Back to Top Button — Free HTML CSS JS Scroll-to-Top Snippet

<div class="page" id="page">
  <div class="hero">
    <h1>Scroll down to see the button appear</h1>
    <p>Keep scrolling — a floating button will fade in once you pass the threshold, and smooth-scroll you back to the top on click.</p>
  </div>
  <section class="block" id="s1"><h2>Section One</h2><p>Long pages benefit from a quick way back to the top instead of forcing a slow reverse scroll through everything already read.</p></section>
  <section class="block alt" id="s2"><h2>Section Two</h2><p>The button stays hidden until the user has scrolled past a threshold, so it never clutters the initial view of a short page.</p></section>
  <section class="block" id="s3"><h2>Section Three</h2><p>A smooth scroll animation on click feels more intentional than an instant jump, especially on pages with a lot of vertical distance to cover.</p></section>
  <section class="block alt" id="s4"><h2>Section Four</h2><p>Pair this with a scroll-progress indicator so returning users can tell at a glance how much of the page is left.</p></section>
  <button class="back-to-top" id="backToTop" onclick="scrollToTop()" aria-label="Back to top">
    <svg viewBox="0 0 24 24" width="20" height="20" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round"><path d="M12 19V5M5 12l7-7 7 7"/></svg>
  </button>
</div>

* { box-sizing: border-box; }
body { font-family: system-ui, sans-serif; margin: 0; }

.page { position: relative; }

.hero {
  padding: 80px 24px;
  background: linear-gradient(135deg, #6366f1, #8b5cf6);
  color: #fff;
  text-align: center;
}
.hero h1 { font-size: 24px; margin: 0 0 10px; }
.hero p { font-size: 14px; opacity: 0.9; max-width: 460px; margin: 0 auto; line-height: 1.6; }

.block { padding: 80px 24px; background: #fff; }
.block.alt { background: #f8fafc; }
.block h2 { font-size: 20px; color: #1e293b; margin: 0 0 10px; max-width: 560px; margin-inline: auto; }
.block p { font-size: 14px; color: #64748b; line-height: 1.7; max-width: 560px; margin: 0 auto; }

.back-to-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  border: none;
  background: #1e293b;
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 8px 20px rgba(15, 23, 42, 0.3);
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: opacity 0.25s ease, transform 0.25s ease, background 0.15s ease;
}
.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover { background: #6366f1; }
.back-to-top:focus-visible { outline: 2px solid #6366f1; outline-offset: 3px; }

const backToTop = document.getElementById('backToTop');
const SHOW_AFTER = 400;

window.addEventListener('scroll', () => {
  if (window.scrollY > SHOW_AFTER) {
    backToTop.classList.add('visible');
  } else {
    backToTop.classList.remove('visible');
  }
});

function scrollToTop() {
  window.scrollTo({ top: 0, behavior: 'smooth' });
}