Offer a selectable audio description track
A second audio track carrying the original soundtrack plus a narrator describing what the picture shows. G78 is that technique, and W3C counts it as sufficient for two rules with no conditions attached, one at Level A and one at Level AA. The AA one is the reason to read this page, because it means prerecorded video with a soundtrack owes audio description at the level accessibility law generally points at. The detail people get wrong is what goes on the track. It is not description by itself, it is the original audio with description added into the gaps in the dialogue. A description-only file is a different thing and players handle it differently. What gets described is actions, characters, scene changes, and any on-screen text that is not already a caption.
How we find it in an audit
First we look for the track and for the control that turns it on, since a described track nobody can select is not available. Then a reviewer listens to it end to end with the picture off, which is the only way to hear whether the description carries the visual information or narrates the obvious. Gaps in the dialogue get checked for whether they were used at all. And we confirm the described track still holds the original audio, because a track that swaps the soundtrack for narration loses the sound the video needed.
How affected users experience it
A blind viewer watching an undescribed video hears a soundtrack that assumes you can see. Silence where something happened. A presenter saying and this one is the important one, with no way to learn which one. A described track fills those gaps and changes nothing for anybody who does not select it, which makes it the least disruptive of the description routes. Everyone gets the film they expected, and one group finally gets all of it.
Passes vs. fails
Passes
An Audio description toggle switches to a track where narration reads the comparison out during the pause in the dialogue.
Fails
A product film's key moment is a silent on-screen comparison table, and the main soundtrack never mentions it.
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Video element visual content has accessible alternativeA tool finds candidates, you decide
- Video element visual content has strict accessible alternativeA tool finds candidates, you decide
Other ways to satisfy this rule
13 guides on this site are filed under 1.2.3 Audio Description or Media Alternative (Prerecorded). W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
- G8sufficientProvide a version with extended audio descriptions
- G58sufficientPut the media alternative link beside the media
- G69sufficientProvide a full transcript of the media
- G173sufficientOffer a described version of every video
- G203sufficientDescribe talking-head video with static text
- G226sufficientNarrate visual content within the soundtrack itself
This guide is our interpretation of W3C technique G78: Providing a second, user-selectable, audio track that includes audio descriptions. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.