<audio>
and <video>
tags without Javascript.video/webm
<video preload="auto" controls="controls" autoplay="autoplay">
<source src="https://upload.wikimedia.org/wikipedia/commons/transcoded/f/f1/Sintel_movie_4K.webm/Sintel_movie_4K.webm.720p.webm" type='video/webm'>
</video>
HTMLMediaElement.canPlayType('video/webm')
→ MediaSource.isTypeSupported('video/webm')
→