Alexa’s traffic rankings are based on the anonymous usage patterns of one of the largest and most global samples of internet users available in the world. This web service enables developers to add high-quality web traffic intelligence directly into their web sites and applications. This data can be used internally to make business decisions such as where to most effectively advertise, or externally, when prioritizing aggregated information on a web site. Whether seeking the top 100,000 web sites in the world, or the top 1,000 in the U.S., the Alexa Top Sites web service allows developers to programmatically receive rankings for web sites in over 70 countries.

A site’s ranking is based on a combined measure of reach and page views computed over a trailing 3 month period. Reach is determined by the number of unique Alexa users who visit a site on a given day. Page views are the total number of Alexa user page requests for a site. However, multiple requests for the same page (URL) on the same day by the same user are counted as a single page view. The site with the highest combination of users and page views is ranked #1.