Critical CSS
Critical CSS is the subset of styles needed to render the visible part of a page, inlined into the document.
Why it matters
It removes the render-blocking stylesheet request, which is worth roughly 200ms of LCP on a cold mobile connection.
How it is measured
Check that the head contains a style element and no stylesheet link.
Checks that involve critical css
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Questions
What is critical css?
Critical CSS is the subset of styles needed to render the visible part of a page, inlined into the document.
Why does critical css matter?
It removes the render-blocking stylesheet request, which is worth roughly 200ms of LCP on a cold mobile connection.
How is critical css measured?
Check that the head contains a style element and no stylesheet link.