CSS · Performance

Unused CSS Removal

Eliminate dead CSS code with PurgeCSS, tree-shaking, and code coverage tools to reduce bundle size

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What is Unused CSS Removal?

🗑️ Dramatically reduce file size by removing unused CSS rules and selectors that aren't used in your application!

🗑️ Dead Code Elimination

Unused CSS Removal identifies and eliminates CSS rules that aren't actually used on your pages. CSS frameworks like Bootstrap or Tailwind can include hundreds of KB of unused styles. Removing them can reduce file size by 80-95%!

📉 Size Reduction

Remove unused CSS to reduce bundle size by 70-95%!

🎨 Removal Tools

PurgeCSS

Auto removal

Coverage

Find unused

UnCSS

Strip styles

Tree Shake

Build-time

🗑️

✨

Clean Code

Smaller files

Faster load

Better performance

💡

Pro Tip!

Use Chrome DevTools Coverage tab to find unused CSS instantly!

PurgeCSS Config

// 🗑️ Remove unused CSS

module.exports

= {

content: ['./src/**/*.html'],

css: ['./src/**/*.css']

}

Before & After Removal

See the dramatic difference in file size after removing unused CSS

CSS Size Comparison

Frontend

<div class="demo">
  <div class="used-only">
    <h2>This Example Uses:</h2>
    <ul>
      <li>.container</li>
      <li>.title</li>
      <li>.description</li>
      <li>.button</li>
    </ul>
  </div>
  <div class="container">
    <h1 class="title">Welcome</h1>
    <p class="description">
      This page only uses 4 CSS classes, but the full
      framework has 200+ classes included.
    </p>
    <button class="button">Click Me</button>
  </div>
  <div class="stats">
    <div class="stat">
      <span class="label">Before:</span>
      <span class="value">180 KB</span>
    </div>
    <div class="stat">
      <span class="label">After PurgeCSS:</span>
      <span class="value">8 KB</span>
    </div>
    <div class="stat success">
      <span class="label">Reduction:</span>
      <span class="value">95.5%</span>
    </div>
  </div>
</div>

Live Preview

Loading preview...

PurgeCSS Setup

Configure PurgeCSS to automatically remove unused styles

PurgeCSS Configuration

Frontend

<!-- index.html -->
<div class="app">
  <header class="header">
    <h1 class="logo">My App</h1>
    <nav class="nav">
      <a href="#" class="nav-link">Home</a>
      <a href="#" class="nav-link">About</a>
    </nav>
  </header>
  <main class="content">
    <h2 class="heading">PurgeCSS Demo</h2>
    <p class="text">
      PurgeCSS scans your HTML and removes unused CSS classes.
    </p>
    <button class="btn">Get Started</button>
  </main>
</div>
<!-- purgecss.config.js -->

Live Preview

Loading preview...

Finding Unused CSS

Use Chrome DevTools Coverage tab to identify unused styles

Manual Detection Example

Frontend

<div class="page">
  <div class="instructions">
    <h3>🔍 How to Find Unused CSS:</h3>
    <ol>
      <li>Open Chrome DevTools (F12)</li>
      <li>Press Ctrl+Shift+P (Cmd+Shift+P on Mac)</li>
      <li>Type "Coverage" and press Enter</li>
      <li>Click the reload button</li>
      <li>See unused bytes in red!</li>
    </ol>
  </div>
  <div class="example-section">
    <h2 class="section-title">Example Content</h2>
    <p class="active-class">
      This class is used and will show as green in Coverage.
    </p>
    <button class="primary-btn">Active Button</button>
  </div>
  <div class="coverage-info">
    <strong>Coverage Results:</strong><br>
    Total: 45 KB<br>
    Used: 12 KB (26.7%)<br>
    Unused: 33 KB (73.3%) 🔴
  </div>
</div>

Live Preview

Loading preview...

CSS Removal Best Practices

Automate with build tools: Integrate PurgeCSS into your Webpack, Vite, or PostCSS pipeline.

Safelist dynamic classes: Preserve classes added by JavaScript or frameworks with safelist configuration.

Test after removal: Always test your application after purging to ensure no required styles were removed.

Run in production only: Keep full CSS in development for faster rebuilds, purge only for production builds.

Build-Time ToolCSS removal happens at build time, so it works with all browsers. The resulting smaller CSS files load faster everywhere with no compatibility issues.

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CSS · Performance

Unused CSS Removal

Eliminate dead CSS code with PurgeCSS, tree-shaking, and code coverage tools to reduce bundle size

Find videos you like?

