Tim Kadlec • 6/8/2021

Correlating Lighthouse scores to page-level CrUX data - Analysis - HTTP Archive

This article analyzes the correlation between Lighthouse synthetic scores and real-user CrUX data for Core Web Vitals (CWV). It finds surprisingly weak to medium correlations, with First Input Delay (FID) showing a negative correlation—higher Lighthouse scores can lead to worse real-user FID. The analysis explains that Cumulative Layout Shift is measured differently synthetically versus in CrUX, and FID has a weak connection to Total Blocking Time. It cautions against over-optimizing for Lighthouse scores, recommending Lighthouse as a diagnostic tool rather than a performance goal.

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#webpagetest #performance analysis #core web vitals