Website performance: what an audit really measures

Perceived speed is not one number. It breaks into distinct metrics — first paint, visual stability, responsiveness — which Google measures separately.

Weight in the score: 18/100
checks in this category: 27

Why it matters

A visitor who waits leaves, and slowness costs rankings. But saying the site is slow names no cause: the causes are uncompressed images, render-blocking CSS, third-party JavaScript loaded ahead of content, a font that makes text flash. The audit separates those causes so the fix is specific rather than general.

The checks that run

The list below is the audit's own, generated from its catalogue — it follows the product rather than describing it from memory.

Performant transform/opacity-based animations
No render-blocking CSS
No blocking scripts in <head>
No deprecated HTML tags detected
Stable Cumulative Layout Shift (CLS)
ETag/Last-Modified headers present
Minified JavaScript files
Images displayed with correct aspect ratio
Images with dimensions and modern formats
Optimized lazy-loaded images
Images served at appropriate resolution
Reasonable DOM nesting depth
Responsive Interaction to Next Paint (INP)
Largest Contentful Paint (LCP) within recommended time
Reasonable number of CSS files
Reasonable network request count
Page compatible with back-forward cache (bfcache)
Minimal inline styles
Reasonable total page weight
Fonts loaded efficiently
Preconnect used for external origins
Reasonable inline script size
Optimized third-party scripts
Reasonable inline SVG size
Reasonable DOM size
Fast server response time
Fast Time to First Byte (TTFB)

Check your site against these

A free scan runs these checks and those of the other 10 categories, and returns the detail of every failure with its fix.

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Website performance: what an audit really measures

Why it matters

The checks that run

Check your site against these

Other categories