countrycodes

Country codes are condensed identifiers used to represent nations and territories across databases, maps, telecommunications, and the internet. They enable concise reference and reduce ambiguity in international data exchange. The most widely adopted system is ISO 3166, which provides multiple code types: alpha-2 (two-letter), alpha-3 (three-letter), and numeric codes. Other notable systems include the ITU-T E.164 country calling codes for telephone dialing, the UN M.49 geographic region numbers, and the ISO 3166-2 subdivision codes used for provinces and states. In international sports, the IOC maintains separate country codes that may differ from ISO codes. The Internet uses two-letter country code top-level domains (ccTLDs) that are generally aligned with ISO 3166-1 alpha-2 codes.

ISO 3166-1 alpha-2 codes are the most common: examples include US for the United States, GB for the United Kingdom, and FR for France. Alpha-3 codes provide a longer form, such as USA, GBR, FRA, while numeric codes offer a purely numeric reference (e.g., 840 for the United States, 826 for the United Kingdom). The European Union is represented by the code EU, which is reserved for the union rather than a single country.

The ISO 3166 Maintenance Agency is responsible for publishing and updating these lists. Updates occur as geopolitical changes arise, such as the creation of new states or boundary adjustments. Users should consult the official ISO listings or IANA for the most current codes when designing systems that rely on standardized country identifiers. Caution is advised when relying on a single coding system, as different contexts (phones, domains, data records, or sporting events) may use different but related schemes.