Core Web Vitals
読み方：Core Web Vitals
Google's set of user experience metrics used as a search ranking signal. Comprises LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), and INP (Interaction to Next Paint). Optimizing these metrics improves both user experience and search rankings.
What are Core Web Vitals
Core Web Vitals are three metrics Google uses to measure real-world user experience on web pages. They became a search ranking factor in 2021. Improving them benefits both users and search visibility.
The Three Metrics
### LCP (Largest Contentful Paint)
Time until the largest above-the-fold content element loads.
- • Good: ≤ 2.5 seconds
- • Needs improvement: 2.5–4.0 seconds
- • Poor: > 4.0 seconds
### CLS (Cumulative Layout Shift)
Total unexpected visual movement of page content as it loads.
- • Good: ≤ 0.1
- • Needs improvement: 0.1–0.25
- • Poor: > 0.25
### INP (Interaction to Next Paint)
Time from user interaction (click, tap, keypress) to visual response.
- • Good: ≤ 200ms
- • Needs improvement: 200–500ms
- • Poor: > 500ms
How to Measure
- • Google Search Console: Real user data from your actual visitors
- • PageSpeed Insights: Lab data + field data for any URL
- • Chrome DevTools: Local diagnosis
Quick Wins
- • LCP: Use `priority` on hero images, optimize fonts with `next/font`
- • CLS: Set explicit width/height on images, pre-reserve space for dynamic content
- • INP: Use `startTransition` for non-urgent state updates, reduce bundle size