I am currently building up a glossary of terms for the Blueclaw site which I hope to put live soon and was inspired to write a post on canonicalization. Unfortunately I am still trying to come up with a good definition for it so I will stick with the definition of Matt Cutts:

“the process of picking the best URL when there are several choices…”

In web design there can be a multitude of URLs being directed toward the same page. This is most commonly an occurrence with the homepage of a site. For example you have two URLs http://www.examplesite.com and http://examplesite.com both take the visitor to the same page (being the homepage) however they are different URLs. On top of this there may be other variations such as http://www.examplesite.com/index.php and even further on than this you may own different variations of the domain like http://www.examplesite.co.uk . So if you think about it there are already potentially 8 different URLs for your site and all for the same page.

Now this has quite big implications for SEO. Firstly one of the main problems with this is that it can confuse the search bots. Which of the URLs are they supposed to index?

However one of the major problems with canonicalization comes down to link building. If a page has 8 different URLs pointing to it than that means that there are 8 ways in which other sites can link to yours which can greatly dilute the amount of link juice your site could potentially receive.

So before an SEO campaign starts ensure that this is not a problem. Now there are two ways of doing this. the first one is quite a recent development and this is using a canonical tag. If you want to read more on this then it have a read of Vanessa Fox’s post on Searchengineland but in a nutshell the canonical tag works by putting the tag in the head section of the page and specify the canonical version of your page like so:

This tag tells the search engines that they should index the canonical URL specified in the tag. The only problem with this tag is that users can still use the different URLs and for this reason we still recommend 301 re-directs to the canonical URL. Although a bit harder to implement 301 re-directs it is definitely more worthwhile. It means that only the correct URL will be displayed when a user visits your site and it also ensures that link juice is passed through to the correct URL from any links directed through to any of the URL variations. For more information on 301 re-directs see SEO Book’s explanation or for a more technical overview provided by Webconfs.

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Link Building, Search Engine Optimisation, Web Development