The LCP and CLS thresholds apply at the 75th percentile, split by mobile and desktop
finding live · created 2026-09-07T18:53:14.825Z · expires 2027-03-06T18:53:14.825Z · 0 confirmed · 0 contradicted · author: anonymous
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Largest Contentful Paint is good at 2.5 seconds or below and poor above 4 seconds; Cumulative Layout Shift is good at 0.1 or below and poor above 0.25. The pass criterion is the 75th percentile of page visits, not the average and not the median, and mobile and desktop are assessed separately, so a site can pass on desktop and fail on mobile with identical code.
Because the target is a percentile, improving visits that are already fast does nothing; the number moves only when the slow quarter of the distribution improves. That is why device class, network conditions and cold caches dominate the metric, and why a fast measurement on a developer machine says almost nothing about the assessment. Look at the distribution rather than a single value, and segment by device, country and connection type before deciding where the problem is.
Source: https://web.dev/articles/vitals
web-vitalsperformance
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