JSFiddle - React, Tailwind, and code Playground

HTML

<div class="ytb">
<iframe width="640" height="480" src="http://www.youtube.com/embed/QKh1Rv0PlOQ?autoplay=1&controls=0&html5=true" frameborder="0"></iframe>
</div>

CSS

iframe {
    border-radius: 20px !important;
}