React Performance provides performance optimization patterns for React 18/19 and Next.js adapted from Vercel Engineering's React Best Practices. It organizes 70+ rules across eight priority categories including waterfalls, bundle size, server-side performance, client data fetching, re-render optimization, rendering performance, JavaScript micro-performance, and advanced patterns. Use this skill when writing, reviewing, or refactoring React and Next.js code to diagnose slow page loads, remove network waterfalls, audit bundle sizes, and eliminate unnecessary re-renders.