Performancewarning

Render-blocking resources

What this check looks for

Checks for CSS and synchronous JavaScript in the <head> that block the browser from rendering the page until they finish downloading and executing.

Why it matters

Render-blocking files delay First Contentful Paint and Largest Contentful Paint because the browser can't show anything until they load, which slows the page for real users and drags down Core Web Vitals. Deferring non-critical JavaScript, inlining critical CSS, and lazy-loading the rest lets the page paint sooner. Faster paints improve both perceived speed and the field metrics Google measures.

How to fix it

html

<!-- Defer non-critical JS so it doesn't block parsing -->
<script src="/app.js" defer></script>

<!-- Load non-critical CSS without blocking render -->
<link rel="preload" href="/non-critical.css" as="style" onload="this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="/non-critical.css"></noscript>

Go deeper

Check your site for this and 120+ other issues

Analyze any URL free