What is Canonical Tag and it’s SEO Benefits

Canonical Tag SEO

Since early 2009, the major search engine firms (Google, Bing, Yahoo, etc) has been utilizing canonical tag to improve the quality of results in SERP’s.

Despite the benefits, it offers most of the webmasters are not implementing it due to a lack of knowledge regarding the canonical tags and its purpose in SEO.

In this article, you will be understanding what is Canonicalization and the benefits of canonical tag in SEO ranking factors.

Introduction to Canonical Tags?

A canonical tag is represented as rel=”canonical’ in HTML and it is a way of telling search engines that a specific web page URL represents authenticity of a given web page.

Website penalization for self-plagiarism or duplicate content appearing on multiple web pages can be prevented with the help of canonical tag.

Canonical tag instructs search engine which version of a URL it must use to index and rank in search results.

Canonical Tag Syntax

The canonical tag should be implemented in the HTML header part of your webpage, where you would find title and meta description tag.

From an SEO perspective, the canonical tag is similar to the 301 redirection property. Instead of redirecting audience to the main URL, you’re instructing search engines that multiple version of URL should be considered as one web page.

Benefits of Canonical Tag in SEO

When search engines crawl duplicate content (many URLs with very similar content), then it will affect your website ranking in SERP.

Many website owners have faced issues with different URLs having identical content. This scenario creates three big problems for the search engine:

  • Firstly, the Search engine doesn’t know which version of URL to index in its database.
  • Secondly, Search engines don’t know whether to direct the page rank score to one page or keep it separated between multiple versions.
  • Thirdly, Search engines don’t know which version of URL to rank in result pages.

When these kinds of scenarios arise, webmasters started implementing the new canonical tag which will help us to control the duplicate content on our website.

Why Canonical Tag is Important?

You might be wondering why would anyone create a web page with duplicate content and many people assume that canonicalization isn’t something they need to worry about in the SEO ranking signals.

The problem with humans is that they tend to think of a web page as a concept but for search engines every version of URL is a separate new page.

For example, a search engine might be able to reach your website with all the following version of the URL mentioned below:

  • http://www.domainname.com
  • https://www.domainname.com
  • http://domainname.com
  • http://domainname.com/index.php
  • http://domainname.com/index.php?ras%2hsa…
  • http://domainname.com/amp

In the above example, you can see there are six versions of the homepage URL. In reality, you may encounter a large chunk of URL versions which might be created manually or generated automatically through software bug in the website.

To an individual person, all of these version of URLs represent a single web page. Although, search engine crawler treat every single one of these URLs is a unique web page.

When this happens website suffers ranking and traffic losses and the relevancy of the web page will be lowered.

To overcome these losses, website owners made use of canonical tag which will notify search engine the most relevant page to display in search results.

SEO Implementation of the Canonical Tag

Issues with self-plagiarized content can be extremely tricky but here are some of the important things to consider when implementing the canonical tag on your website:

Self Referential the Canonical Tag

It’s all right to point the original content URL in the canonical tag. For example, if you have 3 version of URL as X, Y & Z, and X is the canonical version. It is fine to add X URL link in canonical tag pointing on web page X. Self-referring canonical tags is a best SEO techniques which improves the relevance of the web pages.

Home Page Canonicalization

Duplication of home page URLs is very common, where people will link to your homepage in many different ways which you can’t stop from happening. It is always a good thing to add a canonical tag on your homepage layout to prevent unnecessary problems.


Analysis of Dynamic Canonical Tags

Due to bad coding structure sometimes a site may generate a unique canonical tag for every version of the URLs (each version of URL will have its own canonical link). Detailed examination of the URLs is very important especially on CMS-driven and e-commerce websites.

Avoid Blend Signals

Search engines will not consider canonical tag when you send irrelevant or incorrect signals. For example, when you canonicalize page A to page B and then page B to page A. Also, when you canonicalize page A to page B and then redirect page B to page A. Likewise, chain canonical tag (A to B, B to C, C to D) is not a good SEO practice. Always send clear signals to search engine so that crawlers can easily perceive your website structure.

Prevent Canonicalizing Mishap

When people encounter web pages with similar content they think of canonicalization. You need to proceed with caution while implementing the canonical tag on the website. In general, it is fine to use canonical tag for identical pages such as a product page that differs attributes of currency, location, or quantity. It is important to be aware that the non-canonical versions of the web page will not be processed in search results and the search engine will ignore the canonical tag if the pages are too different or not relevant.

Domain Canonicalization

Canonical tag can also be implemented across multiple domains. Let us assume you’ve authorized access to publish the same article across multiple sites. With the help of a canonical tag, you can improve ranking power on just one site. You need to make sure the domain matches your business niche and also keep in mind it will prevent the non-canonical sites from ranking in search results.

Strategies for Canonicalize Multiple URLs

There are many ways to canonicalize multiple URLs having similar and identical content on your website.


