ACT Rule ab4d13 · proposed
Video element content is media alternative for text
Sometimes the video is the alternative. This rule checks whether it restates text already on the page in full, and whether the page says so clearly enough for a reader to tell.
A tool can find the places this applies and then hand you the decision. The rule is proposed, so it has not yet been implemented in full by a tool and reviewed by a W3C working group, and the wording can still change.
Why passing this rule settles nothing about WCAG
W3C's requirements mapping for this rule names no WCAG success criterion as a conformance requirement. That is the position of 24 of the 87 live rules and this is one of them, which is why a scanner can flag it while an auditor leaves it out of the findings. Both of them are reading the same page correctly.
Three separate composite rules use this one's answer, which is more than any other atomic rule in the set. Media alternative is an escape hatch that only works when the text really is complete, and only a person reading both can say whether it is.
The composite rules this one feeds
This is an atomic input rule, which is why it names no criterion of its own. W3C combines its outcome with the other inputs below, and it is the composite that maps to WCAG. A report that cites this rule id alone has told you about one ingredient, not about the dish.
- Video element auditory content has accessible alternative A tool finds candidates, you decide
- Video element visual content has accessible alternative A tool finds candidates, you decide
- Video element visual content has strict accessible alternative A tool finds candidates, you decide
The normative rule text lives at W3C
What the rule applies to, and exactly what it expects, is published by W3C and can change. We link to it rather than restate it, so nothing here can quietly fall out of date against the source. Read rule ab4d13 at W3C.
Transcripts, captions and audio description are not the same thing
Which alternative a piece of media needs depends on what is in it. Video with sound needs captions so a deaf viewer gets the dialogue. It also needs audio description so a blind viewer gets what is only shown on screen.
Audio on its own needs a transcript. Video with no sound needs either a transcript or an audio track. Getting one of these right does not cover the others. Several rules look at the same file and ask different questions about what it has to be.
The usual mistake is a transcript posted under a video and treated as finished. It helps, but it is not a caption. It does not meet the criterion that asks for captions.
All 87 ACT rules are grouped by the criteria they test, and 24 of them decide nothing about WCAG on their own. Run a free scan to see which of these your own pages trip.