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Canonical (Canonical-Tag)

What is a Canonical (Canonical-Tag)?

A Canonical (Canonical-Tag), also called Canonical link or Canonical attribute, is a link in the source code of a web page and points to the so-called canonical URL that should be given preference in the index of Google and other search engines. If page content can be accessed via several URLs or if different pages with similar content exist – for example a mobile and a desktop version – the Canonical tag indicates which page is the preferred version and thus should be crawled with priority.

What is the purpose of a Canonical (Canonical-Tag)?

  • It avoids duplicate content in dynamic URLs: Product variants in onlineShops, for example, can be accessible via the actual URL and via a dynamic URL (e.g. with attached session IDs).
  • It prevents identical content from being accessible under several URLs, e.g. with and without preceding www in the URL.
  • If identical content is available in different formats (e.g. PDF, print version), it indicates the preferred version.
  • In the case of identical content on multiple domains, it identifies the preferred domain.

Canonical URL Checker

With the Canonical URL Checker you can check if a website uses Canonical tags:

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