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Canonical Tags: An Indispensable Element For Your Website

Top 5 most Common Mistakes
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Canonical Tags: An Indispensable Element For Your Website

Canonical Tags: An Indispensable Element For Your Website
Canonical Tags: An Indispensable Element For Your Website


A canonical tag (also called rel=canonical) is a piece of HTML code that defines the major version of a number of duplicate or similar pages. If you have several pages on your website that are very similar, it is therefore wise to set a canonical tag. This lets the search engine crawler know which version is the most important and should therefore be indexed. At the same time, this prevents ‘duplicate content’. 

You can read why canonical tags are important and how you can implement them in your website in this blog.

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The importance Of Properly Implemented Canonical Tags

When the search engine crawler comes by to crawl multiple pages that are very similar – and no canonical tag is set – it is difficult for the crawler to judge what the main page is and which one should be displayed in the SERP (search engine). results page). This in turn has adverse effects on your SEO . 

In addition, there are two other important issues that can arise when using the canonical tag incorrectly. Firstly, you run the risk that the ‘crawl budget’ will run out (this is especially important for large webshops). As a result, not all pages may be crawled and therefore not displayed in the SERP. Second, a big risk is that the search engine itself decides which URL to display in the SERP. If this happens, it may just be the wrong URL

The Emergence Of Duplicate Content

Duplicate content is a lot more common than you might initially think. To understand in which situations it is important to set a canonical tag, we give a few examples of how this is created.

  1. Copied Content
    A potential problem that often comes up with e-commerce websites is related to product information. When many different webshops sell the same product, and use the standard text written by the manufacturer, this results in the same content (or duplicate content) on multiple websites.
  1. HTTP/HTTPs & with or without WWW
    When your website has separate versions, such as ‘www.hemdvoorhem.nl’ and ‘hemdvoorhem.nl’ that have the same content on the page, then there is duplicate content. The same goes for http:// and https://. 
  1. Variations in the URL
    URL parameters (such as filtering pages, analytics, and click tracking) can cause problems. You can read a good example of this at the Hemdvoorhem.nl webshop later in this blog.

How To: Implement Canonical Tag

There are five different ways to specify canonical URLs, namely:

  1. HTML tag (rel=canonical)
  2. Site map
  3. 301 redirect
  4. Internal links
  5. HTTP header

By far the most common method of setting the canonical tag is through the HTML tag. Below you can read how it can be implemented for the widely used CMS WordPress.

Implement Canonical Tag In WordPress

Setting a canonical tag in WordPress is very easy with the Yoast SEO plugin. Convenient: self-referential canonical tags are automatically added by this plugin.

At the bottom of every page – in the Yoast SEO menu – you will find the field under the heading ‘advanced’ to enter the canonical tag.

Implement Canonical Tag In WordPress
Implement Canonical Tag In WordPress

Check If The Canonical Tag Ss Implemented correctly

To check whether the canonical tags for website are set correctly, we go through the step-by-step plan below:

  1. Check if the canonical tag of the main page points to itself
    . You can for example use the Google Chrome extension ‘ Inspect Canonical ‘ to see it at a glance. Alternatively, you can also very easily display the page source (control + u) and search for ‘canonical’. If the main page has a rel=canonical pointing to itself, it is set correctly.
    In this case the canonical tag looks like this: <link rel=”canonical” href=”https://www.hemdvoorhem.nl/poloshirts” />
  1. Open a filter page and check whether it refers to the main page
    . Since we only want the main page to be indexed and thus found in Google, it is important that the filter pages are provided with a canonical tag that refers to the main page (in this case: https://www.hemdvoorhem.nl/poloshirts). To check this you can for example go to the 2nd page with products, or apply another arbitrary filter such as the ‘tight fitted fit’.
    In this example, we will go to page 2, making the URL look like this: https://www.hemdvoorhem.nl/poloshirts?sort=orderby-asc&ppage=72&page=2
    To check if this filter page has a canonical tag pointing to the main page, let’s dive back into the page’s source code and search for ‘canonical’. We see that the same tag is set here as in step one, which means that it is correct.

Top 5 most Common Mistakes

Canonicalization is a complex subject, so there are many misunderstandings about how to properly apply it. A top 5 most common mistakes:

Error #1: Blocking the canonized URL through the robots.txt

When a URL is blocked in the robots.txt, it means that it cannot be crawled by Google. If a canonical tag has been added to this page, it means that Google cannot read this tag. This in turn prevents Google from passing the accrued link value from the non-canonical to the canonical page.

Error #2: Setting the canonized URL to ‘noindex’

Never combine the ‘noindex’ and ‘rel=canonical’ tags, as these instructions are contradictory.

Good to know: Google usually prioritizes canonical tags over ‘no-index’. If you don’t want a URL to be indexed and canonized, it’s better to use a 301 redirect. 

Error #3: Setting a 4XX HTTP status code for the canonized URL

Setting a 4XX HTTP status code for the canonized URL has the same effect as using the ‘noindex tag’, namely: Google cannot see this canonical tag, so no link value is passed to the canonical version.

Error #4: Setting multiple rel=canonical tags

If you have set multiple rel=canonical tags, chances are they will be ignored by Google. This is usually caused by the tags being entered in multiple places. Think of a plug-in, the theme or via JavaScript. 

Error #5: Using Rel=canonical in the <body>

It is important that rel=canonical only appears in the <head> of the page. Does it appear in the <body>? Then it will be ignored by Google.

Need help?

The specialists of the online marketing agency Digitalhaiyaar have years of experience with canonical tags and are happy to help you with your (technical) SEO or online marketing issue.

Contact us today for free advice.

Digitalhaiyaar is an enterprising online marketing agency. Through various expertise, we therefore strive to always achieve the maximum return for both B2B and B2C customers.

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