Language tag syntax

The full BCP47 syntax is in-depth enough to mark extremely specific language dialects, but most usage is much simpler.

A language tag is made of hyphen-separated language subtags, where each subtag indicates a certain property of the language. The 3 most common subtags are:

Language subtag

Required. A 2-or-3-character code that defines the basic language, typically written in all lowercase. For example, the language code for English is en, and the code for Badeshi is bdz.

Script subtag

Optional. This subtag defines the writing system used for the language, and is always 4 characters long, with the first letter capitalized. For example, French-in-Braille is fr-Brail and ja-Kana is Japanese written with the Katakana alphabet. If the language is written in a highly typical way, like English in the Latin alphabet, there is no need to use this subtag.

Region subtag

Optional. This subtag defines a dialect of the base language from a particular location, and is either 2 letters in ALLCAPS matching a country code, or 3 numbers matching a non-country area. For example, es-ES is for Spanish as spoken in Spain, and es-013 is Spanish as spoken in Central America. “International Spanish” would just be es.

The script subtag precedes the region subtag if both are present — ru-Cyrl-BY is Russian, written in the Cyrillic alphabet, as spoken in Belarus.

To find the correct subtag codes for a language, try the Language Subtag Lookup.