Render Blocking Resources Checker
Render blocking resources checker that flags every CSS and JS file delaying first paint. See sizes, host, and recommended fix.
How to use the Render-Blocking Resources Finder
- 1Paste any URL.
- 2Click Scan — we parse the <head> for blocking resources.
- 3Review the list of blocking scripts and stylesheets.
- 4Apply the per-row fix (defer, async, media, or inline).
What you can do with the Render-Blocking Resources Finder
Find render-blocking JavaScript.
Spot synchronous <script> tags in the <head> that delay first paint.
Find render-blocking CSS.
List stylesheets the browser must download before rendering.
Get fixes for each blocking resource.
Tells you whether to add defer, async, media, or inline a critical chunk.
Diagnose slow LCP from render-blocking assets.
Render-blocking resources are one of the most common LCP killers.
Render-Blocking Resources Finder FAQs
What counts as render-blocking?+
Any <script> in the head without defer/async, and any <link rel="stylesheet"> without media or preload tricks. The browser must download and process them before painting.
Should I use defer or async?+
Use defer for most third-party scripts — it preserves order and runs after parsing. Use async only for independent scripts (analytics, ad pixels).
How do I un-block a stylesheet?+
Inline the critical CSS for above-the-fold content, then load the full stylesheet with media="print" onload swap or rel="preload".
Does the scanner store my URL?+
No. Each scan is one-shot and discarded after display.
Will fixing render-blocking really speed up my site?+
Yes — it's one of the highest-impact wins for LCP and First Contentful Paint.
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