Canonical URLs

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The attribute <link rel=”canonical”> allows to specify the canonical, that is the main version of the document to the search bot. This attribute needs to be attached not only to the main promotion page of the Internet project, but also to its doubles.

If one page is available at several URL addresses, search engines recommend using canonical links specifying the address of the main page – the preferred one for indexing.

They are set using the LINK tag with the attribute rel = “canonical” in the page HEAD and are supported by all known search engines, including Yandex and Google. The attribute rel = “canonical” helps not only to exclude all duplicate pages from the search results, but also to concentrate the valuable reference weight properly.

What is The Canonical Page?

Sometimes the same page of the site is available at several URLs. For example:


There are several causes of doubling, but the most widespread is including the material in more than one category (as in the example above). For such cases search engines began to support the attribute rel=canonical so the webmaster themselves could specify the preferable (main) page and force the bot to ignore other doubles. Use of the attribute is very profitable for promotion even if you do not use function of including material in several categories (sometimes doubles are made due to the shortcomings of CMS itself).

Why CMS Creates Doubles

There is no reason to believe that the content management system generates duplicate pages intentionally. Typically, such copies are created due to incorrect configuration of CMS. The most common reasons for doubling are:

  • creating archives of old articles;
  • open links to documents in PDF-version (available for printing);
  • wrong site structure, adding the same pages to different categories;
  • dynamic URLs (typical for online stores).


Canonical links help to get rid of duplicate pages and concentrate the static weight in the right place. Thanks to the attribute rel=canonical, search engines index only real pages, and you will see only the real number of unique pages of your site when analyzing it (not as before, when you added 100 materials, and 500 pages get into the Google index, but none of them takes a proper position in the search results).