Our data

Rel canonical is a tag in the header of your HMTL that tells search engines which piece of content is the original and which one is a duplicate. It has been created in order to avoid duplicate content issues and optimize your SEO.

Indeed, some pieces of content can appear in multiple places of your website and thus be seen as duplicate content. Duplicate content is actually deeply penalized and rel canonical provides search engines a way to know which version of the content is the original, gives credit to that primary one, links the copy to the right URL and thus displays the good version in the search engines results.

Canonicalization is essential to create a well optimized website and offers a better user experience; users do not have to choose which version of a page is the best or more likely to be the original.

OnCrawl offers the possibility to spot your rel canonical easily.

Here you can see if your canonical are set up correctly, and if they are matching or not. Like our other features, you can access deeper details.

Best practices to canonical

There are multiple situations where canonical should be used for duplicate content:

  • Multiple URLs: e-commerce websites which offer filter options like prices, sizes, colors, categories have a lot of URLs with duplicate content
  • HTTP, HTTPS, WWW: a search engine can see http://www.mywebsite.com, https://mywebsite.com and https://www.mywebsite.com as different websites and will index them as such
  • Mobile URL: mobile URLs like m.mywebsite.com are seen as duplicate content
  • Country URL: content remains the same even if you are using specific country URLs. However, if the language is different, you may want search engines to offer separate results
  • Session ID URLs, breadcrumbs links, printer friendly versions, permalinks: they are automatically generated

How to optimize your content with rel canonical?

First of all, you need to choose which URL is the main one and then insert at the top of your prefered URL <head> section:
<link rel=”canonical” href=”http://www.yourdomain.com/your-main-url/” />
Most of CMS solutions integrate that tag automatically. Here are the few rules you should respect if you want to integrate your rel canonical correctly:

  • Verify that the rel canonical target exists otherwise you will get a 404 error
  • Check that the rel canonical target does not have a noindex robots meta tag
  • Insert the rel canonical link in either the <head> of the page or the HTTP header and not in the <body>
  • Include no more than one rel canonical per page. When more than one is specified, all rel canonicals will be ignored
  • A large part of the duplicate page’s content should also be on the canonical version


For any questions about the rel=canonical, feel free to drop us a line @Oncrawl_CS

You can also find this article by searching for:
URLs canónicas, contenido duplicado
URLs canoniques, contenu dupliqué

Did this answer your question?