Canonicalization – How is it important for SEO
What is a Canonical tag?
A new HTML element was introduced a decade ago to link the original URL of a webpage for a search engine. This element is the canonical tag of an URL. Interestingly, the word canonical traces back to biblical history where it loosely translates to being accurate! This canonical tag points the search engines to the one copy of the webpage (which can be the master copy) you want to be displayed in the search results. Hence it is important to add this tag to that one page you want to be displayed as the original or genuine. This will solve the problem of having duplicate pages that have similar or same content and thus give best SEO search results.
Why should you add a Canonical tag?
The concept of canonicalization can be better understood with an example. Consider a website that can be reached by different ways through a search engine:
www.xyzexample.com
http://www.xyzexample.com
https://www.xyzexample.com
http://www.xyzexample.com/index.php
Note that, all the above URLs will take you to the same page of the website. For a reader, all these URLs mean the same that will direct to the Home page of the website. But for a search engine, every URL is different and leads to a different page. By adding a canonical tag, the search engines will list all the URLs under one index, thus increasing the search ranking or points.
How to add a Canonical tag?
Now that we have understood the importance of adding a canonical tag, lets see how to add it. Let us refer to our previous examples of the URL links.
Suppose the URL link
http://www.xyzexample.com/index.php has the same contents as that of the URL link
https://www.xyzexample.com.
If we want the second URL link to be the canonical URL link, then a canonical tag has to be added in the first URL HTML to link it to the second URL link. This single line of HTML code will add a canonical tag.
In the <head> section of the first URL link, insert this tag:
<link rel=”canonical” href=”https://www.xyzexample.com” />
This will merge both the URL links as one for the search engine to index and redirect the reader. Similarly, canonical tag to one canonical URL link can be inserted in all the different pages, that you think has the same or similar content.
Which pages should have Canonical tags?
The canonical tag assures that the genuine page is reached by the search engine. Hence, there should be a rel=”canonical” link from every non-canonical page to the canonical one. Does that also mean that there has to be a canonical tag to its own page? It has been found that Google recommends to add canonical tag to every page of the website, even though it is to its own page. This will help eliminate the duplicate content. Also, various content management systems allow multiple URL paths to reach a webpage; which will make the search engines to identify them as separate pages with duplicate content. By adding a canonical tag, this confusion can be avoided. It is also recommended to canonicalize the homepage of your website, as it can be reached by different URL links through the CMSs or social media platforms.
What precautions to follow when applying Canonical tags?
As much as the canonical tags are important, there needs to be precautions exercised to achieve the purpose of adding canonical tags. Some of them has been listed below.
Check for different canonical tags
Sometimes different canonical tags get added to every version of the URL links, entirely missing the purpose of canonical tags. This should be avoided by frequently checking the tags specially on CMS-driven sites. The results of this practice are unpredictable.
Use complete canonical tags
There are cases when the shorter, page related links are added for canonical tags. For example, do not add a link that is:<link rel=”canonical” href=”index.php”>.This is not considered as the best practice.
Keep away from mixed up canonical tags
When you canonicalize page 1 to page 2 and then page 2 to page 1, the search engine will ignore the canonical tags and give unpredictable results. Hence, avoid canonicalization of paginated links.
Misplaced canonical tags
For a canonical tag to work correctly it has to be placed between the <head> and </head> section of the HTML code. The canonical tags outside of the <head> section will be completely ignored by the search engines.
Using canonical tags for similar content
It is okay to use canonical tags to link two different websites until they have similar or the same content. For example, an e-commerce website that sells same products in different regions with only the difference in say currency or quantity. Until the description of the product is same, there could be a canonical tag added to link to one of the websites. But, this could prevent the non-canonical versions of the pages from being ranked.
Cross-domain canonicalization
Let’s say there is an educational institution running many schools. They have similar content that will be published on all their different school websites. Here a canonical tag can be used to enhance the ranking of just one of their school website, maybe the most popular school they run. But the non-canonical sites will be prevented from ranking.
Canonical tags and 301 redirects
A 301 redirect and canonical tags may appear similar but using them will give you two different results. When a 301 redirect is used for Page 1 to Page 2, then the reader is directed towards Page 2 without being aware of Page 1. But in canonicalization of Page 1 to Page 2, the search engine knows that Page 2 is canonical, and the reader is aware of the existence of Page 1 also.
Conclusion
A canonical tag when used wisely with caution can give very good SEO results. Canonicalization is an important process that could bring significant SEO improvements for bigger websites.