.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
Domain Name System ASCII characters permitted in the DNS prevented the representation of names and words of many languages in their native alphabets or scripts. To make this possible, ICANN approved the Internationalizing Domain Names in Applications (IDNA) system, by which user applications, such as web browsers, map Unicode strings into the valid DNS character set using Punycode. In 2009 ICANN approved the installation of internationalized domain name country code top-level domains ("ccTLD"s). In addition, many registries of the existing top-level domain names ("TLD"s) have adopted the IDNA system. The Domain Name System is maintained by a distributed database system, which uses the