Resize images and videos to fill their parent and maintain their aspect ratio with pure CSS.

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
  </head>

  <body>
    <img src="https://placeimg.com/640/425/any">
  </body>

</html>

img {
  width: 90vw;
  height: 75vh;
  border: 3px solid tomato;
  object-fit: cover;
  object-position: 20px 10px;
}


/* Demo styles only */
* {
  box-sizing: border-box;
}

body {
  margin: 0;
}