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. While gTLDs have to obey international regulations, ccTLDs are subjected to requirements that are determined by each country's domain name regulation corporation. With over 150 million domain name registrations as of 2022, ccTLDs make up about 40% of the total domain name industry.

Country code extension applications began in 1985. The registered country code extensions in that year included .us (United States), .uk (United Kingdom) and .il (Israel). The registered country code extensions in 1986 included .au (Australia), .de (Germany), .fi (Finland), .fr (France), .is (Iceland), .jp (Japan), .kr (South Korea), .nl (Netherlands) and .se (Sweden). The registered country code extensions in 1987 included .nz (New Zealand), .ch (Switzerland) and .ca (Canada). The registered country code extensions in 1988 included .ie (Ireland) .it (Italy), .es (Spain) and .pt (Portugal). The registered country code extensions in 1989 included .in (India) and .yu (Yugoslavia). In the 1990s, .cn (People's Republic of China) and .ru (Russian Federation) were first registered.

There are 308 delegated ccTLDs. The .cn, .tk, .de, .uk, .nl and .ru ccTLDs contain the highest number of domains. The top ten ccTLDs account for more than five-eighths of registered ccTLD domains. There were about 153 million ccTLD domains registered at the end of March 2022.

IANA is responsible for determining an appropriate trustee for each ccTLD. Administration and control are then delegated to that trustee, which is responsible for the policies and operation of the domain. The delegation can be determined from IANA's list of ccTLDs. Individual ccTLDs may have varying requirements and fees for registering subdomains. There may be a local-presence requirement (for instance, citizenship or other connection to the ccTLD), as, for example, the American (us), Japanese (jp), Canadian (ca), French (fr) and German (de) domains, or registration may be open.

The first registered ccTLD was .us, which was registered in 1985. Later ccTLDs registered in that year included .uk and .il. Then, .au, .de, .fi, .fr, .is, .jp, .kr, .nl and .se were also registered in 1986. In 1987, .nz, .ch, .my and .ca were registered. Later on, in 1988, .ie, .it, .es and .pt were also registered.

As of 20 May 2017, there were 255 country-code top-level domains, purely in the Latin alphabet, using two-character codes. The number was 316 as of June 2020^[update], with the addition of internationalized domains.

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