Using Canonical Tags for SEO – in 2021

SEO Article
20 mins

Google doesn’t much like duplicate content. O.K well in some cases it will accept and tolerate it, but overall it considers it more of a challenge.

Why? It finds it hard to choose which page to index and doesn’t know which version to rank. This is where canonicals can help.

In this article we will explore what they are and how you can use them to improve your SEO (search engine optimisation).

What are canonicals?

Canonicals provide website users with a way of solving multiple page issues by inserting a snippet of HTML code within the <head> section of a website. The HTML code is used to specify which is the master version of the same duplicate content to make it indexable, which ultimately improves your SEO.

Why are canonicals important?

If you don’t tell Google which version of a page you want to appear on the search engine results page, Google will decide for you. They also don’t know whether to focus ‘equity’ on one page or split it equally between multiple duplicate pages.

Google spiders could waste time crawling through duplicate content, which could result in them missing some of your more unique and high quality content that you really want to get seen. This is why it is so important to point Google in the right direction and optimise your website for SEO.

How do I know if I need to use canonicals?

A lot of people assume that they don’t have duplicate content issues and that they don’t need to worry about canonicalizing their website. However, in a lot of cases, website users can have duplicate pages without even realising. Whilst we can visually see our different website pages, Google’s spiders can’t. Instead, they crawl all URL variations as separate pages, so depending on the size of your website, you could have duplicate website content that you never even knew about.

An example of this is www and non-www variants. Although and take you to the same page, Google reads this as two separate pages and so you need to instruct Google which variant to index.

Below are just a few examples of how your website might have duplicate content:

  • Parameterized URLs for search parameters
  • HTTP and HTTPs variants
  • With and without trailing slashes
  • With and without capital letters

When implementing this on your website, note that it isn’t a solution to duplicate content, as the two variations of the page still exist. This can have negative effects on Google Analytics, who can’t read canonical tags so still treat the pages separately. Click for more information on how canonical tags impact Google Analytics.

How do you implement canonical tags?

The simplest way of implementing the tags is using a rel=canonical tag. You can do this by adding the code to below the <head> section of your duplicate pages.

<link rel=“canonical” href=“” />

Feel free to add self-referral tags on the canonical page itself page itself – this will help tell Google that the page they are currently on is the master page.

You can also optimise your website sitemap for canonicals. Google advises only to include canonical pages in your sitemap because Google uses this as a guide for the most important pages on your website.

How can I tell if my website has canonicals?

You can check whether a specific website page has been given a canonical tag by viewing the source of that page. To view the source of a page, press Command+F (mac) or Control+F (windows), and then search for ‘canonical’. It should look like this.

Hopefully this guide has helped you feel confident implementing canonicals into your website and how doing this will ultimately improve your SEO. For SEO tools that will help you analyse things like canonical tags, check out our blog post ‘SEO Powersuite Review’.

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