Deutsch
hreflang & language tags

Language code (ISO 639-1)

Also known as: ISO 639-1

A language code, in web and SEO use, is a short identifier for a language, usually the two-letter code from ISO 639-1 such as de, en or fr. It appears in hreflang annotations, in the lang attribute and in language tags.

How is a language code built?

On the web, language tags follow BCP 47, published as RFC 5646. A tag consists of a language subtag and optional further subtags for script and region. For languages that have a two-letter ISO 639-1 code, only that code is defined in the IANA registry. The RFC recommends lowercase for language codes, a capitalized first letter for script codes such as Cyrl, and uppercase for region codes. Tags are treated as case insensitive.

Google’s hreflang format takes the language code in ISO 639-1 format followed by an optional region code in ISO 3166-1 Alpha 2 format. Specifying the region alone is not valid. Google adds that it does not rely on code-level language attributes to determine a page’s language, so the visible content has to be in that language.

Examples

Value Meaning
de German
en-GB English for users in the United Kingdom
zh-Hant Chinese in Traditional script
zh-Hans-US Simplified Chinese for users in the US
HTML
<link rel="alternate" hreflang="en-GB" href="https://example.com/en-gb/" />

Common mistakes

  • Using a region alone, such as GB, in hreflang. Google calls this invalid.
  • Using UK for the United Kingdom. Google ignores it, and the region code is GB.
  • Using EU or UN, which Google ignores as reserved values.

FAQ

What is the difference between a language code and a country code? A language code names the language and a country code names the region. In hreflang the language code comes first and the region follows.

Is a language code without a region enough? Yes. de is valid and covers German in general.

Sources

  1. Tell Google about localized versions of your page – Google Search Central (updated 21.09.2026)developers.google.com
  2. RFC 5646 – Tags for Identifying Languages (BCP 47), September 2009rfc-editor.org
  3. Managing multi-regional and multilingual sites – Google Search Centraldevelopers.google.com
  4. ISO 639-1 – Wikipedia (secondary)en.wikipedia.org

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