vercel-react-best-practices

Vercel React Best Practices

Performance optimization guide for React and Next.js, maintained by Vercel. 69 rules across 8 categories, prioritized by impact.

When to Apply

• Writing new React components or Next.js pages
• Implementing data fetching (client or server-side)
• Reviewing code for performance issues
• Refactoring existing React/Next.js code
• Optimizing bundle size or load times

Rule Categories by Priority

Priority	Category	Impact	Prefix
1	Eliminating Waterfalls	CRITICAL	async-
2	Bundle Size Optimization	CRITICAL	bundle-
3	Server-Side Performance	HIGH	server-
4	Client-Side Data Fetching	MEDIUM-HIGH	client-
5	Re-render Optimization	MEDIUM	rerender-
6	Rendering Performance	MEDIUM	rendering-
7	JavaScript Performance	LOW-MEDIUM	js-
8	Advanced Patterns	LOW	advanced-

1. Eliminating Waterfalls (CRITICAL)

• async-cheap-condition-before-await — Check cheap sync conditions before awaiting flags or remote values
• async-defer-await — Move await into branches where actually used
• async-parallel — Use Promise.all() for independent operations
• async-dependencies — Use better-all for partial dependencies
• async-api-routes — Start promises early, await late in API routes
• async-suspense-boundaries — Use Suspense to stream content

2. Bundle Size Optimization (CRITICAL)

• bundle-barrel-imports — Import directly, avoid barrel files
• bundle-dynamic-imports — Use next/dynamic for heavy components
• bundle-defer-third-party — Load analytics/logging after hydration
• bundle-conditional — Load modules only when feature is activated
• bundle-preload — Preload on hover/focus for perceived speed

3. Server-Side Performance (HIGH)

• server-auth-actions — Authenticate server actions like API routes
• server-cache-react — Use React.cache() for per-request deduplication
• server-cache-lru — Use LRU cache for cross-request caching
• server-dedup-props — Avoid duplicate serialization in RSC props
• server-hoist-static-io — Hoist static I/O (fonts, logos) to module level
• server-no-shared-module-state — Avoid module-level mutable request state in RSC/SSR
• server-serialization — Minimize data passed to client components
• server-parallel-fetching — Restructure components to parallelize fetches
• server-parallel-nested-fetching — Chain nested fetches per item in Promise.all
• server-after-nonblocking — Use after() for non-blocking operations