CSS - aspect ratio

.container {
  width: 100%;
  padding-top: 100%;    /* 1:1 Aspect Ratio */
  padding-top: 75%;     /* 4:3 Aspect Ratio */
  padding-top: 56.25%;  /* 16:9 Aspect Ratio */
}

.video {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

.video {
  aspect-ratio: 16 / 9;
}