The ISO 3166-1 standard
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Frequently asked questions
What is the ISO 3166-1 standard?
ISO 3166-1 is an international standard published by ISO that assigns unique codes to countries and territories worldwide. It comes in three variants: alpha-2 (2 letters: GB, DE, US…), alpha-3 (3 letters: GBR, DEU, USA…) and numeric (3 digits). It is maintained by the ISO 3166 Maintenance Agency and updated regularly to reflect geopolitical changes.
What are country ISO alpha-2 codes used for?
Alpha-2 codes are the most widely used. They are used for national domain name extensions (ccTLDs: .uk, .de, .us…), in web forms for country dropdown menus, in international shipping labels and barcodes, on European licence plates, and in geographic APIs and databases.
What is the difference between ISO alpha-2 and alpha-3?
Alpha-2 uses 2 letters (e.g. GB for United Kingdom) and is the most common format for everyday use (internet domains, forms). Alpha-3 uses 3 letters (e.g. GBR) and is preferred in contexts where ambiguity must be avoided or in systems that cannot rely on immediate recognition of the 2-letter code, such as biometric passports (ICAO) or UN statistical data.
Do ISO country codes change over time?
Yes, rarely but regularly. Changes occur with the creation of a new state (East Timor 2002, Kosovo 2008, South Sudan 2011), a union (German reunification), a dissolution (USSR, Yugoslavia, Czechoslovakia) or a simple change of official name (North Macedonia 2019, Eswatini 2018). The ISO 3166/MA manages these updates.