.uk is the Internet country code top-level domain (ccTLD) for the United Kingdom of Great Britain and Northern Ireland. As of March 2012, it is the fourth most popular top-level domain worldwide (after .com, .de and .net), with over 10 million registrations.
New registrations directly under .uk are generally not permitted. Instead, registrations are made under a selection of second-level domains.
It is prohibited to register a domain name directly under the ccTLD .uk. No restrictions for .co.uk, .me.uk, and .org.uk; other subdomains have differing restrictions