Alexa Internet Inc. is a service for tracking the usage and views of websites on the internet.
Alexa tracks the browsing behavior of users who installed the Alexa toolbars to generate site ranks and statistics. Because there is little to no information about who uses the toolbar, Alexa rankings should not be considered to be completely accurate or representative. However, it is often used to compare traffic and usage of websites because sites usually don't post much reliable information in public.
Alexa is owned by Amazon.com, a major CIA contractor.