WCAG 1.2.4 Captions (Live)

What it asks

This is the live counterpart of 1.2.2 Captions (Prerecorded). It covers synchronised media that is happening in real time: webinars, live streamed events, live lectures, product launches and streamed town halls. The captions have to be provided while the event is live, not added to the recording afterwards.

Live captions are usually produced by a trained captioner working from the audio, or by automatic speech recognition, often with a person correcting it. The criterion does not say which. It says the captions must be there. Quality still matters, and automatic captions on a live event with specialist vocabulary and several speakers can be hard to follow.

The rule covers live video with sound. Live audio-only content, such as a radio stream, is not covered by this criterion; it is a Level AAA matter under 1.2.9. A video stream with no sound is also outside it.

For most websites this criterion is Not Applicable, because they broadcast nothing live. For a product that hosts live events, it is usually answered by the platform the events run on, which is why conformance reports often rest on the vendor’s own statement here.

Its official name is success criterion 1.2.4 Captions (Live), at Level AA. It was added in WCAG 2.2, under guideline 1.2 Time-based Media and the principle Perceivable. The W3C’s normative text says, in part:

“Captions are provided for all live audio content in synchronized media.”

From WCAG 2.2, W3C. Full explanation: Understanding 1.2.4 Captions (Live).

Who it helps

Deaf and hard of hearing people, who otherwise cannot take part in a live event at all. A recording with captions published a week later is not the same as being there, asking questions and hearing the answers.

It also helps people in noisy or quiet places, and anyone for whom the speaker’s accent or the connection makes the audio hard to make out.

What passes and what fails

These pass

• A webinar platform with a live captioner, and the captions shown in the player as the speaker talks.
• A live stream on a video service with its live captions turned on by the host.
• An online conference with live captions on every session by default, not on request.
• A company that broadcasts nothing live. The criterion does not apply.

These fail

• A webinar platform that captions the recording afterwards but shows nothing live.
• Live captions offered only when an attendee asks in advance, so a person joining on the day has none.
• A live product launch streamed to a page with a player that has no captions control.
• A live event on a service that supports captions, where the host never switched them on.

How to test it by hand

1. List every place the product broadcasts live video with sound: webinars, streams, events and live classes.
2. For each, join a live session, or ask the people who run them, and check whether captions appear in real time.
3. Check whether captions are on by default or have to be requested, and how far in advance.
4. If captions are automatic, watch a session and note whether they keep up and whether names and terms come through.
5. If the product broadcasts nothing live, record that as the reason the criterion does not apply.

What automated testing can decide

What a machine can decide

Automated testing can notice that a page carries a live stream: a live player embed, a live-flagged media element or a known streaming service. That tells an auditor the criterion applies. Where no page carries anything live, having looked is the evidence for a Not Applicable result.

What it cannot

Whether captions appear during a live event is not on the page before the event, and often not on it during. It depends on how the host has set up the platform and who is captioning on the day. No test of a page can see any of that. This criterion is answered by watching a live session, or by the organisation stating how its live events are captioned.

How Dreven handles it

Dreven looks for live media on your pages. Where there is none, the report says the criterion was checked and no live media was found, which is the evidence behind a Not Applicable result.

Where there is a live stream, the result goes to a reviewer with the page and the player named, and the report records their decision and its basis.

No automated check makes a site conform. In Dreven, a person reviews the results and signs the report.

Related criteria

• 1.2.2 Captions (Prerecorded) (Level A). Recorded video needs captions too, and those are easier to check.
• 1.2.1 Audio-only and Video-only (Prerecorded) (Level A). Recordings with only sound need a transcript.
• 1.4.2 Audio Control (Level A). Audio that starts on its own must be easy to stop.

Questions people ask

All WCAG 2.2 criteria, in plain words