The canonical link element[1] is a tool used by webmasters to address content duplication problems, ensuring search engines can identify the original source of content. These duplication issues can arise from various factors, including GET-parameters, different hosts or protocols, content management systems, and print versions of websites. Introduced by search engines such as Google[4], Yahoo, and Microsoft[3] in 2009, the canonical link element is placed in the HTML[5] head section or sent via the HTTP header. It serves as a strong hint for search engine[2] ranking algorithms, guiding them to the preferred version of a webpage. However, it’s worth noting that search engines may choose to ignore these links if it benefits the search results. Implementations include semantic HTML and self-hyperlinks, with examples provided in HTML code and HTTP response headers.
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.