The Ultimate Guide to Canonization

When your content ranks well in the search engines, you get more traffic, more eyes, and more clicks on your website. That’s the whole point of Search Engine Optimization (SEO), right? You want to optimize your site so that it ranks better in the search engines.

There are lots of simple SEO concepts that are easy to do yourself. For example, choosing the right headings, writing meta descriptions, and selecting strategic backlinks. However, some concepts aren’t as easy to pick up and take some time to master.

Canonicalization is one of those more challenging concepts. But, it is a game changer for your SEO strategy.

What is Canonicalization?

A canonical tag is the HTML that appears at the top of your web page. It tells the search engines which URL is the authoritative source for the content. You may have various versions of the same content each with their own URL. Canonicalization is the use of HTML tagging to tell the search engine which URL is the primary and more authoritative source.

Canonical tags come with a citation which gives the original piece of content credit and prevents your web page from suffering penalties from having duplicate content.

So far, the concept of canonicalization seems simple, right? It boils down to plagiarism rules which we all learned as children. You cannot write your name on someone else’s work. Because the penalties for duplicate content are so harsh, it is crucial to have a canonicalization plan incorporated into your Search Engine Marketing strategy. Get comfortable using canonical tags to prevent duplicate content penalties.

It can be difficult for humans to see duplicate content the same way search engines do. You might have one web page with a specific URL. But, if different versions of the content exist with the same URL, that looks like a straightforward case of plagiarism to the search engine. The solution to this problem is canonicalization.

When Should You Use Canonical URLs?

There are a handful of scenarios where using canonical URLs is super beneficial to your SEO and in protecting you from duplicate content dings.

The first is in the case of having multiple versions of one product. For example, let’s say your ecommerce business sells bathrobes in five different colors and sizes. You should have one URL for the main product page (like this: and then separate URLs for the variation pages which have the other colors and sizes (like this:

The second scenario to use canonical URLs is when you have mobile-specific pages, like a mobile-specific subdomain or an AMP page. Making your website mobile friendly is a huge component of successful SEO. But, you want to make sure your identical content from the desktop page has a separate URL on the mobile-friendly page. For AMP pages, follow Google’s guidelines on differentiating the URL from other pages.

The third scenario that requires canonical URLs is when you have region-specific pages. In other words, geotargeting. Targeting your content to users in different locations can be super useful in your marketing. You can do this by using a regional slug or subdomain and making sure the region-specific pages lead users back to the original copy of the page. An example of a region-specific URL is: What about having content in English on one page and the same content in another language on another page? This doesn’t count as duplicate content and you won’t get dinged for it. You still want to include a canonical tag if most of the content is in the same language.

The fourth and final scenario to use canonical URLs is for self-referential pages. In the backend of most web design platforms, you can set the canonical URL of a newly built page yourself, although most CMS platforms will do this automatically for you. Google has confirmed that although there are automatic canonical URLs available, it is better for your ranking to create them yourself.

How to Set Your Page’s Canonical URL

There are several different ways you can set your own canonical URLs, and there are pros and cons to each. However, there isn’t one method that is proven more successful or better than the rest. It comes down to which is easier and most comprehensive to you and your needs. Often, different situations call for one of the various methods.

Situation #1: When you want to specify your preferred domain

In this situation, you must use Google Search Console to state which canonical domain you prefer. This method is easy, fast, and works well for websites that have content living on one URL but with different domains. Here’s an example. Your local business may have an About page that also gets used on the regional website. Your URL for the page could be and regional website URL could be The problem with this method is that it only works for the Google search engine, no others. And, you must make sure the URL paths are identical. One cannot be “/about” if the other is “/about-us/.”

Situation #2: When using rel=”canonical”<link> tag

This is one of the most common ways to specify the canonical version of a page. When you use the rel=”canonical”<link>tag, you add metadata to the top of the page and specific the correct URL to be used for the canonical address. This tag is not added to the page’s header but added within the page’s head tags. It looks like this: <link rel=”canonical” href=”[canonical URL]”>. In this method, you don’t have to worry about URL paths like you do with the method above. It can be used for an unlimited number of pages. It also works with most CMS platforms which will set the canonical tags for you. The downside is that this method can increase your page’s size and thus slow down the loading times. Plus, if the CMS you use doesn’t automatically update your tags, you could fall behind on maintaining correct canonical tags.

Situation #3: When using rel=canonical HTTP header

Like the link used in the situation above, you can manually set a canonical link in the HTTP header response of your content. This method is often used when you have non-HTML content, like PDFs, on your website. You need to identify this content properly because the <link> tag metadata will only work on HTML pages. The benefits of this method? It can be used to map an unlimited number of pages without increasing the size of the page. However, it can be a more difficult method to implement correctly and challenging to maintain on large websites with changing URLs.

Situation #4: When you use 301 redirects

What is a 301 redirect? It is a permanent redirect that allows one URL to be forwarded to another. It tells Google that the page you’re being forwarded to is, in fact, the canonical version. You only really need to use this method if you’re phasing out one version of a page to use another version. Alternatively, if you’re forwarding the URL of a root domain to the URL of a subdomain. When you use this method in other situations, your sitemap’s clarity can be jeopardized.

The Power of Canonicalization

Every marketer wants Google and other search engines to find their page and show it to more users than the competition’s pages. Canonicalization is a super way to make sure search engines understand where your content is coming from. And, it tells them that your website is performing as strong as possible in the rankings. Canonicalization shows the structure of your content which proves just how unique your business is.

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