hreflang is an attribute in HTML to mark that the target of links are in a particular language. When combined with rel-alternate, it can be used to mark that another page has the same (or broadly similar) content but translated into another language.
Places using hreflang properly
Places that should use hreflang
- GOV.UK, the UK Government's official website, has content about the relationship of Britain with other countries. That content is often available in those languages. There's no hreflang links between content in different languages.