SEO – Avoiding Duplicates with Canonical URL Tags

You may have seen my article about the Ultimate Noindex Nofollow tool for WordPress, but avoiding duplicate content can help the search engine ranking of any web site, including static sites.

Recently, Yahoo!, Live, and Google all agreed to support Canonical URL Tags. You put a line of code into the head section of your document like the one below:

<link rel="canonical" href="" />

This tells the search engines that this page URL should be regarded as a copy of and that any link or content metrics should be applied to that URL.

When your site contains multiple URLs to the same content (for example blogs and ecommerce platforms can contain links to the same articles or products via the home page, category pages, search results, etc. each creating its own path to the same article or product), your search ranking suffers. The search engines don’t know which ones to index or rank, and your metrics get spread out over all the streams instead of always pointing to the ultimate URL of the individual piece of content.

Examples of links that might point to the same content are:


This happens because this article currently appears on both my home page as well as the page for the category that the post is assigned to, but the “real” URL to this post that I actually want Google to index is (currently):

(yeah, I know I haven’t dressed up my permalinks yet – one thing at a time)

Makes sense?

This article copyright © John Nasta 2009 – All Rights Reserved
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