Alexa Internet

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Alexa Internet is a California-based subsidiary company of, that is best known for operating a website ( that provides information on the web traffic to other websites. Alexa collects information from users who have installed an Alexa Toolbar, allowing them to provide statistics on web site traffic, as well as lists of related links.


[edit] Operations and history

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.

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

The company's premises are in Building 37 of the Presidio of San Francisco.

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. In September 2006 they began using their own Search Platform to serve results. Today, Alexa is primarily a search engine, an Open Directory-based web directory, and a supplier of site information.

Alexa also provides "site info" for the search engine.

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.

[edit] Alexa rank information and the Alexa Toolbar

Alexa ranks sites based on visits from users of its Alexa Toolbar which is only available in English, for Internet Explorer and must be manually installed. A third-party extension for Mozilla Firefox called SearchStatus was made available in May 2006; it allows users of this browser to view Google and Alexa rankings of a visited site and thereby also affect Alexa rankings.

Alexa Toolbar is considered spyware by many because it often 'piggybacks' on other software. This means that, when a user installs unrelated software, Alexa Toolbar may also be installed, sometimes without the user's knowledge. Many people object to this surreptitious installation method.

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 statistical bias. Alexa itself notes several examples (here and here):

Bias towards English-speaking users   Alexa's toolbar is available only in English, users speaking other languages are not represented.
Preferential bias towards Alexa-listed sites   Sites that are featured on Alexa are overrepresented.
Omission of some browsers   Users running any browser except Internet Explorer (and unofficially Mozilla Firefox) are not represented.
Omission of sites and visits using secure https, RSS or other non-HTML feeds   Visits to secure pages and RSS feeds are not taken into account. Some sites serve a high proportion of these pages. RSS services and users are also under-represented from sites that serve both html and RSS because RSS feed-reading and aggregation software can't use the Alexa toolbar and so are not counted.
Omission of non-toolbar users   Users who do not install toolbars are not represented. Notably, this includes most corporate and work users, and most users of public computers such as those at libraries.
Omission of users with spyware/adware blockers   Users running spyware and adware prevention or removal programs that report Alexa as spyware are under-represented or ignored.
Bias towards pre-installed default homepages   Many users never bother to change the default homepage their browser comes pre-installed with, even though they rarely if ever intentionally visit that site. However Alexa will still count a visit to that site every time those users start up their browsers. This contributes to the high Alexa ranking of, the default homepage on many Windows installations.
Bias towards inexperienced internet users   Novice users fall disproportionately into a number of the above categories. They are more likely to use browser toolbars and, by default, Internet Explorer, and less likely to change their default homepages, install spyware blockers, and utilize RSS feeds.

As a result of these biases, sites with a large share of visitors who use alternative browsers or operating systems will appear disproportionately low in Alexa rankings. Sites serving pages over secure connection or having large share of users concerned about privacy will also rank lower.

Another concern connected here is that Alexa ratings are easily manipulated. Some webmasters claim that they can significantly improve the Alexa ranking of less popular sites by making them the default page, by exchanging web traffic with other webmasters, and by requiring their users to install the Alexa toolbar[1]; however, such claims are often anecdotal and are offered without statistics or other evidence. To the contrary, traffic patterns seen on Alexa often strongly correlate with other sources of data.

Several file upload services have top Alexa rankings because they required their non-US and non-European visitors to install the Alexa toolbar in order to use the site's services.

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. Unfortunately, Alexa's rankings are often misinterpreted as an exact or approximate measure of popularity of web sites.

[edit] See also

[edit] External links

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Alexa Internet

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