methodology / Performance / #34

Core Web Vitals from CrUX (Real User Monitoring)

#34 · Recommended · Web Quality · weighted · Performance · weight 2.7% · impl implemented · method v1.2.0

Web Quality factor

This factor is part of Web Quality — the weighted 0..100 score that sits above Web Standards. Its weight depends on what kind of site is being measured. Web Standards items take priority; this factor only enters the score once Web Standards passes.

Base weight: 0.9 applied to every site type unless overridden below
Why this weight: Real-user CrUX field data is the truer signal than lab Lighthouse.

Per-site-type overrides

Site type	Weight	Δ vs base
Personal site	0.4	-0.5

Site types not listed inherit the base weight.

Same factor, two depths.

What we measure

Lab tests measure your site once on a synthetic device. CrUX uses real Chrome user data over the last 28 days, which is what Google actually uses for rankings.

How to improve your score

Optimize the same metrics as in lab tests — LCP (largest contentful paint), INP (interaction to next paint), and CLS (cumulative layout shift). Improvements show up in CrUX over a 28-day rolling window, so changes take time to surface.

Facts

Ticket

WEBQ-34

Implementation notes

Call the CrUX API by origin, fall back to URL-level if origin data is missing.

Scoring

Scoring formulas are versioned with the methodology. The current method (v1.2.0) maps raw measurements to pass, warn, fail. Factor weights determine how much each contributes to the composite — see the methodology index for the full table.

Cited by these standards

Standards in the Standards Library whose satisfiedBy requirement tree references this factor. Each link goes to the standard's full entry — methodology, scope, and the other factors it relies on.

Core Web Vitals Performance global Google's three-metric performance bar: LCP, INP, CLS. Affects rankings and is the closest thing to a universal performance standard.
Interaction to Next Paint (INP) Performance global Replaced FID as a Core Web Vital in March 2024. Measures responsiveness across the full page lifecycle — clicks, taps, key presses — not just the first interaction. ≤200ms is the bar.

Version history

Version	Change	Date
v1.2.0	Factor introduced. Status: live. Scoring impl: implemented.	2026-04-25

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