Country Code Top Level Domain Definition

A country code top level domain (ccTLD) is a unique two-letter string (i.e., sequence of characters) that has been assigned to a country or other geographical area in order to identify it in a domain name.

A domain name is a name that uniquely identifies a site (e.g., web site or ftp site) on the Internet or other TCP/IP (transmission control protocol/Internet protocol) network. A top level domain (TLD) is the last part of a domain name; that is, it is the segment, or segments if a ccTLD is used, furthest to the right.

TLDs are classified into two main groups: generic (gTLD) and country code. The former each consist of at least three alphabetic characters and include strings such as .com (commercial), .net (network), .org (organization), .gov (U.S. government), .edu (education) and .mil (U.S. military).

In contrast to the handful of gTLDs, there are more than 240 ccTLDs. Examples include .ac (Ascension Island), .ae (United Arab Emirates), .cl (Chile), .es (Spain), .fr (France), .in (India), .jp (Japan), .ml (Mali), .nz (New Zealand), .pw (Palau), .ru (Russia), .se (Sweden) and zw (Zimbabwe).

Use of the ccTLD is optional when creating a domain name. For example, although the U.S. has a country code (.us), most American Web sites use only a gTLD and omit the ccTLD. When a ccTLD is used, it always follows the gTLD if a gTLD is also used.

Most ccTLDs correspond to the two-letter ISO 3166-1 country codes. ISO 3166-1 is part of the ISO 3166 standard, which was first published in 1974 by the International Organization for Standardization and defines three different codes for each country or other geographic area: a two-letter system, a three-letter system and a three-digit numerical system.

Among the few differences between the ISO 3166-1 country codes and the ccTLDs are that some of the ISO country codes are not used as ccTLDs and that there are some ccTLDs that do not conform to the ISO codes. An example of the latter is .uk (United Kingdom), one of the most frequently used ccTLDs. Another is .eu (European Union), which finally started becoming available in late 2005 after years of discussion.

.eu is also unusual in that it is for a group of countries rather than for a single country.Likewise, Antarctica is a continent that has its own ccTLD (.aq). (Although Australia is also a continent that has its own ccTLD, .au, it is also a country.)

In addition, there are a number of parts of countries and dependent territories that have their own ccTLDs, such as .fo (Faroe Islands), .hk (Hong Kong), .pr (Puerto Rico), .vg (Virgin Islands, British), .vi (Virgin Islands, U.S.), .wf (Wallis and Futuna).

Overall responsibility for the ccTLDs belongs to IANA (Internet Assigned Numbers Authority). However, each country appoints a manager, or managers, for its ccTLD and sets the rules for allocating domain names within it. For example, some countries allow anyone, regardless of their citizenship or location, to acquire a domain in their ccTLD, whereas others allow only residents to acquire a domain in their ccTLD.

A complete list of current ccTLDs is available on IANA's web site at

Created December 9, 2005.
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