How to Apply Canonical Tags to Prevent Duplicate Content

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Bloggers work hard to rank high on search engines and consequently generate much traffic. Optimizing your content for SEO is one key to driving traffic to your blog.

SEO has several features, one of which is the canonical tag or “rel=canonical”. This tag identifies the master URL whenever there is more than one for a particular piece of content.

No matter how many versions of a piece of writing exist at different locations, the canonical tag tells search engines the one among them that is the primary or original source.

You can find this tag at the HTML top of your page. A canonical tag makes it possible to give credit to the original document and avoid the penalties associated with having multiple copies of a document.

Having duplicate copies of the content can create problems because of the way search engines are made to function.

Once the engine identifies the duplicate content of an article at different locations, the way it considers that article is affected. All of them become plagiarized to it.

Canonical is derived from its use in the Roman Catholic gospel that worked for several years and finally came up with four versions of a sacred account called the canonical books of the Gospel.

Canonical, therefore, means the genuine and recognized version of the content.

In the same way, whenever there are several and same versions of an online document, there is the need to canonize one in order for it to be recognized as the authentic version. The URL of the chosen document becomes indexed by Google as the original document.

When is it Important to Canonicalize Documents?

1. When there are URLs that show variations of the same product or content. This is when you are marketing a product with different specifications – for example if on your e-commerce site you have CK loafers that come in three colors (brown, black, and grey) and in different sizes too, and you have displayed each of them on a different URL.

If you have to rank such documents on search engine results pages, then you have to specify the canonical URL of the preferred webpage. This will prevent Google from identifying your products on the search engine as the same product being duplicated several times.

2. Sometimes, you create content having it on your mind that you want it to be displayed on both desktop and mobile devices and as such, you use mobile-specific URLs like a mobile-specific Subdomain or Accelerated Mobile Page (AMP) with the same content as the desktop URL, and then you decide which is the canonical URL.

You can browse Google to see how to differentiate between your AMP and your standard webpage.

3. Using URLs for different regions of countries. Sometimes, you may wish to geo-target in order to reach the right audience or increase your audience. You might have a product meant for some specific people in certain geographical locations like winter coats.

When marketing to two or three regions, you need to add a canonical tag if they are being marketed on different URLs but with the same written advertisement and in the same language. That way, the region-specific pages will all point back to the original page.

4. Self- referential URL is about creating a page and setting it as its own canonical. Having self-referenced tags are worth it because they optimize the performance of your web pages on search engines.

So, when you have content appearing on several URLs, the right thing to do is set the rel=canonical tag. This will help the search engine know which version of the content is canonical.

This will prevent any problem caused by duplication of content and will prevent your ranking on search engines from being affected. A canonical is like a 301 redirect, except that the canonical does not redirect.

Setting Canonical URLs

You only need to set canonical URLs when you have different pages that have the same content on it. The content must very closely resemble or should be the same. These versions must have been prepared and have links from some other sites.

For example, when you are promoting a service and you put it on different social media platforms, one of them needs to be uploaded to a search engine, and you need to show it, that is the copy to be uploaded to the engine. Here’s an illustration:


This shows that one post or product can have two or more URLs. But the content or products are on separate pages of your website.

Now, when you want to apply the canonical tag, you have to choose one of the pages – it may be the first that was created, the one you consider more relevant, or the one that has more links or visitors. Next, you add a canonical tag from the non-canonical page to the canonical page.

You can also change the canonical URL of some page types using SEO WordPress plugins.

Is it better to use canonical or 301 redirect?

As much as possible, you should use a 301 redirect. But where it is not possible, you use a canonical tag.

How do you set a canonical URL for your page?

There are several ways you can set canonical URLs for your page. Each way of setting it has its own advantages and disadvantages. And each one represents the same thing as the others. However, you should take note that canonical links are important for your pages.

Set it up with the Preferred Domain.

To set up the canonical URL, you need to check Google Search Console, so you can choose your preferred canonical domain. This is very helpful when you have the same content on different pages of your site having the same URL paths but different domains.

This is like having different Branches of the same company and a Main or Head office. All the offices are involved in the marketing of SUPER organic fertilizer. Now, each branch will have its own website and each website will have some pages that are the same as the others.

The product page is one of the pages. Now, the Head office will have the same description of the product on its website, so will the Branch offices too. One of them needs to be set as the canonical link.

However, you should note that as you set the preferred link on Google, the Google Search Console will reflect the change on Google Search Engine alone. You can decide that the Head office should be the one with the canonical tag.

To show which page is the canonical one,

  • Use the rel= “canonical” tag

This is adding more information to the page’s head tags to specify the URL chosen as the canonical link.

No matter the number of pages that have the same content, it is possible to specify their canonical link. Also, there are management systems that can set and update the canonical tags on your page’s metadata automatically. One of such is Hubspot.

The disadvantage of this method of setting the canonical page is that it can add to your page size and if your internet connectivity is not strong enough, it will affect how the pages load.

Also, if you have to manually update your website’s URL frequently, it will be difficult to maintain the right canonical tags.

Rel=Canonical HTTP Header

You can use this to put a canonical link on your HTTP header. You can use this method if you have non-HTML or PDF content on your website that you need to identify rightly. You can also use it when you have many pages.

However, it does not increase the bulkiness of the pages because they are not loaded as metadata. You have to be very careful when setting it up and it may not be the best method to use for large websites or websites that have their URLs changing frequently.

