Canonical: what is a canonical URL and how to use it?

Duplicate content is often complex to manage to optimize the performance of a site and the positioning of pages on search engines like Google. Fortunately, canonical URLs can solve some of these problems and improve the SEO performance of articles that span multiple pages.

What is the canonical tag?

The canonical tag is an HTML code used in natural referencing to indicate which is the main page when a single content is spread over several pages. A canonical URL is especially useful for paginated articles, such as when reading continues on pages 2 and 3. With this tag, it is possible to indicate which is the parent page.

When to use the canonical tag?

The rule for using the canonical tag is simple: it is a question of using it as soon as pagination is possible or probable. In practice, this occurs in three scenarios: when content is spread over several pages, when pages are dynamically generated, and when the same content has different URLs.

Indeed, it sometimes happens that content is voluntarily cut into several pages to improve reading, lighten the weight of each page (for example by distributing the images on several of them) and / or create the opportunity to display more advertisements. This first typology sometimes but not systematically includes tutorials with a parent page and several child pages. But if the topic is unique, then a canonical URL will need to be used in order to tell search engines what the main page of this content set is. If the topics of the child pages are distinct (because specific) from that of the parent page, then the use of a canonical tag will be discouraged.

In addition, dynamically generated pages are also likely to be paginated and therefore require a canonical tag. For example, a forum can be set up so that after 10 posts, a new page is automatically created to host the next ones. Yet these messages will all be on the same topic. That is why it will be necessary to use a canonical URL in order to indicate to search engines like Google which is the first page and which ones refer to it.

Finally, when unique content is present on the web with different URLs, it is also necessary to use the canonical tag. This case occurs most often when the URL varies according to the connection media used by the user. Indeed, a site sometimes uses different URLs for computers and mobiles to adapt the layout or optimize the weight of graphic elements. Thus, the same site can for example be accessible via the following URLs:

• https://www.example.com/
• https://m.example.com/

In this case, it is also a question of indicating to search engines that it is normal that the content of these two (or more) URLs is identical despite the fact that the addresses are different.

How to use the canonical tag?

More concretely, to use the canonical beacon, there are two main ways to do it. The first is to place it in the HTTP header of the page and the second will prefer an insertion in the HTML body of the page. These two ways make it possible to obtain the same result but the second technique is often simpler if the person who performs it does not have advanced knowledge of coding.

Whether in an HTTP header or in the HTML body of a page, the canonical tag is in the HTML form: rel=canonical. It will then be necessary to indicate the URL of the parent page and insert it in it as well as in all the pages whose subject is identical.

To place it in the HTTP header, you must use the following code:

Link: <http://www.example.com/>; rel="canonical"

Of course, the address http://www.example.com/ will have to be replaced by that of the parent page.

To insert the canonical tag into the HTML body of pages, two methods can be used to achieve the same result. The first, for those who master advanced web techniques, is to code the tag directly in the pages. The code to be used is as follows:

<link rel="canonical" href="https://www.example.com/" />

Again, the URL mentioned should be that of the parent page.

The other, simpler technique is to use:

• A CMS with the functionality, such as the CMS Hub,
• An SEO plugin like Yoast SEO or Rank Math.

After their installation, they will then appear an "Advanced" field at the bottom of each page in the administration tool. In this field, it will be enough to indicate the URL of the parent page and the plugin will automatically add the canonical tag in the pages. The latter technique works for dynamically generated pages but not manually created ones. It will then be necessary to add the same URL in the "Advanced" field of the pages of the same subject created manually.

To go further, go through our blogs and website that contains all the tools, information, and strategies essential to make technical SEO one of the pillars of optimizing the performance of your website.