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Non-Canonical Pages

Non Canonical Page - Raptor SEO Data

Canonical pages have a canonical tag with a self-referential canonical link, these pages are the preferred version of pages on a site. For example, if a site is accessible with and without the ‘www’ we would apply a canonical tag to each page specifying which one is the preferred version. If a page is accessible from multiple URLs, canonical tags are used to determine which is canonical.

The short video below describes what non-canonical pages are, why we show you this data and what it all means. Because we don’t just crawl a site and collect raw data, we analyse that data we are able to produce more valuable summarisations of the raw data to save you time.




What Are Non-Canonical Pages?

A non-canonical page in terms of what the crawl data we summarise in this section means is a page that has a canonical tag that does not match the URL of the page. For example, this page has the URL:

Whereas if the canonical tag were to be this (see below), the page would be non-canonical:

<link rel="canonical" href="">

In this is example the canonical URL includes the www, whereas the page does not.

The criteria for non-canonical pages in this dataset are:

  • HTML page
  • With a canonical tag that references another URL
  • Returns a status code of 200

If the page is missing the canonical tag, then we cannot determine if it is not canonical.


How Do Canonical Tags Work?

A canonical tag sits in the <head>…</head> section of the HTML of a webpage and looks like this:

<link rel="canonical" href="">

To break this down further:

<link rel="canonical"

This is a rel canonical tag and it specifies that the contents specified is the canonical  version  of the page.


This determines that this is a link.


This section specifies the canonical link itself.


This closes the tag.


Canonical Duplicate

If a page is accessible from multiple URLs such as with and without the www or from http and https, these would be considered canonical duplicates. These exist on every site and are handled by both canonical tags and often redirections, that force only the canonical version to be accessed. For example, if you click the link below:

It will redirect you to:


Duplicate Content

Duplicate content is where a page contains all of the same content as another page or a significant majority of it such that it is not unique. You may for example use a duplicate of a product page that has only a few different components and add a canonical tag linking to the home page to ensure that Google know which the preferred version is.

This is often done for custom landing pages for paid advertising campaigns. You could even do this and link to an external site.


What You Can Do with Non-Canonical Page Data?

Typically, you will use this data to ensure that:

  • The non-canonical page is not listed in an xml sitemap
  • To identify canonical errors
  • (for the most part) ensure that the non-canonical page is not indexable
  • To ensure that (where required) redirects are setup to prevent non-canonical pages from being accessible

This guide is part of an extensive series of guides covering the data that we show in the summary tab of our SEO reporting feature. The following list of links shows all of the categories of data guides, videos and tutorials that we have. If you have any feedback on this or anything else, please fee free to get in touch: