Put a mute control before auto-playing sound
If sound starts by itself and runs past three seconds, the page owes the reader a way to stop it. G170 is that control. W3C sets four conditions on it. Near the beginning of the page, early in the tab and reading order, operable from the keyboard, and clearly labeled so a reader knows it turns off the sound that is playing. This is a sufficient technique for 1.4.2 Audio Control at Level A, one of only three W3C documents for that rule. Note where the three seconds comes from. That threshold belongs to the criterion, not to this technique, and W3C documents a separate route where the sound simply stops on its own inside three seconds. Either way, the control has to come before the noise in the reading order, because a mute button two hundred tab stops down is a button nobody reaches in time.
How we find it in an audit
Our reviewers load each page with a screen reader running and listen. Anything that starts on its own gets timed. Then we tab from the top and count how many stops it takes to reach a control that stops it. Inside a media player buried in the middle of the page is the usual answer, and that is a finding.
How affected users experience it
Automatic sound and a screen reader compete for the same channel. The speech is still playing, underneath the music, and the listener cannot turn either one down without losing both. So the first thing they have to do is find a mute button by ear, in speech they can no longer hear, which is the problem this technique exists to prevent. People with attention and cognitive disabilities lose the page for a related reason.
Passes vs. fails
Passes
The first focusable control on the page is <button id="mute">Turn off background audio</button>, and the preference holds across pages.Fails
A promo video with sound starts on page load, and the only mute control sits inside the player, two hundred tab stops into the page.
How this gets tested
The W3C publishes test rules that define what a checker looks for here.
- Audio or video element avoids automatically playing audioA tool can check this
- Audio or video element that plays automatically has a control mechanismA tool can check this
- Audio or video element that plays automatically has no audio that lasts more than 3 secondsA tool can check this
Other ways to satisfy this rule
5 guides on this site are filed under 1.4.2 Audio Control. 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.
This guide is our interpretation of W3C technique G170: Providing a control near the beginning of the web page that turns off sounds that play automatically. 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.