What Is A Canonical Tag? Canonicalisation Explained

Canonical Tag

Welcome back everybody. In this weeks Spoonfed guide, I’m going to be talking about a term that evaded me for quite some time when I was starting off in my SEO journey; the canonical tag.

I, like many an SEO, was looking at that MOZ Site Crawl Report and seeing all of those pages flagged as “Missing Canonical Tag”, thinking to myself “what in the name of God is a canonical tag?”.

Countless Google searches later, a few eBooks and a linguistic lesson and I think I finally cracked it!

Ladies and gentlemen, welcome to the Spoonfed SEO guide for Canonicalization!


What is a Canonical Tag?

According to those good people at MOZ:

A canonical tag (aka “rel canonical”) is a way of telling search engines that a specific URL represents the master copy of a page.

This involves a little snippet of code like the following taken from our recent post on 301 Vs 302 redirects:

SpoonfedSEO Canonical Tag

Essentially, a canonical tag is used to prevent duplicate content issues. An example of this might be if a publisher wants to post one of your previous blogs on their site.

This would create two duplicate pages, your original post and the new publishers post. Now if they have a much more authoritative site than you, there could be fears that their page might start ranking ahead of your for this post.

A way to prevent this from happening is by requesting them to place a canonical tag on the post, directing back to your original post.

This would then essentially tell Google that we know this is a duplicate post and we don’t want it to rank, we want to give all the credit to the original post that the canonical references!

Bippity boppity boo, everybody’s happy!

Why Does Canonicalisation Matter?

Duplicate content will always be an issue for websites. You are going to have different URL variations for your pages. There are going to be pages flagged as having duplicate content.

The search crawlers will have to sift through these pages, potentially missing what should be the master version of a page and possibly causing issues for your SEO.

Canonicalisation helps with this issue and points crawlers in the right direction; mitigating duplicate content issues and ensuring the right page is the one that gets indexed.

What URL Variations?

Now, I know what you’re thinking, “Why would anyone have different variations to their URL’s?” And you wouldn’t! Intentionally..

From a users perspective, your homepage is your homepage and there is only one version of this page.

However, from a crawlers perspective, they might see it differently and see variations such as:

  • http://www.yourdomain.com
  • https://www.yourdomain.com
  • http://yourdomain.com
  • https://yourdomain.com
  • http://yourdomain.com/index.php
  • https://www.yourdomain.com/html

To you, these are all the same page. To Google, each URL indicates a unique page. Which is why we use the canonical tag, telling Google that all of these are duplicates of each other, and there’s only one that we want to rank.


When to Use Canonical Tags

Self Referencing Canonical Tags

A self-referencing canonical tag is exactly as it sounds; a canonical tag pointing to itself. This might not always be necessary but it avoids any potential duplicate content issues with pages down the road.

I’m a firm believer in self-referencing canonical tags! The good news is, if you use WordPress, then Yoast automatically adds self referencing canonicals to your pages.

God I love Yoast!

Redirects Vs Canonical Tags

You will likely hear this argument a lot. I have done an entire post already about the difference between 301 and 302 redirects but there’s a lot of people who think that redirects and canonicals do the same thing. They don’t. Do not listen to these people!

If you redirect one page to another, you are effectively closing down that page and sending both users and crawlers to a new page. This means that nobody will be able to visit the first page.

A canonical lets all the users and crawlers visit both pages but crawlers will identify the canonicalised page as the authoritative page.

These are two very different outcomes so you need to be able to identify situations that require a canonical tag vs situations that require a redirect.

That’s a Wrap

On that note, I think we’ll leave it there folks!

So you now (hopefully) now what a canonical tag is, why you need to use them and also when not to use them!

As always, if any part of this SpoonfedSEO guide was un-clear, then please comment below or get in touch through our contact form.

Our goal is to create content that anyone can understand and learn from. If you have any particular topic you would like some help on then let us know and we’ll help in any way we can!

This is Spoonfed SEO, your easily digestible digital marketing blog!

‘Till next time!

Author: Brian C

Brian is an SEO Manager for a leading Irish digital agency. With years of experience across Social Media Management, Content Development and Strategy and SEO for clients across a diverse portfolio, Brian shares his insights to make digital digestible for everyone.