In a number of countries, .co (an abbreviation of commercial) is used as a second-level domain in the Domain Name System used to route internet traffic. 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).
Countries using .co as a second-level domain include: Angola ( .ao), 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), United Kingdom ( .uk) and Venezuela ( .ve).
.co is also a country top-level domain corresponding to Colombia. Its current manager, Neustar, markets it globally as an alternative to .com. [1]