Save to resource drawer for future reference!

What is Unused CSS Removal?

🗑️ Dramatically reduce file size by removing unused CSS rules and selectors that aren't used in your application!

🗑️ Dead Code Elimination

📉 Size Reduction

Remove unused CSS to reduce bundle size by 70-95%!

🎨 Removal Tools

PurgeCSS

Auto removal

Coverage

Find unused

UnCSS

Strip styles

Tree Shake

Build-time

🗑️

✨

Clean Code

Smaller files

Faster load

Better performance

💡

Pro Tip!

Use Chrome DevTools Coverage tab to find unused CSS instantly!

PurgeCSS Config

// 🗑️ Remove unused CSS

module.exports

= {

content: ['./src/**/*.html'],

css: ['./src/**/*.css']

}

Before & After Removal

See the dramatic difference in file size after removing unused CSS

CSS Size Comparison

Frontend

<div class="demo">
  <div class="used-only">
    <h2>This Example Uses:</h2>
    <ul>
      <li>.container</li>
      <li>.title</li>
      <li>.description</li>
      <li>.button</li>
    </ul>
  </div>
  <div class="container">
    <h1 class="title">Welcome</h1>
    <p class="description">
      This page only uses 4 CSS classes, but the full
      framework has 200+ classes included.
    </p>
    <button class="button">Click Me</button>
  </div>
  <div class="stats">
    <div class="stat">
      <span class="label">Before:</span>
      <span class="value">180 KB</span>
    </div>
    <div class="stat">
      <span class="label">After PurgeCSS:</span>
      <span class="value">8 KB</span>
    </div>
    <div class="stat success">
      <span class="label">Reduction:</span>
      <span class="value">95.5%</span>
    </div>
  </div>
</div>

Live Preview

Loading preview...

PurgeCSS Setup

Configure PurgeCSS to automatically remove unused styles

PurgeCSS Configuration

Frontend

<!-- index.html -->
<div class="app">
  <header class="header">
    <h1 class="logo">My App</h1>
    <nav class="nav">
      <a href="#" class="nav-link">Home</a>
      <a href="#" class="nav-link">About</a>
    </nav>
  </header>
  <main class="content">
    <h2 class="heading">PurgeCSS Demo</h2>
    <p class="text">
      PurgeCSS scans your HTML and removes unused CSS classes.
    </p>
    <button class="btn">Get Started</button>
  </main>
</div>
<!-- purgecss.config.js -->

Live Preview

Loading preview...

Finding Unused CSS

Use Chrome DevTools Coverage tab to identify unused styles

Manual Detection Example

Frontend

<div class="page">
  <div class="instructions">
    <h3>🔍 How to Find Unused CSS:</h3>
    <ol>
      <li>Open Chrome DevTools (F12)</li>
      <li>Press Ctrl+Shift+P (Cmd+Shift+P on Mac)</li>
      <li>Type "Coverage" and press Enter</li>
      <li>Click the reload button</li>
      <li>See unused bytes in red!</li>
    </ol>
  </div>
  <div class="example-section">
    <h2 class="section-title">Example Content</h2>
    <p class="active-class">
      This class is used and will show as green in Coverage.
    </p>
    <button class="primary-btn">Active Button</button>
  </div>
  <div class="coverage-info">
    <strong>Coverage Results:</strong><br>
    Total: 45 KB<br>
    Used: 12 KB (26.7%)<br>
    Unused: 33 KB (73.3%) 🔴
  </div>
</div>

Live Preview

Loading preview...

CSS Removal Best Practices

Automate with build tools: Integrate PurgeCSS into your Webpack, Vite, or PostCSS pipeline.

Safelist dynamic classes: Preserve classes added by JavaScript or frameworks with safelist configuration.

Test after removal: Always test your application after purging to ensure no required styles were removed.

Run in production only: Keep full CSS in development for faster rebuilds, purge only for production builds.

Build-Time ToolCSS removal happens at build time, so it works with all browsers. The resulting smaller CSS files load faster everywhere with no compatibility issues.

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Loading Strategies

Minification

Building Your Learning Module...

Unused CSS Removal

🗑️ Dead Code Elimination

🎨 Removal Tools

CSS Size Comparison

PurgeCSS Configuration

Manual Detection Example

Loading Strategies

Minification

Unused CSS Removal

🗑️ Dead Code Elimination

🎨 Removal Tools

CSS Size Comparison

PurgeCSS Configuration

Manual Detection Example