An Absolute Beginner’s Guide to URL Canonicalization and How it can Improve your SEO

Do you want your website to be ranked better by search engines?

Of course, you do.

Unfortunately, there is no cheat sheet that you can follow to increase your website’s ranking.

However, search engines like Google have publicly declared several technical aspects that they use to rank webpages, one of which is URL Canonicalization.

 Formal definition of Canonicalization

In mathematics and computer sciences, Canonicalization refers to the process of converting an object having multiple representations into a standard, regular or canonical form, allowing it to be uniquely identified.

What is URL Canonicalization?

In web search and SEO, canonicalization has a slightly different interpretation.

URL canonicalization has been around since 2009 and tells Google to choose the preferred URL between two similar URLs. This can perhaps be best illustrated with an example.

Consider these URLs of the same website –

• http://www.example.com
• http://example.com
• www.example.com/index.html
• example.com/home.asp

For most humans, these URLs will mean the same.

However, technically, all these URLs are different and could show completely different content.

By ‘canonicalizing’ a URL, we instruct the search engine to treat our chosen URL as the best representative from the set.

When to use canonical tags?

When Google is presented with two similar URLs (and) or pages having almost similar content, a canonical tag specifies the original content page to the search engine.

URL canonicalization is also a solution for duplicate content issues.

Why canonical tags are beneficial for SEO?

Duplicate content incurs heavy penalties from search engines and causes several problems.

Firstly, search crawlers will spend a considerable amount of time crawling through duplicate content and may end up missing unique content.

Secondly and most importantly, having too much duplicate content can be detrimental for your ranking metrics.

The search engine is then in a fix about which version of the page to index, which to rank for relevant queries and whether to consolidate ‘link equity’ on a single page or split it between all the versions.

Ultimately, the search engine bots will label one of the sites as a copy of the other and penalize it.

This is especially concerning for modern content management systems (CMS) like Drupal and WordPress, eCommerce websites and dynamic code-driven websites, which allow the users to access the same content through multiple URLs and adds URL parameters for searches, sorts, language options etc.

The website can then have thousands of duplicate URLs, which becomes a major SEO vulnerability.

By properly implementing canonical tags, these pitfalls can be avoided, which results in robust sites that conform to SEO best practices and organically rank higher.

How to correctly implement a canonical tag?

Canonical tags are included in the section of a webpage and have the following syntax –

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

Here link rel = “canonical” denotes that the link in the tag is the canonical version, and href = “https://example.com/sample-page/” gives the URL where the canonical version can be found.

Common considerations for implementing canonicalization

Some of the important things to consider while implementing URL canonicalization are:

1.  URLs can have canonical tags pointing to themselves. Self-referencing can ensure that the search engine recognizes your site as the original copy.

2.  It is a good idea to put a canonical tag on the homepage of the website as homepage duplicates are common and people can link to the homepage in many ways

3.  Canonical tags should not be chained together (A -> B, B -> C, C -> D)

4.  Canonical tags can be used across domains. This can allow ranking power to be focussed on a single site.

5.  The rel = ‘canonical’ should only appear in the section of the document. A canonical tag placed anywhere else can cause it to be ignored

6.  Multiple canonical tags in a website will cause it to be completely ignored by the search crawlers.

7.  The canonical markup should be as complete as possible. For example, instead of the canonical tag

thewebpage.org is a better way to apply canonicalization

 

8.  Paginated pages should all use self-referencing canonicals instead of being canonicalized to the first page of the series

9.  A canonical URL should not point to a website which has a non-200 status code. A website with a 301 or 302 status code will force the search engine crawler to crawl an extra page, which depletes the crawl budget. A website with a 404 status code is a complete waste for the crawler and the search engine will ignore the tag

10. The canonicalized URL should not be blocked via robots.txt as it prevents the search engine to transfer any link equity from the non-canonical to the canonical.