Search engines to honor new “canonical” URLs to reduce content duplication
This is hot off the presses, folks.
Google, Yahoo, and Microsoft announced today that their search engines will honor a new value for the rel attribute of link elements commonly found in the head element of a web page. This new specification aims to reduce content duplication via redundant URLs.
For instance, WordPress posts can be accessed always through the URL example.com/index.php?p=3 and often through a URL such as example.com/2009/02/12/search-engines-to-honor-canonical-urls or the like. Search engines see these separate URLs and usually think that they are duplicate content at different URLs, thus reducing the site’s ranking because of the duplicate content.
The new functionality acts not unlike a soft 301 redirect.
Check out the very informational post at Search Engine Land on the new canonical URLs. A big thanks to @badmacktuck for bringing it to my attention!
Joost de Valk wrote a WordPress plugin called wp-canonical which adds such a link element to any WordPress blog. I’m using it now. He’s also written a Drupal plugin and an informative blog about about canonical URLs, too. That was quick!
badmacktuck:
Thanks for the shout-out! This is potentially a game changer for a lot of people.
One thing they stressed over and over again in the session, is that you need to be very cautious when using this feature.
12 February 2009, 6:25 pmColin Dean:
Yes, indeed. The power to have multiple ways to access content but have search engines always give folks a certain URL when coming from a search engine is quite useful. I wonder how long it will be until someone comes up with a neat technique which takes advantage of canonical URLs in order to raise their ranking even higher.
12 February 2009, 6:33 pm