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Created in 2006 by developer Jack Dorsey as a tool to keep in touch with friends, Twitter is a web-based social networking service that allows users to send and read short messages (called tweets).[1]

"Twitter is a social media platform with more than 300 million active users worldwide, including some 70 million in the United States."[2]


Also considered a microblogging site, Twitter users send tweets of up to 280 characters.[3].These tweets are displayed on an author's Twitter home page and on the pages of people subscribed to his or her RSS feed.

Twitter enables individual users to post thoughts on any number of topics or activities. While Twitter use varies, it has been used by individuals and organizations to state opinions, promote events, and announce the release of products and services.

Because of the 140 (now 280) character limit on tweets, Twitter messages are necessarily short. The brevity of the messages highlights the ease with which tweets can be quickly sent from mobile devices to followers around the world. The rapid transmission of information allows individuals and groups to communicate instantly without limitation of physical distance.

Senders can restrict delivery to those in their circle of friends or, by default, allow open access. Users can send and receive tweets via the Twitter website, Short Message Service (SMS) or external applications. While the service itself costs nothing to use, accessing it through SMS may incur phone service provider fees.

Twitter allows individual users to "follow" other Twitter subscribers and read their tweets from the Twitter homepage. Individuals may choose to follow another Twitter account if they are interested in the information provided, are friends with the Twitter account holder, or if they are a "fan" of an activity or place. Following another user’s Twitter account allows for almost instant access to his or her tweets. This can be useful if a follower is looking for a featured item or to better understand the activities of the person or group he or she is following. Individuals who "follow" an individual Twitter user can have instant access to tweets through devices such as a Blackberry, iPhone, Android, or other similar mobile, internet-ready devices.

How it works[]

Tweets may include photographs, videos, and links, and are posted to a webpage on Twitter that is attached to the user's account. An individual "tweet" comprises the tweeted content (i.e., the message, including any embedded photograph, video, or link), the user's account name (with a link to the user's Twitter webpage), the user's profile picture, the date and time the tweet was generated, and the number of times the tweet has been replied to, retweeted by, or liked by other users.

The Twitter webpage that displays the collection of a user's tweets is known as the user's "timeline." When a user generates a tweet, the timeline updates immediately to include that tweet, and anyone who can view a user's Twitter webpage can see the user's timeline.

A user's Twitter webpage may also include a short biographical description; a profile picture, such as a headshot; a "header" image, which appears as a banner at the top of the webpage; the user's location; a button labeled "Message," which allows two users to correspond privately; and a small sample of photographs and videos posted to the user's timeline, which link to a full gallery. By default, Twitter webpages and their associated timelines are visible to everyone with internet access, including those who are not Twitter users. However, although non-users can view users' Twitter webpages (if the accounts are public), they cannot interact with users on the Twitter platform.

A defining feature of Twitter is a user's ability to repost or respond to others' messages, and to interact with other Twitter users in relation to those messages. Beyond posting tweets, Twitter users can engage with one another in a variety of ways. First, they can "retweet" — i.e., repost — the tweets of other users, either by posting them directly to their own followers or by "quoting" them in their own tweets. When a user retweets a tweet, it appears on the user's timeline in the same form as it did on the original user's timeline, but with a notation indicating that the post was retweeted. Second, a Twitter user can also reply to other users' tweets. Like any other tweet, a reply can be up to 280 characters in length and can include photographs, videos, and links. This reply may be viewed in two places: when a user sends a reply, the reply appears on the user's timeline under a tab labeled "Tweets & replies." However, the reply may also be accessed from the feed of the user sending the tweet being replied to: by clicking on the tweet that prompted the reply, the reply will appear below the original tweet, along with other users' replies to the same tweet.

Third, a Twitter user can also "favorite" or "like" another user's tweet by clicking on the heart icon that appears under the tweet. By "liking" a tweet, a user may mean to convey approval or to acknowledge having seen the tweet. Fourth, a Twitter user can also "mention" another user by including the other user's Twitter handle in a tweet. A Twitter user mentioned by another user will receive a "notification" that he or she has been mentioned in another user's tweet. Finally, Twitter users can subscribe to other users' messages by "following" those users' accounts. Users generally can see all tweets posted or retweeted by accounts they have followed. Tweets, retweets, replies, likes, and mentions are controlled by the user who generates them. No other Twitter user can alter the content of any retweet or reply, either before or after it is posted. Twitter users cannot prescreen tweets, replies, likes, or mentions that reference their tweets or accounts.

Because a retweet or a reply to a tweet is itself a tweet, each retweet and reply, recursively, may be retweeted, replied to, or liked. A Twitter user can also reply to other replies. A user whose tweet generates replies will see the replies below his or her original tweet, with any replies-to-replies nested below the replies to which they respond. The collection of replies and replies-to-replies is sometimes referred to as a "comment thread." Twitter is called a "social" media platform in large part because of comment threads, which reflect multiple overlapping "conversations" among and across groups of users.

In addition to these means of interaction, Twitter offers two means of limiting interaction with other users: blocking and muting. First, a user who wants to prevent another user from interacting with her account on the Twitter platform can do so by "blocking" that user. (Twitter provides users with the capability to block other users, but it is the users themselves who decide whether to make use of this capability.) When a user is signed in to a Twitter


  1. Twitter, "Where did Twitter Come From?," About Twitter (full-text). For more information about social networking see danah m. boyd and Nicole B. Ellison, "Social Networking Sites: Definition, History, and Scholarship," 13 J. of Computer-Mediated Comm. 210-30 (Oct. 2007); and Lee Humphreys, "Mobile Social Networks and Social Practice: A Case Study of Dodgeball," 13 J. of Computer-Mediated Comm. 341-60 (Oct. 2007).
  2. Knight First Amendment Institute at Columbia University v. Trump, 2018 WL 2327290, at *1 (S.D.N.Y. 2018).
  3. Originally, users were limited to 140 characters per tweet. The limit has since been increased to 280 characters. See Aliza Rosen, Tweeting Made Easier, Twitter (Nov. 7, 2017) (full-text)


  • How it works section: Knight First Amendment Institute at Columbia University v. Trump, 2018 WL 2327290, at *2–*3 (S.D.N.Y. 2018) (based on the parties' stipulated facts; quote marks and citations omitted).