What is a Canonical Tag?

Mackenzie Griffith

  | Published on  

May 26, 2021

Do you have multiple copies of one page? Want to avoid multiple duplicates of one URL? Canonical tags have been around since 2009. They were founded by Google, Yahoo, and Microsoft. Canonical Tags were made to do just this, avoid duplicate issues. It's a simple tool that goes a long way.

What are canonical tags?

A canonical tag is a portion of HTML code that determines the main version of the duplicated pages. To put in simpler terms, if you have the same content under multiple URLs, canonical tags decide which one of those versions is the main one.

If you are still unsure what we mean by canonical tags, here is an example: <link rel="canonical" href="https://www.website.com/page/" />

Canonical tags help Google to determine which version of the URL you want to appear in search results. It is important to note that canonical tags and URLs are often used interchangeably but there are important differences between these terms. URLs are a more general term to indicate any link that you would share with another person or search for online. However, canonical tags are a specific form of URL to indicate to a search engine which is the master copy of a page and which has the duplicate content.

Overall, canonical tags are used to tell search engines what is original content and what should be indexed and displayed on the SERP.

What does a canonical tag look like?

Canonical tags are placed within the head section of the webpage. There are a few ways you can index the canonical page among the duplicates.

  1. You can add <link> tag in the code of all of the duplicate pages that points to the canonical page. The code looks like this: rel=canonical <link> tag
  2. You can create a new URL with the canonical version: href="https://example.com/sample-page/

For more information on what canonical tags may look like click here.

Why are canonical tags important for SEO?

Having multiple duplicates makes it harder for Google to choose which of the versions to index and rank and when to consolidate link juice. Google does not like duplicates!

Having multiple duplicates can also affect your crawl space. Google ends up wasting time crawling the multiple duplicated pages instead of finding the important content on your site. When Google spends time crawling new pages on your website, rather than duplicate content, it can make your website rank faster. Therefore, using Canonical Tags is very important!

You would also use a canonical tag in SEO because when you have near-identical pages on your website, individual URLs could link back to your website from external sources. Creating a canonical tag allows you to have control to consolidate these external sources into one URL that you specify. While your customer will get some information on the duplicate content's page, there is always the chance there is a vital part of your business that they are missing when they end up on a page of duplicate content rather than the master page.

Here are some things to consider when using canonical tags

Always double check your code

Bad codes can cause your site to write a different canonical tag for each URL, which can completely disrupt your reason for using a canonical tag. So, make sure to double check that your codes are correct!

Put a canonical tag on your homepage

Homepage duplicates are very common, and people my link you homepage for for various reasons, so it is always a good idea to use a canonical tag here. Having a canonical tag on your homepage may prevent problems from occurring down the road.

Canonical Tags vs. 301 redirects

We have discussed what 301 redirects are before at Centori. Because of that knowledge, you may be wondering when it would be best to use a canonical tag as opposed to a 301 redirect. While both canonical tags and 301 redirects tell search engines to treat multiple pages as a single page, a 301 redirect redirects all traffic to a specific URL while a canonical tag does not. Canonical tags therefore are best thought of as helpful for search engines when they crawl your website while 301 redirects are used for your website viewers who are looking for information on your website.

As a basic rule of thumb, remember that if your website structure has changed, 301 redirects are the best method to use. If your website has duplicate content and you want to measure traffic to each link, use a canonical tag.

How to optimize SEO through canonical tags

When using canonical tags, there are a number of ways to optimize SEO. Here are some ideas to consider:

  • Does the page have a canonical tag?
  • Are the pages indexable and crawlable?
  • Does the canonical tag point to the right page?

One mistake that can feed the search engine confusing signals is pointing the canonical tags to a URL that is set to "noindex" or blocked by robots.txt, so pay attention to this in your settings.


Canonical tags are essentially the cleanup of your website. They indicate the main version of the duplicated URL's so that Google can index and crawl your page smoothly. Canonical tags are essential to use when building your webpage, as they help to avoid unforeseen problems in the future. Duplicated content is a complicated problem, but canonical tags are just the way to fix this!

So if you are a business owner looking to cleanup your website, consider using canonical tags. They make you life easier and your website run smoother!

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