How to Use Canonical Tags for Better SEO

Resolving and preventing duplicate content issues are key to improving your search rankings. Canonicalization is one of the solutions you can use immediately.

With a canonical tag, a webmaster is able to optimize a website easily in favor of presenting the preferred version of a piece of content – which inevitably allows for better indexing by search crawlers.

What is canonicalization in SEO?

The definition of canonicalization is the process of using a canonical tag to specify the preferred URL for a web page to show visitors, where several copies or choices of the same web page exist. Through this process, search engines are able to determine that links to different versions of a single content should act as links supporting the selected canonical version, thus improving the content’s performance in the SERPs.

A canonical tag example looks something like this:

<link rel=”canonical” href=””>

What is the difference between a 301 redirect and a canonical tag?

A 301 redirect is only used for a web page that has been moved to a new URL permanently. This will transfer any link juice powering the old URL to the new URL and also tell search engines to index the newly redirected URL instead.

A canonical tag is used in scenarios where multiple pages of the same content exist on the internet and you want search engines to know that the other versions are meant to supplement the canonical version. This in turn gives credit to the original content – not the non-canonical pages.

Why use canonical tags?

Not specifying a canonical tag for identical content will lead search engines to decide on their own which piece of content to index on their own, which may or may not be the best version of your content there is.

There may be scenarios where you have similar content spread across your website which may penalize your rankings if not optimized properly. Canonical tags will serve to sort duplicate content issues out and point crawlers in the right direction for ranking purposes.

When should you use the canonical tag?

Here are some common scenarios where canonical tags are used for SEO:

    • Session IDs

      With multiple URLs being generated for individual user session IDs, page duplication problems will arise due to the same web page being created repeatedly for each new user visiting your site. Using a canonical tag to point each session ID to the right version of a web page will give search engines the proper information in indexing.

      When you have 10 users logged into your e-commerce site at one time, and 10 URLs of the same product page are generated due to individual session IDs, you want those tags in place to prevent duplicate content penalization.

  • Subdomains

    Different subdomains of a single website are seen as different websites in search engines, and search crawlers will index them accordingly. To prevent this divide, you need domain canonicalization. Add canonical tags to point subdomains to the main domain for search engines to index correctly.


For example: your domain is and you have two subdomains and You can use canonical tags within those subdomains to specify that is the main domain for indexing, and that any link juice granted to these subdomains should support the main domain only.

  • Separate mobile websites
    Creating a separate mobile-friendly version of your website (e.g to provide targeted content to your users on mobile platforms could work well in your SEO strategy. With Google’s ‘Mobilegeddon’ release on April 2015, mobile-friendly websites now rank higher in mobile results instead of sites designed for desktops only.


To make sure your website does not get penalized due to duplicate content, you will need to use canonical tags to let search engines know that the content featured on both mobile and desktop are similar.

  • Blog Categories
    A single blog post can sometimes be segmented into more than one category, and in which case multiple URLs might be generated for the same piece of content to accommodate the different categories selected.


Using canonical tags in a scenario like that will help ‘explain’ to search crawlers that category URLs generated all point back to the same page, which will also help with directing any backlinks to the original content.

How do you implement a canonical tag?

To start adding canonical tags to your web pages, you should:

  1. Identify which URL is the canonical version that you want your other non-canonical URLs to link to.
  2. Input “insert canonical URL” /> in the section of your selected canonical page. By inserting the canonical tag into the canonical page itself, it tells search engines that this is the canonical page to index.
  3. Input “insert canonical URL” /> to the section of the other non-canonical versions to point search crawlers to the preferred canonical URL of your content.

Every optimization step taken goes a long way in your SEO. Use canonical tags and get those duplicate content issues sorted for better ranking in search results.