ISO 3166

ISO 3166 is an international standard issued by the International Organization for Standardization (ISO). It defines short codes for countries, territories administered by other countries, and subdivisions such as regions and provinces. The purpose is to enable computer systems, commerce, and official data to use brief, unambiguous symbols instead of full names that would be written differently in each language.

ISO 3166 codes are used in many contexts: country domain names on the internet, passports and travel documents, bank accounts and money transfers, and data collection by international organizations. The list is constantly updated: when a country changes its name or new borders are created, ISO revises it.

Parts of the standard

The standard is divided into three main parts. The first part (ISO 3166-1) provides codes for countries and territories. The second part (ISO 3166-2) defines the subdivisions of each country, such as regions or major districts. The third part (ISO 3166-3) preserves the former codes of countries that changed their names or split up, so that historical data can be understood.

Types of country codes

ISO 3166-1 has three forms. Alpha-2 consists of two letters and is the most common—for example, it is used for country-level internet domain names. Alpha-3 consists of three letters and is usually closer to the country name, making it easier for people to recognize. Numeric consists of three digits, useful for systems that cannot use Latin characters or need language-neutral data.

Administration

A dedicated committee working under ISO decides on codes. The committee relies on official information from international organizations and the countries themselves. Requests for new codes usually relate to political changes or when a country adopts a new name. Once a code is assigned, a period elapses before it can be reused, to prevent confusion with earlier data.