Identifies scripts and stylesheets that can block page rendering.
Render-blocking resources are files (typically CSS and JavaScript) that the browser must download, parse, and execute before it can render any of the visible page content.
If these files are large or slow to load, they create a bottleneck that leaves the user looking at a blank white screen for a long time, even if the rest of the page is ready.
This is a primary cause of a slow First Contentful Paint (FCP) and a poor user experience. It's a critical performance issue to address.
<!-- This script will block rendering -->
<script src="large-blocking-script.js"></script>
<!-- Deferring the script prevents it from blocking -->
<script src="non-blocking-script.js" defer></script>
<!-- Async also works for independent scripts -->
<script src="analytics.js" async></script>Run a free audit to see how your site performs on Render-Blocking Resources and 159 other checks.
Start Free AuditChecks if images use responsive techniques like srcset.
Checks if images have width and height attributes to prevent layout shift.
Checks for JavaScript errors in the browser console. (Note: In-dev check)
Measures the total size of the HTML document.