Medium impactPerformance
Render-Blocking Resources
CSS and JS in the <head> block rendering. Here's how to defer or inline them safely.
What it means
External CSS or JS files in the <head> block the browser from painting until they're downloaded and parsed.
Why it matters
Every blocking resource adds to LCP and First Contentful Paint. The fix usually moves CWV scores into the green.
How to fix it
- Identify blocking resources in PageSpeed Insights.
- Inline critical above-the-fold CSS.
- Add async or defer to non-critical <script> tags.
- Move tracking scripts to the end of <body>.
- Self-host fonts with font-display: swap.
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Frequently asked questions
Is async or defer better?
defer for scripts that need DOM order; async for independent scripts (analytics, ads).