Canonical Tag
The canonical tag (rel=“canonical”) is an HTML element that tells search engines which URL is the preferred, canonical version of a page when identical or very similar content is reachable at several addresses.
In practice
Canonical tags consolidate ranking signals on a single URL and stop similar pages – created by parameters, print views or language variants – competing against each other as duplicate content. Every page should point either at itself or deliberately at the one intended target version.