A canonical link element is an HTML element that helps webmasters prevent duplicate content issues in search engine optimization by specifying the "canonical" or "preferred" version of a web page. It is described in RFC 6596, which went live in April 2012.
A major problem for search engines is to determine the original source for documents that are available on multiple URLs. Content duplication can happen in a many ways, including:
Duplicate content issues occur when the same content is access...