What are Canonical Links?
A lot has been written and this is a subject that may be hard to understand for the novice so let’s break it down into some simple steps and provide a few extra resources for those who want to dig deeper.
I am going to plagiarize a bit here because, quite frankly, others have done a great job of simplifying what canonical links are. I prefer they get the credit and you get the knowledge.
What is a Canonical URL?
The best short answer I found was given by Matt Cutts: Canonicalization is the process of picking the best url when there are several choices (that is several links that take you to the same information).
Matt goes on to recommend we read more about it on Greg Grothaus Blog and we get a nice real life type example. The following links are set up perfect for the user but not so nice for SEO.
Here is a specific example:
* http://blahblahdomain.com/breadcrumbs/tents/bags/red/tent_bag.html
* http://blahblahdomain.com/breadcrumbs/bags/tents/red/tent_bag.html
* http://blahblahdomain.com/breadcrumbs/bags/tents/red/tent_bag.html?view=print
All three of the above pages are likely to have redundant information and duplicate content issues.
Canonical Link Solution:
The relatively new rel=canonical suggestion is simply to add to all 3 of these pages one single tag:
<link rel=”canonical” href=”http://blahblahdomain.com/breadcrumbs/bags/tents/red/tent_bag.html”>
You add this tag into the <head> section of the similar or identical web pages so search engines understand you have a preferred single page you want indexed in place of several that may be the same or similar in content.
This is very important for sites with a lot of varied data wherein there may be several ways to get to the exact same information at different URLs. The canonical link tag helps Google sort out the duplicate content issue and bring the preferred page to the forefront.
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