Hreflang

Hreflang is an annotation that tells search engines which language and region a page targets, so the right version is shown to the right audience. It is expressed as link tags in the page head, or equivalently in a sitemap, each naming a language-region code and the URL for that version. The rules that make it work are easy to get wrong: the references must be reciprocal, so every version points to all the others including itself, the codes must follow the standard format, and the URLs should be canonical. An x-default entry covers visitors who match none of the specified locales. Done well, hreflang prevents the wrong regional page from appearing in results.