Subtitles

Text displayed on screen that represents the spoken dialogue and other relevant audio information in video content. Subtitles (called captions in North America) are essential for deaf and hard of hearing viewers but are also widely used by hearing audiences in noisy environments, for language learning, or when audio is unavailable. Closed captions can be toggled on or off by the viewer, while open captions are permanently embedded in the video. Standards like WCAG require that pre-recorded video includes synchronized captions, and that live audio content provides real-time captions. Traditional subtitle formats inherited from broadcast television impose constraints on font size and line length that limit personalisation on modern web and mobile devices.