Canonical URL Explained


This has to be one of the more confusing topics within the theme of Search Engine Optimisation, that we have come across – the Canonical URL. This sticky little bugger is quite vague, and almost seems useless and as if it has no use in modern SEO. Don’t be too quick to disavow what this tag is capable of – as we will discuss in this article, there is far more than meets the eye. And even more to be confused by – so enjoy… But before we begin, let us take a moment to question our own understanding of the term; “URL”.


What is a URL?

At its most basic, a URL is the address of a page or document on the World Wide Web. Like the houses and buildings in your home town all have street names and house numbers? Same here, except it is the world’s largest community, the web. Every cat video, soccer-mom cooking blog, porn site, you name it and its there – each with their own address of where they stay.

We all know a URL as something similar to the following structure: “WWW” [dot] {INSERT UNIQUE NAME HERE} [dot] (COM/ORG/CO[dot]<COUNTRY INITIALS> or whatever – Their structure is a cleanly laid-out road-map to finding exactly where on the web the documents that make up a web page, are stored. i.e.:

www = its part of the World Wide Web

[example] = its house number

.com = its neighborhood (and a hint at what its purpose is)


In conclusion, its the thing that makes you either blow up in popularity as, or remain in obscurity, like (Sorry, Jen.)

But how does this relate to the topic, wait, what is the topic? and how are cannons involved?


Canonical URLs

Now that we have a refreshed definition of URLs in our minds, lets discuss the ‘Canonical’ aspect of them. What Canonical URLs aim to do is alleviate the damage that can be done by duplicated content. The damage we are referring to has more to do with SEO than anything else, so make sure you have a current understanding of SEO before reading on.

In terms of SEO, duplicated content is a big red flag to Search Engines. It screams that the site is of low quality and that the person who made it is just out to make the site look full, when in fact there is little unique about the content on it. This, too, goes for content that is duplicated within a single site, and content duplicated across multiple sites. In that case, is there a possibility for a site to need duplicated content? The answer is yes.


When Duplicate Content is Inevitable

The thing is that sometimes there is no other way around duplicated content, and that it may come about because of trying to create a better user experience, not a diminished one. What complicates this is the fact that Search Engines use programs called Crawlers to scan through websites, analyse them, and draw an SEO related conclusion from their findings.

Crawlers are nowhere near perfect systems, yet Search Engines still rely on them to get the job done. They will get confused when a site seems to be mistreating content and leaving duplicates lying around. But sometimes your site will generate Duplicates when there are particular state changes it has to undergo in order to get the right level of user experience. An example of this would be, a basic page but it allows you to change the language, or an eCommerce page that lets you toggle between different currencies.

Essentially, the content does not change, but the state changes mentioned above could result in Duplicates, to which the Crawlers would not react very positively.


What Canonical URLs Do

The main function of the Canonical URL is to leave an indicator within your website’s code, that speaks directly to the Crawlers and telling them which of your pages is considered the most important or primary version of the group. That way the Crawlers can ascertain that while your site may have duplicated content, this has been taken into account, and the most valid page has been flagged. This is highly important in order to avoid being penalised by the Search Engines, and what’s more, this will provide a positive boost to the site’s SEO.



The Web is being molded by Search Engines, into an environment that is focusing more and more on User Experience. Those who do not take these best practices into account will be penalised, it is as simple as that. Knowing what you can do from your side is half the battle of keeping your site in the clear. This article only aimed at explaining what a Canonical URL is, and there will be another article on how to go about integgrating them properly.