Render-Blocking CSS
Large CSS files in the head blocking first paint.
Medium priority · Core Web Vitals
What it is
Synchronous, unminified CSS in the <head> blocks rendering until downloaded and parsed, delaying first paint and LCP.
Why it matters
Render-blocking CSS is a leading cause of slow first paint, especially on mobile, and drags Core Web Vitals scores down.
How to fix it
Inline critical CSS, defer or preload the rest, remove unused CSS, split bundles per route, and minify. Audit with Lighthouse coverage.
What our AI checks
Our engine flags pages with slow starts tied to CSS and recommends inlining and deferral strategies.
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