<body>
  <header>
    ヘッダ
  </header>
  <main>
    コンテンツ
  </main>
  <footer>
    フッタ
  </footer>
</body>

html {
  height: 100%;
}
body {
  margin: 0;
  padding: 0;
  height: 100%;
}
header {
  width: 100%;
  background: #ccdd33;
}
footer {
  position: sticky;
  top: 100vh;
  width: 100%;
  background: #44aa33;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.