• Success Criterion 1.2.1
  • Conformance level A

Video’s Narrated Audio Track Skips Key Visual Details

1.2.1 — Audio-only and Video-only (Prerecorded)

Scenario

Setting

A community forum's discussion thread

What’s wrong

Video-only media whose audio-track alternative doesn't describe all important visual information.

Example 

<video src="/forum/derailleur-fix.mp4" controls></video>
<!-- Narration: "Loosen this screw, then adjust here until it clicks."
     On-screen arrows and a torque number are never named aloud. -->

Why it matters

A blind hobbyist following the audio alone hears "loosen this screw" with no indication of which screw or how many turns, since the on-screen arrow and number are never spoken.

How to test

Read the audio-track alternative for a video against the video itself: check it also states what's shown on screen, not just what's said.

How to fix

When a video's soundtrack is meant to stand in for the visuals, it has to name every part and value the video points to, not just "this" and "here."

<video src="/forum/derailleur-fix.mp4" controls></video>
<!-- Narration: "Loosen the barrel adjuster, the small knurled screw
     near the cable, one full turn counterclockwise until it clicks." -->

Outcome

A blind hobbyist follows the narration alone and adjusts the correct part by the right amount.

Who is affected

Blind users relying solely on the audio track miss the specific part names and numeric values that only appear as on-screen graphics.

Learn more

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