Twitter is an online news and social networking service where users post and interact with messages limited to 280 characters, known as "tweets."

Registered users can post tweets, but those who are unregistered can only read them. Tweets are publicly visible by default, but senders can restrict message delivery to just their followers. Users may subscribe to other users' tweets—this is known as "following" and subscribers are known as "followers.” Follower counts provide an indicator of a Twitter account’s popularity. Individual tweets can be forwarded by other users to their own feed, a