Core Web Vitals

Which lens this is. The metrics themselves — what LCP/INP/CLS measure, their thresholds, and their consequence for performance and search. The platform-scoreboard treatment — how SSGs and hosts compete on these numbers — is static-site-wiki/core-web-vitals. Deliberate dual-lens (HUB.md); this page is the canonical target for a bare [[core-web-vitals]].

Google’s standardized field metrics for real-world page experience — measured from actual Chrome users (the Chrome User Experience Report, crux, at p75 over 28 days), not lab tools.

A page passes when 75% of real users hit “good” on all three — web.dev’s rule is the 75th percentile of page loads, “segmented across mobile and desktop devices” (web-dev-vitals). INP replaced First Input Delay (FID) in March 2024.

You collect these on your own users with Google’s web-vitals JS library (the same way Chrome reports them to crux/PageSpeed Insights); crux is Google’s aggregate field view of the same numbers.

Supporting (diagnostic) metrics

Two metrics aren’t Core Web Vitals but exist to diagnose them: TTFB (Time to First Byte) and FCP (First Contentful Paint) — both “vital aspects of the loading experience… useful in diagnosing issues with LCP” (web-dev-vitals). They sit upstream of LCP in the lab: a slow TTFB (server/network) or FCP (render-blocking CSS/JS) shows why LCP is poor before crux‘s field number confirms it. This is the lab-half of the wiki’s “diagnose with lighthouse, judge with crux” chain.

Why this wiki cares

• The SEO link: Core Web Vitals are a (minor) Google ranking factor — see the report core-web-vitals-seo. This is the main channel through which page-weight and performance choices touch search visibility.
• The performance link: byte weight feeds LCP, but CWV is multifactorial (delivery, JS execution, TTFB also matter) — the nuance behind the page-weight thesis in synthesis and the landing-page-14kb minimalism case. The Web Almanac shows the execution tax directly: 90th-percentile mobile Total Blocking Time = 5,786 ms (web-almanac-page-weight-2024), and only ~70% of pages even use text compression.
• The enforcement link: CWV “good” thresholds are often encoded as milestone/score targets in a performance-budget.

Cross-wiki note

The sibling static-site-wiki also maintains a core-web-vitals page, where CWV is the yardstick for comparing static-site generators vs. CMSs (and where a “page weight is not destiny” contradiction was adjudicated by HTTP Archive field data). Same metric, two lenses: here it’s the SEO/perf consequence; there it’s the platform scoreboard.

Related

inp · crux · web-vitals · lighthouse · web-dev-vitals · core-web-vitals-seo · page-weight · performance-budget