Why You Should Use Canonical Tags

If you have been on the internet for more than a few months you may be aware that duplicate content is a big problem. We don’t always mean to create duplicate content, sometimes it is just a website configuration issue.

Let’s start by explaining what a canonical is. The rel=’canonical’ tag tells the search engines that the location of the page that this content is for is page XYZ. This allows you to have duplicate content pages on your site with different urls and not get hit with duplicate content issues. This does not mean that you should go and create duplicate pages on purpose.

#1) http://www.mydomain.com/handheld-widget.php

#2) http://www.mydomain.com/products/hand/handheld-widget.php

Link #1 would be our desired page to be indexed because of the shortened link string, but our store, cart, previous design, etc. allows our site to show the same item using 2 different links. We can simply tell the search engines that link #1 is the one that we prefer them to index for this content. This is done by adding the rel=’canonical’ tag in the head section of the webpage:


<title>Handheld Widget</title>

<link rel=’canonical’ href=’http://www.mydomain.com/handheld-widget.php’ />


One of the most common places that I use a canonical tag is on the home page. Many times a website will allow you to link to 1 of the 2 links below:




This situation will result in a duplicate content, but more importantly if the index.html is used, and you later change it to index.php or index.htm the links will no longer work. For this make sure you always link to the first version, and your home page has this canonical tag:

<link rel=’canonical’ href=’http://www.mydomain.com/’ />

The canonical tag can also be used in situations where 2 websites are involved. A reason for doing this would be to notify the search engines that the content is actually on another website, without redirecting the website visitor to that other website.

Additional Information:

Q: Can I use the rel=’canonical’ as a 301?

A: For the search engine’s yes, however all the link juice will not be passed to the new page like it will using a Redirect 301 will.
For an extensive look at the canonical tag see this post from February 2009 where Google Webmaster Central discussed the new canonical tag using a Swedish Fish page as their example.

Steven Ferrino
Steven Ferrino
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13th June 2011 5 Comments

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