<audio>
and <video>
tags without Javascript.video/webm
<video preload="auto" controls="controls" autoplay="autoplay">
<source src="https://upload.wikimedia.org/wikipedia/commons/transcoded/c/c0/Big_Buck_Bunny_4K.webm/Big_Buck_Bunny_4K.webm.480p.webm" type='video/webm'>
</video>
HTMLMediaElement.canPlayType('video/webm')
→ MediaSource.isTypeSupported('video/webm')
→