Nielsen is described as 'Whether you're eyeing markets in the next town or across continents, we understand the importance of knowing what consumers watch and buy. That's our passion and the very heart of our business' and is an app in the Web Browsers category. There are more than 10 alternatives to Nielsen for a variety of platforms, including Online / Web-based, iPhone, Linux, iPad and Mac. The best alternative is Alexa. It's not free, so if you're looking for a free alternative, you could try Site Rank Data or Quantcast. Other great apps like Nielsen are Website Informer (Free), ComScore Media Metrix (Free), SEO camel (Free) and Ego (Paid).