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CSS Loading Strategies determine how and when CSS is loaded and applied. CSS blocks rendering by default, so optimizing its delivery is crucial for fast page loads. Modern techniques include critical CSS inline, async loading, and preloading.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Critical CSS Example</title>
<!-- ⚡ CRITICAL CSS - Inline for instant render -->
<!-- 📦 NON-CRITICAL CSS - Load async -->
<link rel="preload" href="/styles.css" as="style"
onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/styles.css"></noscript>
</head>
<body>
<section class="hero">
<div>
<h1>Lightning Fast ⚡</h1>
<p>Critical CSS loads instantly</p>
<button class="cta">Get Started</button>
</div>
</section>
<section class="content">
<h2>Below the Fold Content</h2>
<p>This section's styles can load later without blocking initial render.</p>
</section>
</body>
</html>Loading preview...
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>CSS Preload Example</title>
<!-- 📝 In production, you would use: -->
<!--
<link rel="preload" href="/styles/main.css" as="style">
<link rel="stylesheet" href="/styles/main.css">
-->
</head>
<body>
<div class="demo-container">
<header>
<h1>CSS Preload Demo</h1>
<nav>
<a href="/">Home</a>
<a href="/about">About</a>
</nav>
</header>
<main>
<div class="info-box">
<h2>How Preloading Works:</h2>
<p>
Preload hints tell the browser to start downloading CSS files
early, before they're discovered in the normal parsing process.
</p>
</div>
<div class="benefit">
<strong>Benefits:</strong><br>
✓ Faster initial render<br>
✓ Better Core Web Vitals<br>
✓ Improved user experience
</div>
<div class="code-example">
<code><link rel="preload" href="main.css" as="style"></code>
<code><link rel="stylesheet" href="main.css"></code>
</div>
</main>
</div>
</body>
</html>Loading preview...
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Async CSS Loading</title>
<!-- ⚡ CRITICAL - Inline or blocking -->
<!-- 🚀 ASYNC - Non-blocking load -->
<link rel="preload"
href="/non-critical.css"
as="style"
onload="this.onload=null;this.rel='stylesheet'">
<noscript>
<link rel="stylesheet" href="/non-critical.css">
</noscript>
<!-- Alternative: Media query trick -->
<link rel="stylesheet"
href="/print.css"
media="print"
onload="this.media='all'">
</head>
<body>
<header class="header">
<h1>Async Loading Example</h1>
</header>
<main class="content">
<h2>Non-Blocking CSS</h2>
<p>
The header renders immediately with critical CSS.
Additional styles load asynchronously without blocking.
</p>
<div class="card">
<h3>Benefits</h3>
<ul>
<li>✓ Faster First Contentful Paint</li>
<li>✓ Better Largest Contentful Paint</li>
<li>✓ Improved Time to Interactive</li>
</ul>
</div>
</main>
</body>
</html>Loading preview...
<link rel="preload"> for CSS needed early but not critical.media="print" trick or JavaScript to load below-the-fold CSS asynchronously.rel="preload") is supported in all modern browsers. The async loading patterns work universally with progressive enhancement.