HTML редактор

<!doctype html>
<html lang="ru">

<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>background-size</title>
  <style>
    *,
    *::before,
    *::after {
      box-sizing: border-box;
    }

html {
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    }

div {
      width: 350px;
      height: 250px;
      margin: 20px auto;
      background-image: url('/examples/images/image-03.jpg');
      border: 1px solid #eee;
      background-repeat: no-repeat;
    }

.auto {
      background-size: auto;
    }

.contain {
      background-size: contain;
    }

.cover {
      background-size: cover;
    }

.w-200 {
      background-size: 200px;
    }

.w-100 {
      background-size: 100% 100%;
    }

.w-150 {
      background-size: 100% 150px;
    }

h2 {
      text-align: center;
    }
  </style>
</head>

<body>

<h2>auto (по умолчанию)</h2>
  <div class="auto"></div>

<h2>contain</h2>
  <div class="contain"></div>

<h2>cover</h2>
  <div class="cover"></div>

</body>

</html>