Vercel React Best Practices

Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 64 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

Rule Categories by Priority

References

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• references/eliminating-waterfalls.md — parallelize independent async work (Promise.all, better-all), defer await into the branch that needs it, stream with Suspense, and start promises early in API routes/Server Actions · read when touching async data flow, await chains, API routes, or Server Actions.
• references/bundle-size.md — import directly (no barrel files), next/dynamic for heavy components, defer third-party scripts past hydration, load modules conditionally, and preload on user intent · read when reducing bundle size, code-splitting, or adding third-party/analytics scripts.
• references/server-performance.md — authenticate server actions, dedupe with React.cache()/LRU, hoist static I/O, parallelize fetches, minimize RSC prop serialization, and use after() for non-blocking work · read when writing Server Components, Server Actions, or RSC data fetching.
• references/client-data-fetching.md — SWR request deduplication, shared/passive global event listeners, and versioned, minimal localStorage · read when fetching on the client, attaching window/document listeners, or persisting to storage.
• references/rerender-optimization.md — subscribe narrowly (defer reads, derived booleans), derive state during render not effects, functional/lazy useState, React.memo correctly, split hooks, transitions/useDeferredValue, and refs for transient values · read when diagnosing or preventing unnecessary re-renders and effect churn.
• references/rendering-performance.md — hoist static JSX, content-visibility/Activity for offscreen work, animate wrappers not SVGs, SVG precision, explicit conditional rendering, hydration without flicker, and resource/script hints · read when optimizing render cost, hydration flicker, SVG/animation, or <script>/preload tags.
• references/javascript-performance.md — index maps and Set/Map O(1) lookups, cached property/function/storage reads, single-pass iteration (flatMap, combined loops), early exits, hoisted RegExp, loop-based min/max, and toSorted · read when optimizing hot loops or data-structure-heavy JS.
• references/advanced-patterns.md — store event handlers in refs, initialize once per app load, and useLatest/useEffectEvent for stable callback refs · read when stabilizing callback identity or guarding one-time initialization.