--- title: "What is Render-Blocking Resources? 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Squarespace Speed Optimization ](/services/squarespace-speed-optimization) [Book a Call](/contact) [Home](/) [Resources](/resources) [Glossary](/resources/glossary) Render-Blocking Resources Interactivity & Rendering · Glossary # Render-Blocking Resources ![Matt Suffoletto](/assets/matt-CEkmAuBN.jpg)Written by [Matt Suffoletto](/resources/author/matt-suffoletto) Published June 26, 2026 ![Render-Blocking Resources](/__l5e/assets-v1/26fa4c3c-d0de-48ce-9677-420f8d76e598/gloss-hero-render-blocking-resources.png) Share [](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources&text=Render-Blocking%20Resources)[](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources)[](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources)[](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources&title=Render-Blocking%20Resources) On This Page - [TL;DR](#tldr "TL;DR") - [What is Render-Blocking Resources](#definition "What is Render-Blocking Resources") - [How It's Measured](#how-measured "How It's Measured") Share this guide [](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources&text=Render-Blocking%20Resources)[](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources)[](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources)[](https://www.reddit.com/submit?url=https%3A%2F%2Fwww.pagespeedmatters.com%2Fresources%2Fglossary%2Frender-blocking-resources&title=Render-Blocking%20Resources) Speed Audit ### Find out what's slowing your website down Enter your URL and our team will send back a free, no-strings performance analysis within 24 hours. Get my audit 100% free Results in 24h ## TL;DR Render-blocking resources are external CSS and synchronous JavaScript files in the document head that the browser must download, parse, and execute before it can render any pixels of the page. ## What is Render-Blocking Resources? Render-blocking resources are external CSS and synchronous JavaScript files in the document head that the browser must download, parse, and execute before it can render any pixels of the page. Fixing this in WordPress? See our [step-by-step guide to eliminating render-blocking resources in WordPress](/resources/guides/render-blocking-resources-wordpress), or work with us through our [done-for-you speed optimization service](/services/core-web-vitals-optimization). ## How Render-Blocking Resources is Measured Lighthouse and PageSpeed Insights identify render-blocking resources with the 'Eliminate render-blocking resources' audit. ## Related Terms [Glossary ### Critical Rendering Path (CRP) ](/resources/glossary/critical-rendering-path)[Glossary ### Critical CSS ](/resources/glossary/critical-css)[Glossary ### async vs defer ](/resources/glossary/defer-async) Sources - [web.dev: Render-blocking resources](https://web.dev/articles/render-blocking-resources) [![PageSpeed Matters](/assets/logo-DtyG_mQE.png)](/) We optimize website load times to rank higher, decrease advertising costs, and convert more often. 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