Twitter is an online news and social networking service where users post and interact with messages, called "tweets." These messages were originally restricted to 140 characters, but on November 7, 2017, the limit was doubled to 280 characters for all languages except Japanese, Korean and Chinese. Registered users can post tweets, but those who are unregistered can only read them. Users access Twitter through its website interface, Short Message Service (SMS) or mobile device application software ("app"). Twitter, Inc. is based in San Francisco, California, United States, and has more than 25 offices around the world.