What is Alexa ?

Alexa Internet, Inc. is a California-based subsidiary company of Amazon.com that is best known for operating a website that provides information on web traffic to other websites.

Operations and history

Alexa Internet was founded in 1996 by Brewster Kahle and Bruce Gilliat in an effort to solve the internet search problem by tracking user decisions and using that data to aid future searches. From the company’s early website in 1999

Alexa Internet was created from a novel vision A vision of navigation that learns and improves over time with the collective participation of its users. We all experience the gaps in navigating and finding information on the Internet as it is used today--frustrating keyword searches that turn up hundreds or thousands of web pages and sites, very few of which are of any interest. What if we, as a community of users, could effortlessly pool our collective experience and add human intelligence to navigation? What if we could fill in those gaps? It is a radical concept and it is our goal to make it real, and we invite you to join us in this effort. What we are doing can change the way we use the Internet forever. The Alexa service is the first Internet software product that learns from people. This intelligent navigation service provides a continuous source of relevant recommendations of where to go next on the Web.

The company’s name was chosen in homage to the Library of Alexandria, drawing a parallel between the largest repository of knowledge in the ancient world to the potential for the internet if the search problem could be solved. The company offered a toolbar that gave Internet users guidance on where to go next, based on the traffic patterns of its user community.

In 1999, Alexa was acquired by Amazon.com for about $250 million in Amazon stock as the company transitioned away from its original vision of providing an intelligent search solution.

Accuracy of ranking by the Alexa Toolbar

Alexa ranks sites based on tracking information of users of its Alexa Toolbar for Internet Explorer and from integrated sidebars in Mozilla and Netscape.

On April 16, 2008 many users reported dramatic shifts in their Alexa rankings. Alexa confirmed this later in the day with an announcement that they had released the "New Alexa Ranking System" claiming that they now take into account more data sources "beyond Alexa Toolbar users".

“The traffic rank is based on three months of aggregated historical traffic data from millions of Alexa Toolbar users and data obtained from other, diverse traffic data sources, and is a combined measure of page views and users (reach). As a first step, Alexa computes the reach and number of page views for all sites on the Web on a daily basis. The main Alexa traffic rank is based on a value derived from these two quantities averaged over time (so that the rank of a site reflects both the number of users who visit that site as well as the number of pages on the site viewed by those users). The three-month change is determined by comparing the site’s current rank with its rank from three months ago. For example, on July 1, the three-month change would show the difference between the rank based on traffic during the first quarter of the year and the rank based on traffic during the second quarter.”