.co is the country code top-level domain name (ccTLD) for Colombia. A government supported entity was created between Arcelandia S.A. and Neustar, .CO Internet SAS, which manages .co as an open ccTLD. Domain name registration is open to all entities worldwide, and it is marketed as a great alternative to the .com domain space.
.co ranks #21 among all domain extensions, and #13 among all country-code extensions (ccTLDs). Currently, there are 2.1M registered .co domain names. Neustar is the current registry of .co extension.