While video subtitles are intended for viewers who can’t understand the language being spoken, captions are intended for viewers who can’t hear the audio. Captions (which can refer to closed captions or open captions) include the dialogue as well as any other relevant audio. They are used to aid the hard-of-hearing by communicating all audio sounds including sound effects, speaker IDs, and other non-speech elements. For most video content, captions are required under United States law. Users can often change the visual display of captions, and their placement on the screen can move to prevent any obstruction of the visual images being presented.