The International Organization for Standardization introduced the first standardized language code system, ISO 639, to represent languages and language groups. The system enabled the international community to successfully identify languages and language families despite a person’s native language.

Language codes are notably used in machine learning, bibliographical referencing in libraries, and representing different language versions of a website. The codes now consist of anywhere from 2 to 4 letters, depending on the ISO code being used.

Types of ISO codes

There are now several ISO 639 codes, each with a specific aim. The ISO 639-1 codes are Alpha-2 codes, and ISO 639-1 was the first code created. There is a total of 136 ISO 639-1 codes for languages all over the world. Examples here are as follows:

• de: German

• es: Spanish

• en-us: English (USA)

• en-gb: English (UK)

It is important to note that some languages also have a two letter country code when a language is used in multiple countries. This is especially important in translation, enabling translation professionals to localize your content and distinguish between Brazilian Portuguese and Portugal Portuguese, for example.

ISO 639-2 codes are Alpha-3 codes. The extra letter allows for more possible combinations and as a result, there are 464 total codes. The list of codes is maintained by the Library of Congress and consists of almost all living languages. ISO 639-2 contains codes for groups of collective languages, like the below examples:

• aus: Australian languages

• bat: Baltic languages

• cai: Central American languages

• gem: Germanic Languages

ISO 639-3 codes are Alpha-3 codes that largely overlap with ISO 639-2 codes. However, ISO 639-3 includes the individual languages from ISO 639-2, as well as extinct, ancient, historic, and constructed languages. These codes do not include the language groups, so many refer to the ISO 1 and 2 codes as “macro-languages” and ISO 3 breaks those down into “micro-languages.”

The ISO 639-3 codes are maintained by SIL International, and according to them, these identifiers were created with the digital world in mind. By having more languages represented by a standard list of codes, it is easier to optimize the languages for the web and have them included on webpages.

Other ISO codes to be aware of

• ISO 639-4 provides guidelines and general principles for language coding and how to use the ISO 639 codes.

• ISO 639-5 is still in progress and only contains 115 collective codes at this time. It expands on the codes in ISO 2, representing language families and groups with an Alpha-3 code.

• ISO 639-6 is the newest coding system developed by ISO and is an Alpha-4 code that allows for distinguishing between language variants. This comprehensive list establishes a hierarchy for languages and a historical timeline like the below for English:

  • eng: English language

  • emen: Early modern English

  • menge: Middle English

  • ango: Anglo Saxon

  • ineu: Indo-European

  • wrld: World