What are Canonical Link Elements.

Google along with other reputed search engines has announced support for Canonical link elements that help website owners’ deal with duplicate issues. Websites often produce pages with the same content but at times this practice is unintentional. Hence, it is necessary for web developers to design sites where the URL appears different even while the contents are identical. An instance being the e-Commerce activities where the dynamic string called “Session ID” differentiates one user from the other for session tracking. From the perspective of search engines, these are all diverse URLs and would be indexed. This often leads to stupendous amount of duplicate content in the search index –same web pages having different URLs.


Normally search engines use sophisticated and proprietary algorithms to detect duplicate content in order to present the search consumer with as many useful results as possible. The differences in proprietary algorithms used among various search engines result in diverse form of URLs to be presented to users. To tackle the resulting inconsistencies, major search engines have supported a special index feature termed “Canonical URL Tag” which gives the Webmasters an opportunity to set a “preferred” name for a page. Though the Webmasters’ preference hint would be strongly honored, other signals might also be used to evaluate the final layout when multiple forms exist in the index. In case the Canonical URL creates “404 Error” during crawling or if it specifies a URL on different domains, the Canonical tags would then be ignored.


The Canonical element represents a timely relevant and positive partnership between major search engines. This method guarantees more consistency with regard to treatment of duplicates among all the search engines. Moreover this feature offers more control to website designers on how their sites would be represented within the search indices. To migrate to a completely different domain permanent “301 Redirects” are more appropriate. Google, Yahoo and Microsoft are supporting the new Canonical link element to help in the identification of links to one’s website. This also brings in more traffic as web users tend to opt for those websites where more than one link exists on the same content. The Canonical link could be used in the search engine indexing while the site map URLs would be used whenever a tie exists between multiple URL links.

The Word Press 2.9 version has integrated the “rel=” Canonical link element which is displayed between the “Head Tags” but only on the single post pages. However, “Drupal” has not supported the “rel=” Canonical link element. Website owners using Word Press may have their “rel=” Canonical link element on all the pages of the blog such as home page, content, tag and are also found on other pages of the blog. This informs the search engines which link to use for all similar content that otherwise may be labeled as duplicate content. To ensure that all pages inform search engines which link to use, one needs a plug-in to help with SEO. Additionally, the Canonical links significantly improve the SEO of the blog resulting in more high quality traffic.

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