<div class="aspect-ratio-169">
  <iframe width="560" height="315" src="https://www.youtube.com/embed/BIvezCVcsYs" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
</div>
.aspect-ratio-169 {
  display: block;
  position: relative;
  padding-top: 56.25%;
}

.aspect-ratio-169 iframe {
  display: block;
  width: 100%;
  height: 100%;
  position: absolute;
  top: 0;
  left: 0;
}


/* Presentational styles */

body {
  background: #efefef;
  padding: 1rem;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.