Optimizing Next.js App Router for Core Web Vitals — A Practical Guide

Short summary

Next.js App Router requires updated Core Web Vitals optimization patterns. Boost LCP through image prioritization, CDN preconnection, and responsive sizing. Prevent CLS with dimensionally-matched Suspense fallbacks and font preloading; improve INP by deferring heavy computations and code-splitting large components. Measure results with PageSpeed Insights field data, not simulated Lighthouse scores.

• •Prioritize hero images, preconnect CDNs, use proper sizes attributes for LCP
• •Match Suspense fallback dimensions to resolved content; preload fonts to prevent CLS
• •Defer computations, use dynamic imports, and measure with real-user data via PageSpeed Insights

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