Perceivable · 1.2 Time-based Media
Prerecorded video with sound must have either audio description of important visual information or a full text alternative describing both what is seen and what is heard. Media that is a clearly labeled alternative for text is exempt.
Live demo
The same task, done two ways: switch between the version that passes and the one that fails, or put them side by side. Everything in the box is live, so try it with a keyboard, a pointer or a screen reader.
Press play and close your eyes. In Passes a second voice says what is on screen; in Fails you hear "turn this" but never learn what it is.
A short help video from your energy supplier.
A short help video from your energy supplier.
The tools follow the version you last used.
What happened
Why it passes
In the pauses, a voice describes the dial, the blue tap, the flame button and the helpline number. A blind viewer can follow every step.
Why it fails
Marco says "this dial" and "this button". Without description, a blind viewer never learns which tap to turn or which number to call.
Examples
Four examples, each one running: the usual ways this criterion fails, and code that passes. Listen to them, measure them, or copy the code.
Fails
Live preview
<video controls src="/help/boiler-reset.mp4"></video><details> <summary>Transcript</summary> <p>Marco: Check this dial. If the needle is in the red, turn this until it clicks.</p> <p>Marco: Then hold this button for five seconds.</p></details>The transcript repeats only the speech. "This dial" and "this button" mean nothing to someone who cannot see the video.
Passes
Live preview
<video controls src="/help/boiler-reset.mp4"></video><details> <summary>Text version, with descriptions</summary> <p>[Marco points to the round pressure dial on the front of the boiler.]</p> <p>Marco: Check this dial. If the needle is in the red, turn this until it clicks.</p> <p>[He turns the blue tap under the boiler. The needle rises out of the red.]</p> <p>Marco: Then hold this button for five seconds.</p> <p>[He holds the button marked with a flame. A green tick appears.]</p></details>Descriptions of the actions sit between the lines of speech, so a blind or deafblind reader learns which dial, tap and button to use.
Fails
Live preview
<video controls src="/help/boiler-reset.mp4"> <track kind="captions" src="/help/boiler-reset.en.vtt" srclang="en" label="English"></video>Captions help deaf viewers, but the tap, the button and the helpline number are only shown. Blind viewers get no description and no text version.
Passes
Live preview
<video controls src="/help/boiler-reset.mp4"> <track kind="captions" src="/help/boiler-reset.en.vtt" srclang="en" label="English"></video><p><a href="/help/boiler-reset-described/">Watch with audio description</a></p>The described version adds narration of each action in the pauses. The link sits right under the player, so it is easy to find.
Why it matters
People who are blind or have low vision learn about actions, on-screen text and scene changes they cannot see, and a text alternative also serves deafblind people using braille.
W3C: Understanding 1.2.3Level A
Level A is the minimum: failing it can shut some people out completely.
Where it is required
Required where the law names WCAG 2.0 or later at this level: the United States, Canada, the European Union, the United Kingdom, France, Germany, Italy, Spain, the Netherlands, Ireland, Switzerland, India, Japan, Australia, New Zealand and Israel.
How to test
A few concrete steps. Automated tools find some failures; most need a person.
Common failures