The three metrics that matter
LCP (Largest Contentful Paint) — good at ≤ 2.5s. Usually the hero image, headline block, or main product media.
INP (Interaction to Next Paint) — good at ≤ 200ms. Measures responsiveness after clicks and taps; FID is obsolete.
CLS (Cumulative Layout Shift) — good at ≤ 0.1. Reserve space for images, ads, and fonts so the layout does not jump.
Field data vs lab data
Google evaluates Core Web Vitals primarily with real-user (CrUX / Search Console) data at the 75th percentile.
PageSpeed Insights and Lighthouse are synthetic labs — useful for reproducing a slow path, not for declaring victory. A homepage that passes in the lab while category templates fail in the field still fails overall.
Highest-ROI fixes
LCP: preload the LCP image, compress to modern formats, reduce server TTFB, avoid late-loading heroes.
INP: cut long JavaScript tasks, defer non-critical scripts, audit third-party tags and heavy WordPress plugins.
CLS: set width/height on media, avoid inserting banners above existing content, use font-display: swap carefully.
Monitor continuously
Wire Search Console CWV reports into your release process. Pair them with scheduled Audits so lab + field history stay in one place.