of Operation for Secure Systems". Computer Security – ESORICS 94. Brighton: Springer-Verlag. p. 335. ISBN 978-3-540-58618-0.
  8. ^ "DERA". DERA. Archived from the original on 17 May 2001. Retrieved 26 November 2006.
  9. ^ Eden, Terence (15 November 2022). "Is it time to retire the .gb top level domain?". Central Digital and Data Office Blog. UK Government. Retrieved 15 November 2022.