Critical CSS Generator Online

What RabbitLoader's Critical CSS Generator Does

Instantly extract and optimize above-the-fold CSS for your pages to boost speed and SEO performance.

Paste Page URL

Input your complete URL. The tool loads it in a headless browser.

Click Generate

Extract only the CSS used in the above-the-fold portion.

Copy or Download

Use it inline, preload it, or add to your CSS strategy.

How to Add Critical CSS to Your Website

Once you've generated your critical CSS, follow these implementation methods to improve your page loading speed.

1. Inline in the <head>

Add critical CSS directly within a style tag in your HTML head for immediate rendering:

            
<head>
  <style>
    /* Paste your critical CSS here */
    header { background: #fff; }
    .hero { padding: 2rem 1rem; }
    /* ... */
  </style>
  
  <!-- Then load your full CSS with defer -->
  <link rel="stylesheet" href="styles.css" media="print" onload="this.media='all'">
</head>
            
          

2. Using Preload

Store critical CSS in a separate file and preload it:

            
<head>
  <link rel="preload" href="critical.css" as="style" onload="this.onload=null;this.rel='stylesheet'">
  <noscript><link rel="stylesheet" href="critical.css"></noscript>
  
  <link rel="stylesheet" href="main.css" media="print" onload="this.media='all'">
</head>

3. WordPress Implementation

For WordPress sites, add to your theme's functions.php file:

            
function add_critical_css() {
  echo '<style>';
  include get_template_directory() . '/css/critical.css';
  echo '</style>';
}
add_action('wp_head', 'add_critical_css', 1);
            
          

4. Using RabbitLoader (Automated)

The easiest method is to use RabbitLoader, which automatically extracts, optimizes, and injects critical CSS on all your pages:

            
<!-- Just add the RabbitLoader script to your site -->
<script src="https://cdn.rabbitloader.com/rabbit.js" async></script>

<!-- RabbitLoader handles the rest automatically -->

Best Practices

Keep critical CSS under 14KB (compressed) to fit in the first TCP round trip
Focus on above-the-fold content styles only
Update your critical CSS when your site design changes
Use async or defer for non-critical CSS loading
Test your implementation using tools like Lighthouse or PageSpeed Insights

Frequently Asked Questions

What is critical CSS?

Critical CSS is the CSS required to style the visible part of the page (above-the-fold). Loading it early improves perceived performance.

How does this tool help?

It extracts just the necessary styles so you can inline them in your HTML for faster rendering.

Will this improve Core Web Vitals?

Yes, especially metrics like FCP (First Contentful Paint) and LCP (Largest Contentful Paint).

Can RabbitLoader do this automatically?

Yes. RabbitLoader automates this across your entire site and updates it as your content changes.