What is Canonicalisation and what does it mean for your SEO?

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Owen Whitcombe

Senior SEO Specialist

Canonicalisation sounds like a daunting concept, but it isn’t. This complicated phrase often causes online marketers and web designers across the globe to shudder at the thought of having to tackle a technical problem that involves comprehending this sixteen-letter behemoth.

But it’s really not that scary. We thought it’d be handy to break this intimidating idea down into a bite-size blog post to demonstrate just how simple it really is.

What is Canonicalisation?


Simply put, if you have a canonicalisation issue then you have a problem with your URLs. It means that either your on-page content exists in more than one place or that there are dead pages that exist on your website that you didn’t know about. The duplicate URL problem may be present on a small scale (i.e. a page existing in more than one place) or on a larger scale (i.e. an entire website existing in more than one place) but either way it’s a problem that needs addressing. Here are a few examples of what I mean:

    1. Single page duplication – It could be that your CMS is generating your blog posts in more than one place due to the way that it archives them. E.g: A blog existing at both and
  1. Site wide duplication – It could be that two versions of an entire website can exist simultaneously. E.g: Your site existing at both and This will mean that every single one of your pages has been duplicated.
  2. URLs that you didn’t know about – It might be that your website exists at but does not load at i.e. if a user types directly into a browser’s search bar.

Why is canonicalisation such a big deal?

I know what you’re thinking: “I don’t care – that all sounds a bit too technical to worry about.” or “Surely the more instances of my pages, the better chance I have of getting traffic?”

Unfortunately canonical problems make it a lot harder to rank well in search engines. Here’s why:

    • Indexation problems in search engines – If you have more than one occurrence of the same page, Google’s web crawlers will have a tough time deciding which URL is the correct one to display in search results. This will result in the bots either guessing which is correct or worse not indexing any of them!
    • Unclaimed link juice – It is possible that several other websites are linking to you, but that they are all linking to different URLs despite linking to the same content. If for example your blog posts exist in multiple places as in example 1 above, your content could be earning great inbound links, but a canonicalisation problem will mean that these links are being spread across more than one URL, thus giving link juice to several weaker pages rather than a single strong one.
    • Duplicate content – The Google Panda update first rocked the SEO world back in 2011 by clamping down on identical content being published in more than one place. Since then it has become critical to solve duplication issues, and canonical URLs can result in lower rankings due to this duplicating content.
  • Poor user experience – Imagine you are running an offline marketing campaign that encourages users to type your website directly into their browser. If, as in example 3 above, your website does not redirect correctly, when a potential customer types in your URL without the ‘www.’ then they will see a 404 error page instead of being redirected to your homepage.

So what do I need to do to solve it?

In most instances where canonicalisation is present, you will need to get your web developers to redirect the URLs into just one version. This will usually be solved by either setting up a 301 redirect or by adding new instructions into the .htaccess file that controls how your website’s URLs are generated. 301 redirects should be put in place careful with a fully formed redirection strategy to ensure searches engines continue to find all your relevant web pages.

You can also use canonical tags to indicate to search engines which web page is the one that should be used for ranking purposes. A canonical tag should always be in place even if the canonical tag is pointing to itself. When it comes to duplicate or very similar content a canonical tag which looks like: rel=canonical <link> should be put in place to indicate which version should be considered by a search engine when ranking. Add a <link> tag in the code for all duplicate pages, pointing to the canonical page. This ensure you have created a canonical url, which Google’s developer documents describes as “the URL of the page that Google thinks is most representative from a set of duplicate pages on your site.”

You can use Google Search Console to help you findout if there are any canonical issues that could be affecting your SEO efforts. Here you can find out how Google is interpreting your Canonical URLs.

screenshot of search console

And that’s it!

So that’s canonicalisation 101 – what it is, why it’s important, and what you need to do to solve it.

Hopefully now you can do more than just nod along the next time you hear ‘canonicalisation’ rear its ugly head in conversation.

However if you have a specific technical problem that hasn’t quite been answered here, feel free to drop me an email on and I’ll be more than happy to dig a little deeper to help you banish those canonical demons once and for all! You can also find out how our SEO agency can help your business with all manner of technical SEO related issues.

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Owen Whitcombe

Senior SEO Specialist

Owen has worked in primarily Ecommerce since leaving University. Many years spent in the online sports retail arena before gaining experience in the online catering business then becoming digital marketing manager for national toy company before finding his feet in SEO. As a results driven individual Owen loves nothing more than when we can give…

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