core-web-vitals
Installation
SKILL.md
Core Web Vitals
The rule: report measurements or report that you could not measure. A performance claim with no number attached is noise, and a number you did not observe is worse than no number.
Targets
Field thresholds (what Google grades on, 75th percentile of real users):
| Metric | Good | Needs work | Poor |
|---|---|---|---|
| LCP — Largest Contentful Paint | ≤ 2.5s | 2.5–4.0s | > 4.0s |
| INP — Interaction to Next Paint | ≤ 200ms | 200–500ms | > 500ms |
| CLS — Cumulative Layout Shift | ≤ 0.1 | 0.1–0.25 | > 0.25 |
Lab numbers from Lighthouse on a dev build run hotter than field numbers. Treat a lab pass as necessary, not sufficient, and say which kind you measured.