Country codes explained

The three ISO 3166 codes

ISO 3166-1 gives every country three codes for the same thing: a two-letter alpha-2 code, a three-letter alpha-3 code and a three-digit numeric code. Alpha-2 is the one that spread furthest, because it is short and was adopted early by the internet and by shipping and banking systems. Alpha-3 reads more naturally (DEU rather than DE) and turns up on passports and in sport. The numeric code exists for systems that avoid Latin letters altogether.

The alpha-2 table is the one worth keeping to hand, because it is the key that other datasets share. Our airport records carry it, and so does the country index on flagdex.net, which lists all 250 ISO 3166 entries with their alpha-3 and numeric codes, capitals and calling codes; its capitals index is the quickest way to check a code against a capital city.

Where the same two letters show up

Domain names. Country-code top-level domains are the ISO alpha-2 code in lowercase: .de, .nl, .jp, .fr. IANA hands a ccTLD to whoever ISO lists, which is why new countries get a domain almost automatically and why a few historic codes (.su for the Soviet Union) outlive the country.

Currencies. ISO 4217 currency codes are the alpha-2 code plus one letter, usually the initial of the currency: US + D for the dollar, GB + P for the pound, JP + Y for the yen, CH + F for the Swiss franc. Supranational currencies start with X or take a code of their own, so the euro is EUR.

Vehicle registration and sport. Oval country stickers and Olympic scoreboards mostly use alpha-3 style codes, but not always the ISO ones: the Olympic committee keeps its own list (GER for Germany, where ISO says DEU).

Telephone codes do not follow. Calling codes come from the ITU E.164 numbering plan and were assigned by region in the 1960s: +1 for North America, +44 for the United Kingdom, +49 for Germany, +81 for Japan. There is no way to derive a calling code from an ISO code or the other way round.

Aviation goes its own way

IATA airport codes carry no country signal at all. LHR, AMS and JFK are three letters chosen for the airport, and nothing in them says United Kingdom, Netherlands or United States. Our guide to IATA codes explains how they are assigned.

ICAO codes do encode geography, but with their own prefix system rather than ISO 3166. The first letter is a region and the second usually a country: E is northern Europe, so EG is the United Kingdom, ED Germany and EH the Netherlands. The contiguous United States is a single letter, K, which is why KJFK has three letters left for the airport itself. The full prefix map is in ICAO code prefixes.

Underneath the two code systems, the airport dataset still keys every record by ISO alpha-2. That is what makes the country hubs on this site possible: pick a code, get every airport in it.

After the code: what a traveller checks next

A country code answers where. Two things it does not answer are worth checking before you fly. Public holidays close banks, shops and offices and fill trains and roads; the public holidays index on holidaygrid.net covers 46 countries by year. And on a long-haul flight the daylight at the far end is rarely what you expect; sunandmoon.app computes sunrise, sunset and day length for 956 cities from their coordinates.

Frequently asked questions

Look up a code

Browse the country hubs, or search any airport or airline on the home page. The dataset and its licence are documented on the data page.