Audio Description or Media Alternative (Prerecorded)
An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such.
In plain language
If a recorded video shows something important that isn't explained by the spoken dialogue — an action, on-screen text, a visual cue — that information needs to be narrated out loud (audio description) or described in a full text version of the video.
Why it matters
People who are blind or have low vision can hear a video but can't see what's happening on screen. If something important only happens visually and no one mentions it, that information is completely lost to them.
In practice
Fails this criterion
A video shows someone demonstrating a task silently, using only gestures and on-screen actions, with no narration explaining what they're doing and no transcript. A blind viewer has no way to know what's happening.
Meets this criterion
The same video adds narration during natural pauses in the dialogue, describing the on-screen actions. As an alternative, a full text description of everything happening in the video (like a script) is provided instead.
Exception: if the existing dialogue already explains everything shown on screen, nothing extra needs to be added.
Test it yourself
Watch the video with your eyes closed, listening only. Can you understand everything that's happening, including important visual actions and information? If something only makes sense by watching the screen, this criterion is failing.