Key Takeaways
Critical CSS techniques that enable above-the-fold content to load instantly. Deliver visible content to your users in milliseconds.
What is Critical CSS?
Critical CSS is the determination of the CSS rules required for the first area of a web page that the user sees when they open the page, called above-the-fold, and presented inline in HTML. This technique allows the browser to paint the page without waiting for external CSS files.
Solving the Render Blocking Problem
Browsers, by default, wait for page painting until all CSS files have been downloaded. This causes serious delays, especially in projects with large CSS files. We eliminate this waiting with the critical CSS technique:
- Determine the CSS rules required for the top of the page.
- Add these rules inline in the
part of the HTML. - Create the main CSS file asynchronously with
media="print" onload="this.media='all'"install it.
Tools
Critical (npm package), Penthouse, and PurgeCSS help you automate this process. You can integrate it into your Laravel Mix or Vite pipeline.
Profits
- 40-60% decrease in First Contentful Paint (FCP) time.
- User instantly feels that the site is loading.
- 10-20 point increase in Lighthouse performance scores.
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