Header And Footer

Document landmarks for top and bottom regions, composed with layout primitives.

Header and footer are document landmarks, not required layout classes. Use semantic elements by default.

Actual CSS
Main content
Footer links
<body class="app-shell">
  <header>Actual CSS</header>
  <main class="grow">Main content</main>
  <footer>Footer links</footer>
</body>

CSS

.app-shell {
  min-block-size: 100vh;
  display: flex;
  flex-direction: column;
}

Sticky header/footer behavior should be opt-in and documented only if it becomes part of the shipped layout API.