Search Engines Canonical Tag

On Thursday, 12th of February, Google, Yahoo and MSN officialy announced the introduction of their canonical tag which will help webmasters stop their sites falling foul of the duplicate content filter. For the less-informed amongst you, Google and other search engines cache (store in their index) different url’s related to your website. So, for example, they might see a page within a site called :

http://www.yourdomain.com/product.php?item=swedish-fish&category=gummy-candy

also accessed as
http://www.yourdomain.com/product.php?item=swedish-fish&trackingid=1234&sessionid=5678

By using the new canonical tag, you can present your preffered url like so :

<link rel=”canonical” href=”http://www.yourdomain.com/product.php?item=swedish-fish” />

The visiting bot or spider has accessed the same page via different querystring parameters (the variable and its value after the ? … item=swedish-fish) and inturn will display the example stated within the green text instead of the two examples mentioned above as the preffered url path in the search engines.

By giving the webmasters the power to choose which url they would prefer to see is a massive step in helping preffered url’s rank, ridding the search engines of duplicate content within their results (which is probably never the intention of the webmaster just the side effect of a poor performing platform, highly contributed to ecommerce sites that run querystrings in their url’s) and also harnessing link credits to a page (if their are 5 different ways to view a page there are also 5 different ways of linking to it, diluting the link strength).

The canonical tag works in the same way a 301 redirect does and should help clear the clutter for a majority of ecommerce sites out there that display querystrings in their url’s. However, be warned, that the tag is not intended to send link value from a poor performing page to a more important one, Google has already thought about that and there are checks in place if webmasters decide to manipulate the tag in this way.