Glossary
Referrer-Policy
A header a site sends to control how much of its URL is passed on when someone follows a link away from it.
The policy ranges from no-referrer, which sends nothing, through origin-when-cross-origin, which sends only the domain, to unsafe-url, which sends the full path to anyone. Browsers now default to strict-origin-when-cross-origin when a site sets nothing, which is why referrer data got noticeably less useful without anything changing on the receiving end.
The reason is privacy rather than analytics. A full referrer leaks the path of the page somebody was reading, which on a search page or a private document is information the destination has no business receiving.
For anyone measuring links, the practical consequence is that the referrer will tell you the domain at best, and often nothing. Tag the link instead.
