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 an HTTP Redirect on a domain name that is short, which links to the web page that has a long URL. For example, the URL <nowiki>http://en.wikipedia.org/wiki/URL_shortening</nowiki> can be shortened to <nowiki>http://wrapr.co/GvR7j</nowiki>, <nowiki>http://evg.in/az41</nowiki> or <nowiki>http://evg.in/urlwiki</nowiki>. This is especially convenient for messaging technologies such as Twitter and Identi.ca, which severely limit the number of characters that may be used in a message. Short URLs allow otherwise long web addresses to be referred to in a tweet. In November 2009, the shortened links on one URL shortening service were accessed 2.1 billion times.