.co (second-level domain) .co (second-level domain) In a number of countries, .co is used as a second-level domain to mean "commercial" and domain registrants register second-level domains of the form .co.xx, where xx is the country code top level domain (e.g., .co.uk in the U.K. and .co.jp in Japan). Some of the countries using .co as a second-level domain include: Barbados (.bb), Cook Islands (.ck), Costa Rica (.cr), India (.in), Indonesia (.id), Israel (.il), Japan (.jp), New Zealand (.nz), South Africa (.za), South Korea (.kr), Thailand (.th) and the United Kingdom (.uk). .co is also a country top-level domain corresponding to Colombia. Its
Country code top-level domain Country code top-level domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all two-letter top-level domains are ccTLDs. In 2018, the Internet Assigned Numbers Authority (IANA) began implementing internationalized country code top-level domains, consisting of language-native characters when displayed in an end-user application. Creation and delegation of ccTLDs is described in RFC 1591, corresponding to ISO 3166-1 alpha-2 country codes. As of 2015, IANA distinguishes the following groups of top-level domains: