revision:
When present, the audio/video will automatically start playing as soon as it can do so without stopping.
The autoplay attribute can be used on the following elements:<audio >, <video>.
<element autoplay>
Click on the play button to play a sound:
<audio style="margin-left:5vw;" controls autoplay>
<source src="../../pics/horse.wav" type="audio/wav">
<source src="../../pics/horse.mp3" type="audio/mpeg">
Your browser does not support the audio element.
</audio>
Click on the play button to play a video
<video style="margin-left:5vw;" width="400" height="200" controls autoplay>
<source src="../../pics/Wuzhen-20-10_02.mp4" type="video/mp4">
</video>