Time-Based Media
Learn about required alternatives and accessibility features for video and audio content.
WCAG has several guidelines related to time-based media, which typically has a video and/or audio component.
In general, these guidelines are about providing ways to consume information that are not dependent on a specific sense. For example, audio content requires the sense of hearing. WCAG compliance requires having versions of equivalent content that don’t rely on hearing, such as adding closed captions to videos or providing transcripts of audio-only files.
Three of the most important accessibility components for time-based media are captions, transcripts and audio descriptions.
Captions
For all video files, there must be synchronized and accurate closed captions.
Captions display spoken dialogue or narration, including speaker identification, as well as sound effects and music description. Captions are synchronized with the video and are displayed on top of it.
Closed captions are different from subtitles because they include sounds that are important to understanding a scene in addition to dialogue.
Learn more about 1.2.2 Captions – Prerecorded (Level A)
Learn more about 1.2.4 Captions – Live (Level A)
Transcripts
A transcript is the textual version of the multimedia audio content. It may contain additional descriptions, explanations or comments, such as auditory action and background noise in addition to dialogue. A transcript is usually a text document without any time information, but may also be included on a webpage.
Transcripts can provide textual alternatives for audio-only content (such as podcasts) or videos that contain audio tracks.
Learn more about 1.1.1 Non-text Content (Level A)
Audio Descriptions
Audio descriptions are commentary and narration that guide the listener through a video or presentation. They should use concise, objective descriptions of scenes, settings, costumes, body language and more. Audio descriptions are intended for users with visual disabilities, providing additional information about what is visible on the screen — such as actions, scene changes, facial expressions and on-screen text.
Descriptive audio tracks can be added to videos that don’t have default audio and to videos that have a default audio track.
Learn more about 1.2.3 Audio Description or Media Alternative – Prerecorded (Level A)
Learn more about 1.2.5 Audio Description – Prerecorded (Level A)
Additional Resources
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