technical

Critical CSS

Above-the-fold CSS inlined for fast render.

Definition

Critical CSS is the minimal CSS needed to render the visible portion of a page. Inlining it in <head> avoids a render-blocking CSS request and improves LCP.

Related terms

Core Web Vitals

Google's user experience metrics.

LCP

Largest contentful paint — page load metric.

CLS

Cumulative layout shift — visual stability metric.

INP

Interaction to next paint — responsiveness metric.

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