In SEO, the term canonicalization refers to the process wherein URLs are standardized. What this simply means is that it is how you establish, or tell search engines, which URL you want them to display in search results as containing a certain document.
Canonicalization can be a big problem in SEO as search engines see different URL versions of the same page (i.e. http://www.phoenixrealm.com/ and http://phoenixrealm.com/) can lead to the following issues:
- having the URL versions flagged for containing duplicate content;
- having a non-preferred URL rank higher than the URL you prefer your users to land on; and
- splitting the link juice between the URLs.
To fix this issue, what you need to do is just let the search engines know that these URLs really just have one content and that there is one URL which you prefer them to show in their SERPs. To do this all you need to do is use the canonical tag.
The canonical tag is recognized by all the major search engines and is very easy to use. You just need to add the rel=”canonical” attribute as a link element to all the head pages of the non-preferred URLs. For the example above, if the preferred URL is the first one, then add
<link rel=”canonical” href=”http://www.phoenixrealm.com/“>
to the head section of the second URL so that the search engines will route all the link juice to the first URL and also only show that in their result pages.