Quantcast is a team of web analytics experts building powerful statistical technology to understand internet audiences. Quantcast helps web publishers of all sizes understand the composition of their audiences and attract higher advertising rates, and helps advertisers and agencies find elusive online audiences wherever they might be. This web site allows anyone to view audience reports on hundreds of thousands of websites.
Think of Quantcast for ratings, as Alexa is for websites. Altough their estimates are not bulletproof or 100% accurate, you can discover and approximate pretty useful information.
How does Quantcastâ€™s ratings system work?
Quantcastâ€™s audience ratings are based on the analysis of massive amounts of internet usage data. How massive? Billions of web site visits every month. By analyzing this data we are able to interpret patterns of internet usage and provide the reports that you see here.
Find out more about their estimates or how can you correct errors in your website’s report.
Here are some examples of their reports: Digg.com, Seomoz, Reddit, New York Times, Alexa.com or SearchEngineWatch.com.