Canonical tags aren’t the only way to manage multiple URLs. But it is one of the most recommended and safest ways to manage duplicate content on your website. There are various ways available for canonicalization and sometimes we may have to apply these strategies if the situation demands.

301 Redirection

The 301 redirection is basically a status code telling Search Engine, ” I’m going to take my webpage X and I’m going to point it to webpage Y.” When you don’t want anyone to visit webpage X and don’t want it clogging up the web analytics. You can implement a 301 redirect strategy when you want to pass the link juice of the old URL to the new one.

URL Parameters in Webmaster Tool

When you have very complex websites with tons of URL parameters and sometimes it can be just an incredible pain to clean up all these URL parameters. In these kinds of scenario you to add the canonical tag to all these different kinds of pages in a very short term. Log in to your webmaster tool account and go to the URL Parameters section. Here you can submit URL syntax and you can set it to be passive on all types of URLs. This way search engine treats those URL parameters like it doesn’t exist at all and it will be a helpful way to canonicalize large cluster of URLs.

Fragmenting URL

You can use the location hashes in the URL when you have pages with the same content but with one slight difference. Fragment URL is where your audience will jump to the different section on content in the webpage. Search Engine considers all hash URLs as one URL. So they are not going to rank them differently in search results and also they don’t get indexed differently. Fragmenting URL essentially canonicalized to the same URL.

Canonicalization Strategies to Avoid

Blocking Other Version of URLs from Crawling

When you allow one URL and block search engine spider from crawling other versions of URL with robots.txt then a search engine will not know they exist. The traffic, backlinks, page authority and ranking signals carried by the different versions of URL will not be transferred to any web pages and that’s something you do want to go waste.

Blocking Indexation

So you might say that by using the meta robots no index tag, the search engine can see the webpage but will not index the different version of URLs. Here also the same effect will take place where you prevent the link juice of different versions of URLs from being transferred to the main indexed URL. Combining the ranking signals of multiple pages and creating a single energetic URL is something you really want.

Using 30X Redirect Signal

It is not recommended to use 302, 307, 308 or any other redirection expect 301. Search engine often treats 30xs redirect similarly, so 301s redirection is probably better for canonicalization of URLs with similar content.

40x the Other Version of URL

Don’t 404 web pages when you could 301 or use rel=canonical inside the header section so that you take all the advantage of ranking signals. You lose the existing authority and link juice of web page when 404 signal is triggered by the search engine bots. It’s better to pass the 40x signal only when the page is very new, when you’ve got an error or when you think it doesn’t have ranking signals which can be beneficial.

Best Practices of Canonical Tag in SEO

For an SEO professional, it is important to know when to implement the Canonical Tags on the website. Let’s look into the scenarios where the canonical tags will benefit the ranking factors in SEO.

  1. You can always blend links with the canonical tag when the content is exactly duplicated on multiple version of URLs.
  2. You can collapse link with canonical when two different URL serve the purpose even if the targeted keywords somewhat vary. When the content is not extremely similar but the meaning of phrases and sentences structure is the same.
  3. When you’re republishing or updating the old content as a new article/link and you want to maintain the old version then canonicalization will be a better option to proceed.
  4. When existing content is no longer useful and the better version of the content is available which be identical to old content such a product page or event link.

How to Inspect Canonical Tags for SEO

When you’re auditing the canonical tags of a webpage, there are a number of things that need to inspect for better performance in SERPs.

Here are very common things should be audited when you implement canonical tag:

  • Check whether the page has a canonical tag?
  • Check whether the link in the canonical tag point to the right page?
  • Check whether the pages are crawlable and indexable?

A common error people make is when they implant the link in a canonical tag that is either blocked by robots.txt or is set to noindex.  This can send confusing signals to search engines and will affect the page ranking in a search result.

The simple way to inspect and audit your canonical tags is to examine the source code of the webpage.

Let me explain with a practical example:

I have two different versions of URLs which have duplicate content and I have blended both the version of URL with the canonical tag for better page rank.

Canonical Tag 1

  • Version 2: The AMP (Accelerated Mobile Pages) version which will be utilized in mobile search results.

Canonical Tag 2

The canonical tag has been implemented in the header section of AMP version URL and canonicalized the article link as original content which will be indexed and ranked in search results.

To examine the canonical tag, you should check the source code of the page by pressing “CTRL+U” or right-click and select source code.

Canonical SEO

In the source code, search for canonical tag “CTRL+F” in the <head> section and inspect whether the URL in the canonical tag is pointing to the right page.

Wrapping Up

Although a penalization for plagiarized content is unlikely but indexing all of your self-plagiarized content will affect the relevancy of the website and could also cause the problem in the search result ranking.

However, canonical tags are the safest way out is these circumstances and will automatically improve your sites visibility and overall SERP ranking.

If you have implemented canonical tag on your website then do let me know in the below comment section how your site is performing in the search results..?

More Resources:

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