Render-Blocking Resources Checker
Find the scripts and stylesheets that delay first paint — the classic PageSpeed complaint, explained.
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About this tool
“Eliminate render-blocking resources” is PageSpeed’s most common complaint — this tool shows you exactly which files cause it. It fetches your page and flags every blocking script (no defer/async) and stylesheet in the head, plus missing font preloads, with the specific one-line fix for each resource.
How to use the Render-Blocking Resources Checker
- Enter the page URL.
- Review the list of blocking scripts and styles.
- Apply the suggested attribute (defer, async, media, preload) to each.
Frequently asked questions
defer or async — which should I use?
defer for scripts that need the DOM or each other (keeps order); async for independent scripts like analytics. Both stop the render blocking.
Can CSS ever be non-blocking?
Yes — split non-critical CSS with media attributes (e.g. media="print") or inline the critical part and load the rest asynchronously.