Bitly is a URL shortening service.
URL shortening is a technique on the World Wide Web in which a uniform resource locator (URL) may be made substantially shorter in length and still direct to the required page. This is achieved by using a redirect on a domain name that is short, which links to the web page that has a long URL. For example, the URL "http://en.wikipedia.org/wiki/URL_shortening" can be shortened to "http://bitly.com/urlwiki". This is especially convenient for messaging technologies that limit the number of characters that may be used in a message, such as Twitter, and for reducing the amount of typing required if the reader is copying a URL from a print source. In November 2009, the shortened links of the URL shortening service Bitly were accessed 2.1 billion times.