Let’s start simple – canonicalization is the process of nominating one single form of a webpage and having it load no matter what your visitors have actually typed in the URL.
Here’s an example – Google sees all the different versions of your site’s home page as different pages entirely – so if a visitor types www.xyz.com, Google thinks that’s different from just xyz.com; and it thinks that it is different from xyz.com/index; or www.xyz.com/index, or /index.php – and so on.
And another example that’s very relevant and very commonly NOT done properly – e-commerce sites. You’ve got ONE bag product that you want to appear on your website ashttp://www.shop.com/mybag.html
But that product has been categorised in your e-commerce system as a handbag – so it can also be found using your system as http://www.shop.com/handbag/mybag.html
Oh and it’s also classed as an oversized handbag – so it appears also if you type in –http://www.shop.com/handbag/oversized/mybag.html
According to you, and to the visitors for your site, the above are pretty much the same product and look like the same webpage. In order for SEO to work properly, though, they should be the exact page. You need to make sure that whateverversion of your URL your site visitors are typing in; they are still getting through to the same, canonical page. That is what Google calls it – canonicalization of your content and pages.
Canonicalization of a URL is important for the SEO of your site. Google actually supports a canonical tag, which helps. The tag is applied to all the versions of your webpage that are not canonical. It tells Google that the page it has returned is one of the alternate versions, and that it should apply its metrics to a different page in lieu of the one it has found – that is your nominated canonical home page.
Why is this important? Because when you have different versions of the same page loading under all those different URLs then Google can think you have duplicated a load of content and penalise you for it. By making one address canonical, you are showing Google that there are copies of your home page out there that have been designed simply to give users access to the right content no matter what they type into the URL.
