Templates & Custom Elements

🌐 HTML5 🟢 Chapter 32 of 37 📂 Phase 12: Advanced HTML5 📅 2026 Edition

📌 Covered in this chapter: <template> Tag · Inert Content & cloneNode() · Custom Elements · Shadow DOM Overview · Custom Element Lifecycle · <slot> Projection

Welcome to Phase 12 (Chapter 32): Templates & Custom Elements! HTML standard custom elements allow developers to extend HTML vocabulary with reusable component markup.

1Template & Cloning Example

HTML — Template & Cloning Syntax ▶ Run in HTML Editor

<template id="card-template">
  <div class="card" style="border:1px solid #f97316; padding:15px; border-radius:8px;">
    <h3 class="title" style="color:#f97316;"></h3>
    <p class="desc"></p>
  </div>
</template>

<div id="output"></div>

<script>
  const temp = document.getElementById('card-template');
  const clone = temp.content.cloneNode(true);
  clone.querySelector('.title').textContent = 'HTML5 Masterclass';
  clone.querySelector('.desc').textContent = 'Learn HTML5 from scratch.';
  document.getElementById('output').appendChild(clone);
</script>

Written by Our Compiler Technical Editorial Team
Reviewed for accuracy & tested on HTML5 Standards · Last updated August 2026