Why it matters
Deaf and hard-of-hearing users miss everything said in a video without captions. Captions also serve anyone watching with the sound off.
How to fix it
Provide captions with <track kind="captions"> or burned-in captions from the video host.
Example
<video controls><source src="/demo.mp4"><track kind="captions" src="/demo.en.vtt" srclang="en" label="English"></video>References
More accessibility rules
void a11y reports 48 rules in this category. WCAG 2.2 AA through axe-core, plus checks axe can't do alone: visible keyboard focus, 24/44px target size on mobile, 320px reflow and disabled zoom.
link-in-text-blockLinks in text are distinguished only by colorautocomplete-validInvalid autocomplete valuemeta-viewportZooming is disabledbypassNo way to skip repeated contentaxe-otherOther axe-core accessibility violationtarget-sizeTouch target is smaller than 24×24 pxfocus-not-visibleKeyboard focus is not visiblereflow-overflowContent overflows horizontally at 320px