WCAG 2.2 success criterion 1.2.4, Captions (Live), is a Level AA requirement: live audio in synchronised media is captioned.
Read the criterion in the W3C Recommendation, WCAG 2.2 (opens in a new tab).
How BearScan checks it
Live audio in synchronised media is captioned
Checked automatically: loads the page in a browser. Severity: high. A live stream without captions excludes deaf and hard-of-hearing viewers from the event entirely, and there is no recording to fall back on.
An approximation: A stream is live when a page fetches an HLS playlist with no end marker or a DASH manifest of type dynamic, or embeds a frame at the address of a live player (YouTube live, Twitch, Vimeo events). The manifest is read for a captions or subtitles track; a stream that lists none fails. The media itself is never played, so how accurate live captions are is not judged, an embedded player's captions cannot be read from its address (reported for review), and a stream that starts only when a visitor clicks play, or on a schedule, is not seen. A page with no live stream is not applicable.
How to fix it. Caption every live stream in real time, using a human captioner (CART) or a live-captioning service whose accuracy has been checked, and make the captions available in the player.
All WCAG 2.2 criteria · Next: 1.2.5 Audio Description (Prerecorded)
Questions
Is WCAG 1.2.4 required by the ADA?
The ADA doesn't name a technical standard for businesses, but the Justice Department's 2022 guidance points businesses to WCAG, and its 2024 rule for state and local governments adopted WCAG 2.1 Level AA, which includes 1.2.4.
Can an automated tool check WCAG 1.2.4?
Mostly. BearScan checks it automatically (loads the page in a browser). A clean result still isn't proof every page passes, only the pages scanned.
How do I fix a WCAG 1.2.4 failure?
Caption every live stream in real time, using a human captioner (CART) or a live-captioning service whose accuracy has been checked, and make the captions available in the player.