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.
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).
[2] The registered country code extensions in 1988 included .ie (Ireland) .it (Italy), .es (Spain) and .pt (Portugal).
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.
"[42] Also unofficially used by Canton of Schaffhausen in Switzerland Internationalised domain names have been proposed for Japan and Libya.
Under RFC 1591 rules, .um is eligible as a ccTLD on request by the relevant governmental agency and local Internet user community.
There are three ccTLDs that have been deleted after the corresponding 2-letter code was withdrawn from ISO 3166-1: cs (for Czechoslovakia), zr (for Zaire) and tp (for East Timor).
The historical country codes dd for the German Democratic Republic and yd for South Yemen were eligible for a ccTLD, but not allocated; see also de and ye.
Finally, after a two-year transition to Serbian rs and Montenegrin me, the .yu domain was phased out in March 2010.
Australia was originally assigned the oz country code, which was later changed to au with the .oz domains moved to .oz.au.
ICANN started to accept applications for IDN ccTLDs in November 2009,[85] and installed the first set into the Domain Names System in May 2010.
The .co domain of Colombia has been cited since 2010 as a potential competitor to generic TLDs for commercial use, because it may be an abbreviation for company.
The domain cm of Cameroon has generated interest due to the possibility that people might miss typing the letter o for sites in the com.