Google, Yahoo and Microsoft have just announced a new tag, which we can use to tell the search engines which URL it should have for the current page. They want to clean up duplicate urls on sites. The syntax is pretty simple:

An ugly url such as http://www.example.com/page.html?sid=asdf314159265 can specify in the HEAD part of the document the following:

<link rel="canonical" href="http://example.com/page.html"/>

That tells search engines that the preferred location of this url (the “canonical” location, in search engine speak) is http://example.com/page.html instead of http://www.example.com/page.html?sid=asdf314159265 .

Check out this video by Matt Cutts of Google who explains the new element in-depth:

There are already some plugin for WP Canonical links, or e-commerce Magento plugin canonical URL’s extension, and Drupal CMS.

I would love to hear what you think about the canonical links.