Core Web Vitals

What are Core Web Vitals?

Google measures real-user performance on every site using three metrics:

• Largest Contentful Paint (LCP): time to render the largest visible element. Good: under 2.5s.
• Interaction to Next Paint (INP): latency from a user input to the next visual update. Good: under 200ms.
• Cumulative Layout Shift (CLS): how much content unexpectedly moves during load. Good: under 0.1.

These scores influence SEO rankings directly. A slow site ranks lower even for exact-match branded queries.

Why AI-built apps often fail CWV

• Unoptimized hero images shipped at full resolution
• Client-rendered landing pages that show blank until JS hydrates
• No font fallbacks, causing layout shift when web fonts load
• Shipping every animation library even if most are unused

How to measure

• PageSpeed Insights
• Chrome DevTools Lighthouse panel
• Vercel Analytics (real user data)
• Google Search Console "Core Web Vitals" report

See also

• Deploy Next.js to production