Twitter is a social network and microblogging platform.
The service is built on 140-character messages called tweets, which live on the web and can be read by anyone, although some users opt to make their accounts private. Twitter also allows users to “follow,” or subscribe to, other users’ tweets and — through replies to and retweets of other users — interact with one another. The service is used for everything from casual social interaction to the reporting of breaking news.
Twitter was founded in 2006 by Jack Dorsey as a side project of the podcasting company Odeo. The project first garnered widespread attention at the 2007 South by Southwest Festival in Austin, Texas.
Twitter was estimated in September 2013 to have more than a billion registered users, who generate some 1 billion tweets per week. The service has seen exponential growth since mid-2008, though many of its users are inactive — just 271 million of its more than 1 billion users were active as of 2014.
Twitter provides an open API, which has allowed developers to create more than 100,000 applications as of April 2010 and 750,000 as of March 2011, and also contains tweets’ increasingly valuable metadata. Many of its most widely used features, such as @replies and hashtags, were created by users in a process of end-user innovation. Twitter’s relationship with third-party developers began to chill, however, in March 2011, after the company suggested that developers stop creating “apps that mimic or reproduce the mainstream Twitter consumer client experience.” It reinforced that warning in a June 2012 post and continued to alienate many developers with another tightening of its rules in August 2012.