Alexa is an Internet service that measures how many Internet users visit a website. At Alexa.com, people can enter a website address and Alexa will show them how well-visited the website is. It can also tell them how its popularity has changed over time. Alexa have 6 million unique visits monthly.
Alexa was created in 1996 by American businessman Brewster Kahle and Bruce Gilliat. In 1999, Alexa was bought by Amazon.com for about US$250 million in Amazon stock. Alexa provides free api that is used by services and toolbars all around the world to easily display Alexa Rating.