Rel Canonical SEO Guide: What it is and How to use it?

Rel Canonical and SEO have gone hand in hand since 2009 when the major search engines decided to solve one of the biggest problems every SEO consultant faces on a daily basis: duplicate content. Despite being one of the simplest concepts of SEO, Rel Canonical is still considered a difficult subject by many today. Let’s see in this guide how and when to implement it on our projects.

What is Rel Canonical

It is an HTML element that indicates to the crawler of search engines, such as GoogleBot , that a page is a copy of another and that all the importance must be transferred to the canonical page, thus preventing duplication of content.

Through the rel canonical, the webmaster suggests to the search engines the preferred URL that he deems most appropriate in relation to the content that the crawler is analyzing on a particular page.

So it is not to be considered a directive but an advice given by the webmaster to simplify and improve the spider’s understanding of our site.

When to use canonical rel?

When there are duplications to be resolved.

More simply: if your site contains multiple pages with identical or similar content, you must use the rel canonical link to avoid the risk of penalties.

In principle, rel canonical should be implemented whenever the same content can be reached via different URLs.

We can therefore identify the following cases for its use:

  1. when the same content is provided by multiple URLs;
  2. when similar content is provided by multiple URLs.

Practical example : if our goal is to have the contents of page X indexed, but at the same time we want these same contents to be present also on page Y, to avoid duplication problems, in page Y it is necessary to implement a rel canonical link to the page X.

It is in this way that we suggest to Google which page is to be indexed and to which all authority must be transferred (in this case page X).

Let’s now see some particularities about its use:

  1. The rel canonical can be used cross domain, i.e, between different domains or between subdomains, just like the 301 redirect.
  2. It is possible to canonicalize from http URLs to URLs in https protocol and vice versa.
  3. Search engine crawlers must be able to access the page that contains it in order to detect it, so it is important not to block crawling through robots.txt.
  4. Can be inserted into HTTP headers.

How do you implement a canonical link?

Now that we have seen when rel canonical is used and we know the answers to the most frequent questions and doubts regarding its use, to implement it on your site you need to specify the following syntax in the head tag of the web pages:

link rel = "canonical" href = "" />

As you can see, the syntax to use is quite simple and it is sufficient to replace the example URL with that of the canonical page of our site.

Please note: all the main CMS (WordPress, Joomla, Magento, etc.) now have plugins or components capable of configuring and automating the management of the rel canonical.

Despite the practicality and effectiveness of these tools is beyond question, my advice is to check the effects at the code level, in order not to find yourself in situations that can nullify the benefits of the rel canonical link.

For more information on its implementation, I refer you to the official Google Rel Canonical documentation.

What is the difference between a rel canonical and a 301 redirect?

The main difference concerns the impact on user navigation: the 301 redirect directly affects the user experience as the user is redirected to another URL than the starting one.

The canonical, on the other hand, is a directive that only affects the crawler of search engines as the user is not redirected and therefore does not perceive its existence.

From an SEO perspective, both the rel canonical and the 301 redirect are directives that indicate to search engines which is the preferred version of a web page, or rather the one we want to be indexed to avoid multiple scans.

However, having a direct impact, the 301 redirect is certainly a stronger signal in this sense.


Very useful to minimize the problems of duplicating resources upstream, the rel canonical is a tool that every SEO must know how to use to save crawl budget and improve the indexing of a site on Google.

If you have any doubts or questions regarding Rel Canonical and SEO please feel free to ask in the comments.

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