.co.uk
| Introduced | 1985 |
|---|---|
| TLD type | Country code top-level domain |
| Status | Active |
| Registry | Nominet UK |
| Sponsor | Nominet UK |
| Intended use | Entities connected with the  United Kingdom
|
| Actual use | Entities connected to the United Kingdom |
| Registered domains | 10,586,358 (10,298,553 third level and 287,805 second level) (31 March 2015) |
| Registration restrictions | None |
| Structure | [name].uk [name].[generic domain].uk |
| Dispute policies | DRS Policy |
| Website | nominet.uk |
| DNSSEC | Yes |
.uk is the Internet country code top-level domain (ccTLD) for the United Kingdom of Great Britain and Northern Ireland. As of February 2016[update], it is the fifth most popular top-level domain worldwide (after .com, .cn, .de and .net), with over 10 million registrations.
In October 1984, RFC 920 set out the creation of ccTLDs generally using country codes derived from the corresponding two-letter code in the ISO 3166-1 list. GB is the UK's ISO 3166 country code. However, the .uk domain had been created separately a few months before the compilation of the ISO-derived list. Consequently, .gb was never widely used and it is no longer possible to register under that domain.
New registrations directly under .uk have been accepted by Nominet since 10 June 2014 08:00 BST, however there is a reservation period for existing customers who already have a .co.uk, .org.uk, .me.uk, .net.uk, .ltd.uk or .plc.uk domain to claim the corresponding .uk domain, which runs until 07:59 BST on 10 June 2019.
.uk has used OpenDNSSEC since March 2010.
As with other ccTLDs in the early days it was originally delegated to an individual by Jon Postel. In time, it passed to Willie Black at the UK Education and Research Networking Association (UKERNA). Originally, domain requests were emailed, manually screened by and then forwarded to the UK Naming Committee before being processed by UKERNA. Membership of this committee was restricted to a group of high-end ISPs who were part of a formal peering arrangement.
The Naming Committee was organised as a mailing list to which all proposed names were circulated. The members would consider the proposals under a ruleset that insisted that all domain names should be very close if not identical to a registered business name of the registrant. Members of the Naming Committee could object to any name, and if at least a small number of objections were received, the name was refused.
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