| Introduced | 1985 |
|---|---|
| TLD type | Country code top-level domain |
| Status | Unused |
| Registry | JANET(UK) |
| Sponsor | JANET(UK) |
| Intended use | Entities connected with United Kingdom |
| Actual use | Fallen into disuse in favour of .uk |
| Registration restrictions | No registrations presently being taken |
| Structure | Government sites formerly found under hmg.gb |
| Dispute policies | None |
| Website | None |
.gb is a reserved Internet country code top-level domain (ccTLD) for the United Kingdom. Introduced at the same time as the UK's other top-level domain (.uk), it was never widely used. It is no longer possible to register under this domain.
The rule in the Domain Name System is that a top-level domain for a country is derived from the corresponding two-letter code in the ISO 3166-1 list. Accordingly the correct code for the United Kingdom of Great Britain and Northern Ireland is GB, and the .gb top-level domain was therefore delegated.
The pre-existing JANET Name Registration Scheme had used "UK" as a country code, so the UK also applied to Jon Postel of IANA for the .uk TLD. This was granted, and all UK domain names are now issued as .uk, rather than .gb.
.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.[1]
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 open to new subdomain registrations.
One .gb subdomain still exists in the DNS (as of 2010): dra.hmg.gb[2], belonging to Her Majesty's Government's former Defence Research Agency, and has three known hostnames remaining: hermes.dra.hmg.gb,[3] delos.dra.hmg.gb[4] and dfhnet.dra.hmg.gb.[5]