Research | MIT - Massachusetts Institute of Technology

Alumni | MIT - Massachusetts Institute of Technology

Visit | MIT - Massachusetts Institute of Technology

Education | MIT - Massachusetts Institute of Technology

MIT Parents | MIT - Massachusetts Institute of Technology

About MIT | MIT - Massachusetts Institute of Technology

All pre-recorded audio and video should provide appropriate captions. This allows people who are deaf 
or hard-of-hearing to use the media. 

## Requirements
WCAG requires that captions:

* Represent all spoken dialogue
* Indicate who is speaking, when not visually obvious
* Include important non-speech sounds, like:
  * Laughter
  * Alarms
  * Music lyrics or tone (if meaningful)
  * Sound cues (e.g. _door creaks_)

## What this check looks for

This check identifies video and audio on the page, and checks whether that includes machine-readable captions.

This check will fail if:

* There is a video or audio element that is not muted, and it does not contain a caption track.
* There is a link to a known video platform (such as Vimeo) where captions are not clearly available.

## How this check works

### 1. Videos or audio using HTML5

The check scans for `<video>` and `<audio>` elements directly in the page’s HTML. For each one, it looks at:

* **Whether the media is muted**
  If the media is permanently muted using the muted attribute, the check ignores it. Muted media is assumed not to convey important information through audio.
* **Whether captions are provided**
  The check looks for a <track> element inside the media tag, which is where captions should be included. If no caption track is found, the media fails this check.

Only the first video file source is reported for each video, to avoid confusion from fallback formats.

### 2. Links to external video players

The check also looks for links to known video platforms such as Vimeo. If a link appears to go directly to a video 
and there’s no indication that captions are available, the check flags it.

## When captions aren’t needed

If the media is silent, decorative, or doesn’t include any meaningful audio content, then captions may not be 
necessary. However, in most cases where information is conveyed through audio, captions must be provided to 
meet accessibility requirements.

## Further reading

See [Understanding WCAG Success Criterion 1.2.2](https://www.w3.org/TR/UNDERSTANDING-WCAG20/media-equiv-captions.html).

prerecorded-captions-alternative

October 2025

September 2025

Massachusetts Institute of Technology

Title / URL	Issues
Research \| MIT - Massachusetts Institute of Technologyweb.mit.edu/research/	1
Alumni \| MIT - Massachusetts Institute of Technologywww.mit.edu/alumni/	1
Visit \| MIT - Massachusetts Institute of Technologyweb.mit.edu/visitmit/	1
Education \| MIT - Massachusetts Institute of Technologywww.mit.edu/education/	1
Education \| MIT - Massachusetts Institute of Technologyweb.mit.edu/education/	1
MIT Parents \| MIT - Massachusetts Institute of Technologywww.mit.edu/parents/	1
About MIT \| MIT - Massachusetts Institute of Technologyweb.mit.edu/about/	1
Visit \| MIT - Massachusetts Institute of Technologywww.mit.edu/visitmit/	1
About MIT \| MIT - Massachusetts Institute of Technologywww.mit.edu/about/	1
MIT Parents \| MIT - Massachusetts Institute of Technologyweb.mit.edu/parents/	1

Ensure captions are provided for all prerecorded audio and video

Massachusetts Institute of Technology

Where this issue has occurred