What Is An Alexa Website Ranking?

Alexa Internet, Inc. is a California based subsidiary of Amazon.com, founded in 1996. Its name is an homage to the Library of Alexandria, drawing a comparison between the world’s largest repository of knowledge in ancient times and the internet today. They provide internet search engine and webcrawler services, as well as webpage archiving on behalf of the Internet Archive non-profit organization. (These archives can be accessed through the Internet Archive’s Wayback Machine digital time capsule, found at http://www.archive.org/web/web.php.)

Alexa’s ranking system tracks the popularity of internet websites planetwide. It bases its ranking schema on the level of traffic each website receives from the number of people who visit a website with the Alexa Toolbar installed. They describe it this way: The traffic rank is based on three months of aggregated historical traffic data from millions of Alexa Toolbar users 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 the geometric mean of 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).

A website’s Alexa Rank indicates how popular that site is, based on number of visitors over the last 90 days. This is a top-down ranking, with 1 indicating the most popular address, and higher numbers indicating less popular sites. For example, Ezine Articles (www.ezinearticles.com) currently has a rank of 131, meaning there are only 130 sites more popular than them. At the time of this writing, there are ~18 million sites ranked by Alexa.

It should be noted that Alexa can only collect traffic data from users who have installed the Alexa Toolbar software; since not everyone has or wants this software, it necessarily follows that Alexa cannot give a complete picture of a website’s traffic. They themselves have stated that only the top 100,000 rankings can be considered truly accurate; sites ranked above 1 million don’t receive enough Alexa-enabled traffic for their rankings to be statistically meaningful. This can be demonstrated by installing the Toolbar, visiting a site with very poor ranking (somewhere in the millions), and hitting the browser’s refresh button repeatedly – such a site’s Alexa ranking would improve dramatically within minutes, but that cannot be considered an indication of their normal traffic patterns.

Additionally, because the Toolbar collects data regarding the sites visited by users and sends this data “home” to Alexa, many vendors such as Symantec and McAfee classify the Toolbar as adware, spyware, or other potentially unwanted programs. Not everyone wants this kind of software on their computer due to privacy concerns, which limits Alexa’s audience further.

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