Canonical tags, otherwise known as rel=canonical, are used to guide search engines on specific URLs that indicate the main copy of a page. In other words, canonical tags tell the search engine crawler the version of a URL that a website owner prefers to appear on the search engine result page (SERPs). This might sound very trivial, but it's a major ingredient for SEO rankings

Canonical tags help to prevent problems that might be caused by duplicate or identical content that appears on different URLs.

Do Canonical Tags Really Matter?

Duplicate or similar content is a complex subject that affects SEO rankings. Now, you are probably thinking why would anyone even think of duplicating a page? Here is the point; search engine crawlers see every unique URL as a page.

For example; if your canonical URL is www.example.com/a, Google will understand that the other ones such as www.example.com/b and www.example.com/c are all duplicates.

This will tell the search engine crawlers that you want www.example.com/a to be assessed and indexed for ranking, ignoring the other URLs. I hope you got it now!

Canonical tags are also used for the cross-domain. For instance, if you decide to republish content on www.example.com/a to another website, simply add a cross canonical to tell Google that www.example.com/a is the original version.

Lots of SEO problems are caused when search engine crawlers go through different URLs that have identical or very similar content. This is because search engine crawlers might miss some of the unique content on your site.

Furthermore, large-scale duplication may decrease your SEO ranking potentials. And finally, search engine crawlers might select the wrong URL in place of the original, that's if your site content eventually ranks.

So, when you use canonical tags, it gives you full control of areas where you want the search crawlers to assess or avoid.