Goal
Enable people who are deaf or hard of hearing to access live audio content in real-time.
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1.2.3 Audio Description or Media Alternative (Prerecorded)
Level A
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1.2.5 Audio Description (Prerecorded)
Level AA
Success Criterion · WCAG 1.2.4
Captions (Live)
Captions are provided for all live audio content in synchronized media.
Level AAWCAG 2.0Perceivable1.2 · Time-based Media
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What to do
Provide real-time captions for all live video content that includes audio.
Why it matters
Live events, webinars, and broadcasts are inaccessible without real-time captioning for deaf and hard of hearing viewers.
Success criterion
What WCAG 1.2.4 requires
Summarized directly from the official Understanding document so teams can quote the requirement accurately.
Captions are provided for all live audio content in synchronized media.
Intent
Why WCAG created this requirement
- Live captions provide immediate access to spoken content as it happens, not after the fact.
- Real-time captioning enables deaf and hard of hearing users to participate in live events, Q&As, and interactive broadcasts.
- Live captions must be delivered with minimal delay to maintain synchronization with the visual content.
- This criterion recognizes that live captioning may have minor errors due to the real-time nature, but accuracy should still be prioritized.
Benefits
Who gains when you pass
- People who are deaf can follow live events, webinars, and broadcasts in real-time.
- People who are hard of hearing can read captions to supplement what they partially hear.
- People in environments where audio cannot be played can still follow live content.
- Non-native speakers can read along during live presentations to improve comprehension.
- Live captions enable equal participation in interactive events like Q&A sessions and live discussions.
- Recorded versions of live events will have captions already in place (though they may need cleanup).
Why it matters
User impact when this criterion fails
Summaries drawn from the Understanding document help you socialize impact statements with product stakeholders.
Without live captions, deaf users are completely excluded from live events, webinars, company meetings, and broadcasts.
Hard of hearing users miss important real-time information and cannot participate effectively in live discussions.
Time-sensitive live announcements (emergency broadcasts, breaking news) are inaccessible without real-time captioning.
Interactive elements of live events (polls, Q&A, chat) become unusable when users cannot follow the spoken context.
Overview
All live video broadcasts with audio must have real-time captions that display the dialogue as it happens. This includes live webinars, streaming events, video conferences, live news broadcasts, and any other synchronized media delivered in real-time. Unlike prerecorded content where captions can be carefully prepared in advance, live captions require real-time captioning services (CART, AI-assisted captioning, or trained captioners) to provide immediate text output.
- Live captions should appear with minimal delay (typically 2-5 seconds) to maintain synchronization.
- Real-time captioning methods include: CART (Communication Access Realtime Translation), trained stenographers, AI-assisted captioning, and broadcast captioning systems.
- Some errors are expected in live captioning due to the real-time nature; the goal is the highest accuracy possible.
- Speaker identification is important when multiple speakers are involved.
- Plan for technical contingencies—have backup captioning options if the primary method fails.
Reference: All summaries and highlights originate from Understanding WCAG 1.2.4 and the W3C quick reference.
Fast facts
- Conformance level
- Level AA
- WCAG version introduced
- WCAG 2.0
- Principle
- Perceivable
- Guideline
- 1.2 · Time-based Media
Examples
Make success tangible for teams
Share pass/fail snapshots to coach designers, engineers, QA, and content authors.
Company all-hands meeting
Pass
A live webinar uses a professional CART service that provides real-time captions with speaker identification: "CEO JOHNSON: Our Q3 results exceeded expectations..."
Fail
A company-wide live meeting has no captioning, excluding deaf employees from important announcements.
Live product launch
Pass
A streaming product launch uses AI-assisted live captioning that displays text within 3 seconds of speech, with a human monitor correcting errors.
Fail
A live stream relies solely on auto-generated captions that produce nonsensical output for product names and technical terms.
Live news broadcast
Pass
A news channel provides real-time closed captions using professional broadcast captioners, including descriptions of breaking news graphics.
Fail
A live news stream has captions that are 30+ seconds behind, making it impossible to follow time-sensitive information.
Interactive webinar with Q&A
Pass
A training webinar has live captions for both the presenter and audience questions read aloud, enabling deaf participants to follow the full discussion.
Fail
Captions only cover the main presentation but not the Q&A portion, leaving deaf attendees unable to follow audience questions.
Evidence to keep
Document conformance decisions
Capture artifacts for VPATs, procurement reviews, and regression testing.
- Document the live captioning provider/service used for each event type.
- Keep records of captioning contracts and service level agreements.
- Create a pre-event checklist for captioning setup and testing.
- Document backup procedures for captioning failures.
- Archive recordings with corrected captions as evidence of compliance.
- Track caption accuracy metrics if available from the captioning service.
Official resources
Deep dives and supporting material
Keep these links handy when writing acceptance criteria or responding to audits.
Understanding 1.2.4
Official W3C interpretation, techniques, and intent for Captions (Live).
Quick Reference 1.2.4
Filterable list of sufficient techniques and failures.
Technique G9
Creating captions for live synchronized media.
Technique G87
Providing closed captions (applicable to live content).
CART Services Information
National Association of the Deaf resource on captioning services.
FCC Closed Captioning Requirements
FCC guidelines on broadcast captioning quality and requirements.
Implementation checklist
Capture progress and blockers
- Identify all live video content with audio (webinars, live streams, broadcasts, video conferences).
- Choose a real-time captioning method: professional CART services, trained captioners, or AI-assisted solutions.
- For high-stakes events, use professional human captioners (CART providers) for highest accuracy.
- Test the captioning setup before going live to ensure captions display correctly.
- Provide speaker identification when multiple people are speaking.
- Ensure caption display has adequate contrast and sizing for readability.
- Have a backup plan if primary captioning fails (phone-in captioner, secondary service).
- After the live event, review and correct caption errors for the archived recording.
Testing ideas
Prove conformance with evidence
- Verify captions are available when the live stream begins.
- Check that captions appear with minimal delay (within a few seconds of speech).
- Monitor caption accuracy during the live event.
- Verify speaker identification is provided when speakers change.
- Test caption visibility: contrast, font size, positioning.
- Confirm captions work across different devices and browsers.
- Test the fallback plan if primary captioning fails.
- Review archived recording to assess overall caption quality.
Related success criteria
More from Time-based Media (1.2)
WCAG 1.2.1Audio-only and Video-only (Prerecorded)Level AWCAG 1.2.2Captions (Prerecorded)Level AWCAG 1.2.3Audio Description or Media Alternative (Prerecorded)Level AWCAG 1.2.5Audio Description (Prerecorded)Level AAWCAG 1.2.6Sign Language (Prerecorded)Level AAAWCAG 1.2.7Extended Audio Description (Prerecorded)Level AAAWCAG 1.2.8Media Alternative (Prerecorded)Level AAAWCAG 1.2.9Audio-only (Live)Level AAA