Country codes: ISO, calling codes and internet domains

Four code systems, four organisations

• ISO 3166-1 is the international standard for country codes, maintained by the ISO 3166 Maintenance Agency. It assigns each country and territory a two-letter (alpha-2), three-letter (alpha-3) and numeric code: 249 in total, of which 196 belong to the countries on this site and 53 to territories such as Greenland (GL) and Puerto Rico (PR), plus Antarctica (AQ).
• Numeric codes are the UN Statistics Division’s M49 codes. They survive a change of name: when Swaziland became Eswatini, 748 stayed 748.
• Calling codes are assigned by the International Telecommunication Union (ITU) under Recommendation E.164 and have nothing to do with ISO: the UK is GB in ISO but +44 for telephones.
• Internet country-code domains are delegated by IANA. They follow the ISO alpha-2 code with one exception, the United Kingdom’s .uk.

Codes change when countries do. Nauru asked the UN in 2026 to use its Nauruan name, Naoero; the UN’s M49 list now shows the new name with the old codes (NR, NRU, 520). AP reported that the three-letter code would become NRO, but no change had been published by 12 November 2026, so the table keeps NRU.

Codes that don’t match the English name

27 of the 196 alpha-2 codes do not start with the first letter of the country’s English name, and 68 alpha-3 codes do not begin with their alpha-2 code (Austria is AT but AUT). There are three main reasons: the code follows the country’s own name, it follows an older name, or it had to be told apart from a similar name.

Codes from the country’s own language

Old names, word order and similar names

The remaining mismatches come from word order (Saint Kitts and Nevis is KN, Saint Lucia LC, Saint Vincent VC, the United Arab Emirates AE) and from English short names that differ from ours (Micronesia is FM for Federated States of Micronesia). The ISO Maintenance Agency does not publish a reason for each code; these are the standard explanations.

Calling codes: zones and shared codes

The first digit of a calling code identifies a world zone. Zone 2 is Africa, zones 3 and 4 Europe, 5 Latin America, 6 Southeast Asia and Oceania, 8 East Asia and 9 the rest of Asia. Zones 1 and 7 are single shared numbering plans. Of the 196 countries, 15 have a one-digit code, 45 two digits and 136 three digits; large countries tend to have the shortest.

Countries on this site by the first digit of their ITU calling code.

• +1 is shared by 13 countries in the North American Numbering Plan, from the United States and Canada to 11 Caribbean states, each with its own area code.
• +7 is shared by Russia and Kazakhstan. In June 2026 the ITU returned +997, once set aside for Kazakhstan, to the spare pool after the two countries agreed to keep sharing zone 7.
• +39 covers Italy and Vatican City; +379 is assigned to the Vatican but reserved for future use.
• +970 is reserved by the ITU for the Palestinian Authority, and +886 is used by Taiwan.
• Territories often share their state’s code (Jersey, Guernsey and the Isle of Man use +44) or have their own (Greenland +299, Hong Kong +852).

Internet domains: why .uk and not .gb

Every country on this site has an active country-code top-level domain in IANA’s root zone, and all but one match the ISO alpha-2 code. The exception is the United Kingdom: .uk was already in use when country domains were tied to ISO codes, and IANA allowed it to continue on condition that .gb is reserved and never used. The .gb domain still exists in the root zone, managed by IANA itself as a reserved name.

Some country domains are better known for other uses than for their country: Tuvalu’s .tv, the British Indian Ocean Territory’s .io and Colombia’s .co are widely sold to businesses worldwide. The .eu domain belongs to the European Union, not a country, and .su, the Soviet Union’s domain, is still active more than three decades after the country dissolved.

Frequently asked questions