Providing captions for media is essential for deaf users to follow along.
Captions should be a transcription or translation of the dialogue, sound effects, and other relevant audio information.
Media elements (<audio> and <video>) should include a <track> element with kind="captions" to provide this accessibility feature.
The only exception is that muted media does not require captions.
This is required for WCAG 1.2.2 and 1.2.3 compliance.