Duplicate content (or duplication of content) is a recurring subject in natural referencing, since the end of 2006 Google regularly communicates on it in order to limit the effects of it. The engine does not just communicate, it also regularly offers tools so that webmasters can control the URLs of their sites in order to avoid duplication of content …
Tools to fight against duplication of content…
Advice on redirection 301, possibility via Google webmaster tools to select your preferred domain, rel canonical attribute… There is already enough to do in the fight against duplicate content.
But Google does not want to stop there: today, it announces a new service: “parameter handling” this tool is particularly useful for sites with many parameters in their URLs such as e-commerce sites for example, it will allow you to tell Google which parameters are important and which can be ignored.
Example : an e-commerce site can display the same page under 2 URLs with different parameters depending on how the user navigates on the site:
In these URLs, we see several parameters: item, category, trackingid, sessionid. Via the tool we will be able to indicate which parameter is not important and can be ignored. After that, the crawl of your site can be done more adequately.
One more tool for SEO 🙂
Source: Webmaster central blog