What is rel=canonical?
In a nutshell, rel=canonical is a way to clean up duplicate URLs on a website. I know what you’re thinking, it would be much easier if duplicate content just didn’t exist at all. This would make my job all sunshine, rainbows and flowers rather than the sweat and tears it generally involves, but this is the real world and duplicate content is sometimes unavoidable.
This is especially true when it comes to ecommerce sites which pose some of the most complex mysteries for SEO forces all across the nation. The way that many of these sites present information or products to users means that some pretty wacky things can happen to the URL – all designed to provide the most relevant results to users through the use of parameters.
Read more: 7 Things To Remember About Rel=Canonical