301 Redirects

You use a 301 redirect to forward one URL to another especially when it is not necessary to keep multiple versions of the content. For instance, typing redirects you to automatically.

The 301 redirect tells search engines that the URL to which a page is being forwarded should be the canonical link. This method works when you are forwarding the root to a subdomain.

Google, Yahoo, and Bing need URLs to know the pages that should be acknowledged as the primary source. You can use the canonical URL to reference a page for itself or to reference another page.

It can reference a page for itself if the content of that page is the only copy without any duplicate.

If you have an article that you did not index, it stands the risk of being duplicated and if you are unlucky, the duplicate copy can get indexed. That is why you should index your content whether there are one or several copies of it. For example:

Assuming this is the original copy which you did not index! These other duplicates of the same content came later. business/funds/

The first and original content which will not be indexed in any of the other duplicates gets indexed first.

Canonical tags are used to fix duplicate issues when there are query parameters used in the URL, or when there are multiple versions of a page or the pages show only a very slight difference.

Cross-Domain Canonical URLs

There are sites or blogs that take articles from other websites and publish on their sites because they want to meet the needs of their audience.

In this instance, the duplication of domains happens across different websites, which is different from when it happens across the pages of the same website.

In the event of such, it is important that a page has a canonical link in order to identify the original article and prevent it from being ranked low. A cross-domain canonical URL is used to index the source or original page.

If you observe the HTML of such articles, you will find a rel=canonical link that can show you the original version of the content.

URLs are necessary in order to safeguard your content. Take note of the following:

When you use the absolute URL, it gives complete clarity about the page that should be indexed. Look at this example

Look at the next one below. You will observe that it is not as complete as the example above. The one below will hardly prevent problems associated with duplicates.

One canonical URL should be set per page. Where it exceeds one, the search engine such as Google will only choose one and ignore the others. It is highly recommended to use just one URL per page.

Canonical URLs are to be placed at the section or HTTP header. If it is not placed there, it will be difficult for search engines to find and process it. This will, therefore, mean that all the copies of the content will be regarded as duplicates.

Using rel=canonical together with hreflang – In this case, the canonical of each language points to itself.

The Shortcoming of Canonical URL

As effective as canonical tags are in preventing duplicate content, it also has its shortcomings.

Where duplicate pages may have more links than the canonical links, these links are not fully passed on to the canonical page.

And since it is the canonical page that is indexed on search engines, these other links on the duplicate will be left out of the index. It is better to use a 301 redirect to pass on link authority.

Canonical URLs may let search engines know what to index but not what to crawl. If there are many redirect loops on a website, it might affect the ability of search engines to crawl through the site.


The canonical link is an important SEO tool that is used to prevent the duplication of content on search engines, which is capable of bringing down the ranking of a site.

There are many situations that bring about the duplication of content. You can use canonical tags to self-reference a page. This is to prevent it from being duplicated in the future with the duplicate page being ranked as the index page.

Canonical links are also to be placed in the

section; otherwise they will not be recognized or processed. So, each time you need to duplicate your content in order to boost your traffic or reach out to more people, take measures to ensure that they are recognized by search engines as the canonical link and duplicate link, so your rankings on the search engine results pages are not affected in any way.
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8 thoughts on “How to Apply Canonical Tags to Prevent Duplicate Content”

  1. yeah, this is very useful information that all bloggers should know. The fact that you get penalized for having duplicate content and all your pages end up being affected is heartbreaking. I have a question though if say I have a rugby website and I did a series on ‘how to pas’ and on each article, I duplicated the same 2 paragraphs on how to improve your pass even though everything is different, do I still have to apply Canonical Tags?

  2. This is a really interesting thing to read about, there are lots of times I come across same content on different websites and it gets really fuzzy to bear with those, it’s good that canonical tags can be added to make search engines determine which is the original, this will put people at safety of their contents and restrict it being used by someone else.

  3. Hello there, thanks a lot for sharing this wonderful piece of information here with us. I must say i really did enjoyed going through your article as it entails so much detailed and well explained information’s any online marketer especially the new ones would find useful. I think i will be sharing this with a couple of friends that really needs to see this. Thanks for sharing

    • You’re much welcome onboard, Philebur! Using canonical tags properly will save you from confusing search engine crawlers while in the process of indexing your site. Thanks for reaching out!

      Israel Olatunji

  4. This was an interesting blog that brought up a potential problem that I did not realize existed. This made me think about how I should be monitoring my content and URLs.  I have been applying my canonical tags for each of my posts or pages. I am confirming this as to not cause confusion for Google Search Console and Bing Webmaster Tools. This makes a good case to introduce the reader Wealthy Affiliate training. This provides the perfect opportunity of recruit members to WA

    • You’re highly cherished, Moonmount! Glad you found this post useful and engaging! Yes, canonicalizing your content will help search engine crawlers find and index your posts easily. Thanks for stopping by!

      Israel Olatunji

  5. Very informative and handy, i didn’t know about canonical tags till i came across your article. i haven’t come to the absolute or complete understanding of the subject but i am currently still reading about it. I definitely understand what they are used for as you made it very clear in the article and i am also glad that you clarified on the shortcomings as well. Thanks

    • Hey Chezya, thanks for leaving a thought! Yes, the use of canonical URLs will help search engine bots see your content as the original while any other URL bearing a similar post will be regarded as duplicate. So, it’s an essential SEO tool to explore if you want higher rankings on SERPs. Thanks for your message!

      Israel Olatunji


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