What You Need to Know About Canonical Tags in SEO

Canonical tags are an important part of search engine optimization or SEO. To create a holistic SEO strategy for your business, you must know how to use canonicalization and implement canonical URLs for your website.

If you implement such tags incorrectly or inefficiently, you may end up losing traffic or search rankings due to duplication issues. Needless to say, Google gives great importance to canonical tags, which decides your site performance in terms of search rankings. This is why you must use canonical tags and URLs properly.

However, for proper usage, you should first know what canonical tags are, how they work, and how you can add them to your website. 

What are canonical tags and canonical URLs?

Canonical tags were started in 2009 by Google, Microsoft, and Yahoo together, to find a way to get rid of duplicate content issues. A canonical tag, also known as “rel canonical” is a tag placed on a page’s source code.

It indicates to search engines that there is a master copy of that page. In SEO, canonical tags help search engines index the correct URL so that duplication issues can be resolved. 

Basically, the canonical tag is an HTML specification appearing in the header region of the website’s source code. If correctly indicated, search engines will know to index only that source and consider other similar ones as duplicate. 

This HTML code snippet defines the main version for similar, duplicate, or semi-duplicate web pages. For instance, if there is similar content under different URLs, canonical tags will specify which page is the main version and thus should be indexed.

What You Need to Know About Canonical Tags in SEO

In case your website has identical or somewhat similar content under multiple URLs, you can choose which one to mark as the main source. This way, the search engine will know which URL to feature in SERPs. This practice helps in unifying website traffic and consolidating link popularity to your preferred page.

Any search engine can recognize canonical tags while crawling and indexing websites. 

How can canonical tags be specified?

Canonical tags have a consistent syntax for specification. They are placed in the header area of the web page. For example:

You may also like: Most Common Errors Found in Programing & How to Avoid Them

<link rel=“canonical” href=“https://custardpie.com/recipe-page/” />

In this code,

  • link rel=”canonical” indicates that this is the master version of the web page and should be considered the main source for similar content.
  • href=“https://custardpie.com/recipe-page/indicates that the canonical version of the web page can be found in this URL.

Let us look at another example. Suppose your website has two URLs with almost similar content.

The first one is the standard resource and the second one is a sub-category of the first. In this case, the first URL is the more important one and should be indexed by Google. Hence, you should place the canonical tag in the metadata of the first URL, as follows.

<link rel=”canonical” href=”https://www.scenario.com/fantasyesamples.htm”> />

Now, search engines will consider this version of the page to be ranked for SERPs.

Why are canonical tags important for SEO?

As said earlier, canonical tags help distinguish between duplicate content. They tell the search engine that there is a standard resource for multiple similar pages. This specification is important as Google does not like duplicate content.

Having significant duplication in content also affects the crawl budget, which means Google will waste time crawling multiple versions of the same web page instead of moving on to other content on your website. 

While coming across multiple URLs with similar content, Google is confused about which page version to index and rank for search queries. There is also confusion regarding link equity, whether it should be consolidated to one page or divided among multiple versions. Thus, duplicate web pages have a negative effect on SEO. 

What You Need to Know About Canonical Tags in SEO

Canonical tags help to solve all these issues and boost SEO. Some of its benefits are as follows.

You may also like: Unlock The Future of Business: All-in-One Discrete ERP Software

Specifying the Search URL

Adding a canonical tag ensures search engines know which URL to consider for search results. Thus, when a user searches for the featured keyword, the web page of your choice will pop up in the SERP. 

Failure to specify a canonical URL leads Google to make its own choice about which link to index. This is not always wise as you may end up getting featured for irrelevant content, which will again reduce your SEO effectiveness.

Enforcing Link Signals for Identical Pages

If you are looking for external links to boost your search rankings, canonical URLs are a must. If you have multiple duplicate pages, the earned links from external sources may end up getting divided among the URLs.

A canonical tag helps consolidate the link signals from other pages into the specified URL. This way, your site will rank higher as distributed links will be consolidated into one page.

Guiding Google to the Right Page

This is the most obvious benefit of using a canonical tag, as mentioned earlier. After all, the end goal of SEO is to get your website featured in SERPs and boost search rankings. Instead of spreading the crawl budget over multiple pages, canonical tags direct Google to the page of your choice for more relevant search results.

Best Practices to Implement Canonical Tags

You already know how to use “rel=canonical” to implement canonical tags. Now, we will mention some best practices for implementing these tags.

  • Use lowercase URLs as Google may end up treating uppercase and lowercase URLs as two different versions. For that, make sure all URLs on your server follow the lowercase format.
  • Pay heed to the SSL factor. For instance, getting the Secure Sockets Layer certificate for your website changes its domain version from HTTP to HTTPS. Ensure you declare the right version in your canonical tag.
  • Each page should have only one canonical tag. If you have multiple, Google will ignore all of them and the whole exercise would be futile.

Canonical Tag Signals

There are certain canonical tag signals that should be used.

  1. HTML tag (rel=canonical): This is the simplest and most popular way to declare a canonical tag.
  2. HTTP header: Instead of putting the canonical tag in the page header, you can put it in the HTTP header as well, especially for documents like PDFs.
  3. Sitemap: Non-canonical pages are not supposed to be included in sitemaps, so you can list those pages in your sitemap that you want to make canonical.
  4. 301 redirect: 301 redirects can be used to divert traffic from duplicate URLs to the canonical page. 
  5. Internal links: if you link your internal web pages to a specific page, it can be considered canonical. Hence, make sure your internal link signals are consistent.
What You Need to Know About Canonical Tags in SEO


Canonical tags have specific norms to be implemented but if done correctly, they help reduce content duplication issues to a great extent. However, you must note that canonical tags are hints and not directives. Google may choose to ignore it in certain cases. To reduce chances of that, you can opt for expert SEO services. This can help you use canonical tags effectively and get the best results for your website.