Canonical link element explained

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.^{[1] [2]}

Purpose

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 many ways, including:^[3]

• Duplication due to GET-parameters
• Duplication with multiple URLs due to CMS
• Duplication due to accessibility on different hosts/protocols
• Duplication due to print versions of websites

Duplicate content issues occur when the same content is accessible from multiple URLs.^[4] For example,

Notes and References

1. Web site: Specify your canonical. Kupke. Joachim. 2009-02-12. Google. 2012-08-02.
2. Web site: Learn about the Canonical Link Element in 5 minutes. Cutts. Matt. Matt Cutts. 2009-02-15. 2012-08-02.
3. Web site: Link rel=canonical: How to do URL canonicalization right . 2015-10-06 . Audisto GmbH . Tobias Schwarz & Christian Mueller.
4. Web site: Duplicate content. Google. 2012-08-02.