VercatusCWV thresholds
Core Web Vitals are assessed at the 75th percentile of page loads, segmented by mobile and desktop. Good/poor boundaries: LCP ≤ 2.5 s good, > 4 s poor; INP ≤ 200 ms good, > 500 ms poor; CLS ≤ 0.1 good, > 0.25 poor. A page passes only if it meets the good threshold at p75 on all three; a p75 in the poor band means at least a quarter of loads are poor, a problem for a real share of visitors rather than an unlucky few.
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AGrade A: official documentation or a standard. A grade describes the provenance of the sources above; it is not a probability that a change will work. The effect basis says how the size of the effect is known: measured by a study, taken from an industry report, only documented without a size, or not quantified.
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