Twitter, Inc. was an American social media company based in San Francisco, California, which operated and was named for its flagship social media network prior to its rebrand as X. In addition to Twitter, the company previously operated the Vine short video app and Periscope livestreaming service. In April 2023, Twitter merged with X Holdings and ceased to be an independent company, becoming a part of X Corp.

X, commonly referred to by its former name Twitter, is a social media website based in the United States. With over 500 million users, it is one of the world's largest social networks and the fifth-most visited website in the world. Users can share text messages, images, and videos through posts. X also includes direct messaging, video and audio calling, bookmarks, lists and communities, and Spaces, a social audio feature. Users can vote on context added by approved users using the Community Notes feature.