ISO 639-1 Language Codes

ISO 639-1 Language Codes are the two-letter codes that identify human languages in a standard way, such as en for English, fr for French, and de for German.

ISO 639-1 is the part of the ISO 639 standard that assigns a short, two-letter code to each major language. These codes are the language half of every hreflang annotation, which is why getting them right is essential to international SEO. They are always lowercase by convention and always two letters.

en  English
fr  French
de  German
es  Spanish
it  Italian
pt  Portuguese
nl  Dutch
ja  Japanese
zh  Chinese
ar  Arabic

In hreflang, the language code can stand alone (hreflang="fr" targets French speakers anywhere) or combine with a region code from ISO 3166-1 Alpha 2 to target a language in a specific country (hreflang="fr-ca" targets French in Canada). The format is the language code, then optionally a hyphen and the country code. The region part is uppercase by convention, though hreflang is not case sensitive.

A few codes trip people up because the code does not match the English name of the language. The code for German is de (from Deutsch), not ge. Chinese is zh, Japanese is ja, and Greek is el. Using en-UK is another common mistake: the correct country code for the United Kingdom is GB, so it should be en-gb. Picking the wrong code means search engines cannot match your page to its intended audience, which is why hreflang errors so often trace back to a bad language or region code.

Related: Language Targeting, x-default, Hreflang and International SEO guide, Hreflang best-practice scenarios