Add audio description tracks to video
A track element with kind=descriptions carries timed text describing what happens on screen, the actions and scene changes and on-screen words the soundtrack leaves out. W3C lists H96 as advisory for every criterion it touches, which means it satisfies none of them on its own. There is a plain reason for that. When the working group last reviewed the technique, in September 2023, no browser had native support for speaking these tracks, and the working route is a JavaScript polyfill. The format also has a hard limit built into it. A description has to fit the gap in the audio, and where there is not enough time the speech gets cut off. That is why extended audio description, where the video pauses until the description finishes, exists as a separate idea. So most teams meet the rule with a described audio mix or a separate described version, and keep the descriptions track as the standards-based way to carry the same content.
How we find it in an audit
A tool can tell you whether a descriptions track exists. It cannot tell you whether the video needed one, so we watch each video with the screen off and write down every plot-relevant thing the soundtrack skipped. Then we put that list next to whatever the description track or the described version actually covers.
How affected users experience it
A blind viewer gets the soundtrack and nothing else. In a screencast where the presenter says just click this and it works, the described version is the thing that says what this was. Without it the tutorial teaches nothing, and the silence where the description should have been is exactly the part of the video that was carrying the instruction.
Passes vs. fails
Passes
<track kind="descriptions" src="demo.desc.vtt" srclang="en" label="English descriptions">
<!-- or rewrite the narration to say "select Export, the third item in the File menu" -->Fails
A tutorial video whose narration says now select the highlighted option and never names the option.
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Audio element content has text alternativeA tool finds candidates, you decide
- Video element visual-only content has accessible alternativeA tool finds candidates, you decide
- 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
The other techniques filed under this rule
6 guides on this site are filed under 1.2.1 Audio-only and Video-only (Prerecorded). W3C lists this one as advisory for that rule rather than sufficient, which means it helps real readers without being accepted as evidence you conformed.
This guide is our interpretation of W3C technique H96: Using the track element to provide 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.