Alexa Internet

Alexa Internet is a California-based subsidiary company of Amazon.com, that is best known for operating a website (www.alexa.com) that provides information on the web traffic to other websites. Its premises are in Building 37 of the Presidio of San Francisco.

Founded in 1996 by Brewster Kahle and Bruce Gilliat and backed by Jacqui Safra's Etoile Investments as a commercial offshoot of the Internet Archive, Alexa Internet created related links derived from user behavior (a form of collaborative filtering) for users of the Internet Explorer and Netscape Navigator web browsers. Engineers at Alexa created the Internet Archive's Wayback Machine. Alexa also supplies the Internet Archive with web crawls. It should be noted that Alexa's official toolbar only works with a Windows/Internet Explorer 5.0+ though there is a plugin for Mozilla Firefox called [http://www.quirk.biz/searchstatus/ search status that accesses both Google and Alexa feeds.

In 1999, Alexa was acquired by Amazon.com for about $250 million in Amazon stock.

Alexa collects information on Web usage through the Windows-only / Internet Explorer-only application, the Alexa Toolbar. This allows them to provide statistics on web site traffic, as well as related link information. The Alexa Toolbar has a bad reputation with anti-spyware programs, as it collects information on search habits.

The "site info" link on the Alexa site lists related links for websites and also records how much web traffic they receive. Alexa began a partnership with Google in spring 2002, and with the Open Directory Project in January 2003. Windows Live Search replaced Google as a provider of search results in May 2006. Today, Alexa is primarily a Windows Live Search-based search engine, an Open Directory-based web directory, and a supplier of site information.

Alexa also provides "site info" for the A9.com search engine and for Alexadex.com.

In December 2005, Alexa opened its extensive search index and web-crawling facilities to third party programs through a comprehensive set of web services and APIs. These could be used for instance to construct vertical search engines that could run on Alexa's own servers or elsewhere.

Alexa rank information

Alexa ranks sites based on visits from users of the Alexa Toolbar which is only available for Internet Explorer and must be manually installed. There is some controversy over how representative Alexa's user base is of typical internet behavior. If Alexa's user base were a fair statistical sample of the internet user population (e.g. a random sample of sufficient size), Alexa's ranking would be quite accurate (see Sampling). In reality, the sample is not random and has many sources of bias. Alexa itself notes several (here and here)

Sites that are featured on alexa.com are overrepresented.
Users running Firefox, Opera or other browsers are not represented.
Users running browsers on mobile phones are not represented.
Users running Apple or Linux machines are not represented.
Unknown bias with respect to operating systems.
Visits to secure pages (https:) are not taken into account.
Users who do not install toolbars are not represented.

As a result of these biases, sites with a large share of visitors who use non-IE browsers or are running on Linux or Mac OS X will appear quite low in Alexa rankings. Sites serving pages over secure connection or having large share of users concerned about privacy will also rank low.

In addition, the sample used for estimation is small comparatively to the population of all web users. Sites with low traffic can be completely missed in this small sample. Another concern connected here is that Alexa ratings are easily manipulated. Webmasters can significantly improve the Alexa ranking of less popular sites by making them the default page and by having Alexa toolbar installed. (ref)

Alexa provides an important, useful, and, for most websites, also independent source of information about website traffic. It reports some share of the traffic created by Alexa toolbar users. We can infer that the total traffic of the website is no less than what Alexa reports (but may be much more, since Alexa fails to account a large number of visitors). Unfortunately, Alexa's rankings are often misinterpreted as an exact or approximate measure of popularity of web sites.

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Alexa rank information

See also

External links