What is canonicalization?
Canonicalization is a technique that aims to address duplicate content issues by specifying which URL of a page should be shown in search engine results.
Why is canonicalization important?
Websites sometimes cannot avoid creating duplicate content. For instance, some websites have separate servers for desktop and mobile traffic. Hence, they need to duplicate their content on both servers so that all users can access it. Take these two URLS as an example:
- https://www.helloworld.com/sample-blog/ – Desktop Version
- https://m.helloword.com/sample-blog/ – Mobile Version
In the eyes of a human, both web pages are the same because they have the same content and come from the same company. However, in the eyes of a web crawler, they are different because they come from different URLs.
Canonicalization allows you to specify which of the duplicates will be indexed by search engine crawlers and be served to search results pages.
How can we specify canonical web pages?
One way of specifying which content is a “canonical” webpage is through the use of canonical tags. A canonical tag, also known as rel canonical, is a type of HTML code that enables web crawlers to identify the canonical URL of a specific webpage. This way, duplicates can point to the original web page content and web crawlers will only index the original. Here is an example of a canonical tag:
<link rel=”canonical” href=”https://www.helloworld.com/sample-blog/” />
Notice that the href part of the code is the canonical URL. It’s basically telling the search engine crawler to use and index content in “https://www.helloworld.com/sample-blog”, which is the Desktop version of the sample URLs above because this is the original content of the duplicates.
What are the benefits of specifying canonical URLs?
- It allows web crawlers to efficiently index your website. Web crawlers have a limited amount of time crawling your website. This amount of time is called the Crawl Budget. By specifying a canonical URL for your duplicate pages, then web crawlers will spend less time on your duplicated content and focus more on indexing your unique ones.
- It strengthens the rankings of our webpage. Without canonical tags, your duplicate pages may compete with each other in search results pages. Moreover, seeing duplicate content in search results is not a good user experience, which may increase your bounce rate.
Canonicalization – Moz