iframe[src*="youtube.com" i],
  iframe[src*="youtube-nocookie.com" i] {

    width: 100%;
    aspect-ratio: 16 / 9;
  }

  .portrait iframe[src*="youtube.com" i],
  .portrait iframe[src*="youtube-nocookie.com" i],
  iframe.portrait[src*="youtube.com" i],
  iframe.portrait[src*="youtube-nocookie.com" i] {

    aspect-ratio: 9 / 16;
  }