Twitter is an American microblogging and social networking service on which users post and interact with messages known as "tweets". Registered users can post, like, and retweet tweets, but unregistered users can only read them. Users access Twitter through its website interface, through Short Message Service (SMS) or its mobile-device application software ("app"). Twitter, Inc. is based in San Francisco, California, and has more than 25 offices around the world. Tweets were originally restricted to 140 characters, but was doubled to 280 for non-Asian languages in November 2017.
Twitter was created in March 2006 by Jack Dorsey, Noah Glass, Biz Stone, and Evan Williams, launched in July of that year. The service rapidly gained worldwide popularity. In 2012, more than 100 million users posted 340 million tweets a day, and the service handled an average of 1.6 billion search queries per day. In 2013, it was one of the ten most-visited websites and has been described as "the SMS of the Internet". As of 2018, Twitter had more than 321 million monthly active users.