Everything You Need to Know About Canonical Tags

Website owners, especially large eCommerce website owners, have always struggled in battling duplicate content issues. Depending on the CMS settings, server settings, and the handling of query parameters, duplicate content can be a big pain in the, you know!

In my professional experience, and readings, I have seen the following commonly occurring duplicate content issues:

  1. Same URL with separate versions. Such as first letter uppercase versus all lowercase.
  2. Query parameter URLs with the exact same content.
  3. On rare occasions, cross-domain duplicate content. This is more true for organizations owning more than one domain.

There are multiple ways to handle duplicate content, but for this post, we’re going to be discussing everything you need to know about canonical tags.

Let’s get started!

What Is a Rel Canonical Tag in the First Place?

Rel canonical is an invention of a joint collaboration between Google, Yahoo, and Bing. Precisely, it’s purpose was to allow website owners & coders to handle duplicate content issues better, and in return, help search engines understand which page they’d prefer to rank.

How Does Duplicate Content Issue Rear Its Ugly Head?

The great thing about the internet is the constant propagation of online content! However, a significant potential drawback for website owners, knowingly or unknowingly, who are serious about SEO, is the dissemination of duplicate content. For example:

  1. https://homepage (primary URL) can have the same exact content as
  2. http://homepage (without https), which in turn, can have the same exact content as
  3. https://www.homepage (with www)
  4. https://homepage/home
  5. https://homepage?search=homepage
  6. so on and so forth

So, How Can Rel Canonical Help? And How to Implement It?

Continuing with our example URLs, let’s say that the primary URL is the one you want to get all the SEO credit, and is also the one that you want to be displayed within the SERPs. Strictly using rel canonicals, what you’d need to do is:

  1. On your primary URL, implement a “self referential canonical**” (continue to follow just a little down to the screenshot, and you’ll get it)
  2. On all your other URLs, you’ll have to point your rel canonical to the primary URL.
  3. The same concept applies to cross-domain duplicate content issues as well.

Adding a rel canonical is actually not that hard. See screenshot below for reference.

rel canonical tag example
Screenshot from the source code of Now because the homepage is pointing the rel canonical to itself, it’s called a **self-referential rel canonical.

As you can see, the code itself is not complicated! However, if you need this in a more general format, the syntax for implementing a rel canonical is as follows:

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

The code for rel canonical needs to be within your <head></head> section. Typically, it’s almost always where you have the code for your <title></title> tag, meta description, etc.

What Are the Top 2 Best Practices for Implementing Rel Canonical?

  1. Always, and always implement a self-referential canonical to the primary URL/preferred URL, you want to get all the SEO credit, and the one you want to be displayed in the SERPs. This includes your homepage. In fact, it’s important to do this on the homepage, as we know it can end up with multiple variations.
  2. Stick to a standard: This is indispensable! You cannot end up canonicalizing page 1 to page 2, which in turn canonicalizes to page 3. To make things more complicated, page 3 might canonical to page 1. This is an extremely bad practice, and can do you more harm than good.
    In general, keep it simple.
    a. Have all the duplicate versions canonical to the primary/preferred version.
    b. Have the primary URL do a self-referential canonical to itself.
    You have to “avoid mixed signals.”

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Other Commonly Asked Questions About Canonicals

Can Canonical Tags Pass Link Juice?

Yes, it can. In most cases, it will. But it’s not a guarantee.

Will Google Always Follow the Canonical Tags? As In, Will It Understand It?

For the most part, Google does. Unless, for some reason, it can’t. Again, you have to remember that it’s not a guarantee. That said, it shouldn’t’ discourage you from implementing a canonicalization standard — so to speak, within your company/organization.

But, if I Really Want to Know, How Can I Make Sure Google Has Read My Canonical Tag?

The best source for this information is Google itself. Head over to Google Search console, Inspect a URL, and expand the “coverage” drop-down. Google Will provide you with canonical Details. See the attached search console canonical

What About Cross-Domain URLs?

The same concept applies. Except, in this case, the URLs will be from different domains. Say, for instance, https://domain1/page1, had the same content as https://domain2/page2, you’d have to execute similarly. Pick a primary version and apply a self referential canonical, and in the other version, point the canonical to the primary version.


Duplicate content issues can end being very pervasive, so you need to stay on top of it, for optimal SEO performance. My personal choice to handle duplicate content issues is the combination of implementing 301 redirects + canonicals, a post for another day. However, I hope that after reading this one, you learned everything you need to know about canonical tags — at least, to get started!