Hreflang - Supported language values

Use hreflang for language and regional URLs

The value of the hreflang attribute identifies the language (in ISO 639-1 format) and optionally the region (in ISO 3166-1 Alpha 2 format) of an alternate URL. For example:

de: German content, independent of region
en-GB: English content, for GB users
de-ES: German content, for users in Spain

<link rel='alternate' hreflang='x-default' href='' />
<link rel='alternate' hreflang='en-gb' href='' />
<link rel='alternate' hreflang='en-us' href='' />
<link rel='alternate' hreflang='en' href='' />
<link rel='alternate' hreflang='de' href='' />