A reaction video, or a react video,[1] is a video in which one or more persons react to something. Videos showing the emotional reactions, criticism or commentary of people viewing movies, television series episodes, film trailers, music videos, news, or other media are numerous and popular on online video hosting services such as YouTube and live-streaming services such as Twitch. The depicted persons may not even be aware that they are being recorded. In many cases, the video to which people are reacting is shown within the reaction video, letting viewers see what is being reacted to.
The question of if, and when, reaction videos constitute a fair use of intellectual property, rather than an appropriation of the reacted-to content, and a copyright infringement, has generated controversy and is a subject of discussion and debate.