ISO 3166-1 alpha-2 codes are the best known part of ISO 3166-1 and subsequent use as most of the country codes for Internet domain names.
Starting in the mid-1980s, the two-letter codes have been used in domain names on the Internet, where they are used to form country code ccTLDs, with some exceptions e.g. Great Britain, where ICANN did not follow the ISO 3166-1 and used UK instead of GB.
The two-letter ISO 3166-1 codes form the first two letters of the three-letter ISO 4217 standard codes for currencies.
They are also used for International Bank Account Numbers, the ISO 6166 International securities identification numbering (ISIN) system, ISO 7372, ISO 9375, the ISO/IEC 7501-1 machine readable travel documents standard, UN/LOCODE (United Nations Economic Commission for Europe Recommendation 16, for encoding names of ports), and WIPO standard ST.3 (for encoding country which issued a patent or trademark).
Changes to ISO 3166-1 alpha-2 are tracked by ISO 3166-3.
Note that AA, ZZ and the ranges QM-QZ and XA-XZ are reserved for private use.
In addition, OO is designated as an escape code.
If a country code cannot be found in the list then it is probably obsolete, in which case it should be found in the list of obsolete country codes, further below.
The following is intended to be a complete list of current ISO 3166-1 two-letter codes.
Reserved code elements are codes which, while not ISO 3166-1 codes, are in use for some applications in conjunction with the ISO 3166 codes. The ISO 3166 MA therefore reserves them, so that they are not used for new official ISO 3166 codes, thereby creating conflicts between the standard and those applications. The alpha-2 reserved code elements list, as of July 23, 2003, is as follows.
A transitional reservation refers to a code which was formerly present in ISO 3166, but which since has been deleted. It will be maintained as a transitional reservation for at least five years, for the sake of users who still need to refer to the former entity or whose systems have not yet been updated to refer to the new code. The transitionally reserved alpha-2 code elements are:
Uses and applications
ISO 3166-1 Alpha-2 Reserved Code Elements list
The indeterminately reserved alpha-2 code elements are code elements used to identify vehicles under the 1949 and 1968 United Nations Road Traffic Conventions. These codes differ from those used in ISO 3166. The ISO 3166 MA hopes that these codes will eventually be phased out and that ISO 3166-1 codes will be used instead; but in the meantime they are reserved, to avoid conflicts between ISO 3166-1 and the Conventions, and to facilitate any transition from the Convention codes to ISO 3166-1 codes. These codes are as follows:
Notes:
Exceptionally reserved alpha-2 code elements are reserved permanently because they are needed for particular purposes. ISO 3166 MA only authorizes their use for the particular purpose for which they were established. The list is as follows:
In addition, the ISO 3166 MA has undertaken, for the time being, not to use the following alpha-2 codes from WIPO Standard ST.3. However, this undertaking is not classified as an transitional, indeterminate or transitional reservation, since the codes do not refer to countries, dependent areas or other geographic regions or localities:
In addition, WIPO Standard ST.3 also uses EA to code the Eurasian Patent Organization. However, ISO 3166 MA has stated it cannot guarantee to reserve the code EA from use, since it is already used for customs purposes to represent Ceuta and Melilla. ISO 3166 MA proposed in 1995 that EV be used by WIPO for the purpose of representing the Eurasian Patent Organization; however, this request was not honoured by WIPO.