# Vercel React Best Practices > React and Next.js performance optimization guide with 57 rules across 8 categories, prioritized by impact. Use when writing, reviewing, or refactoring React/Next.js code. Use when this capability is needed. - Skill: `tomevault-io/vercel-react-best-practices-23` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/vercel-react-best-practices-23` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/vercel-react-best-practices-23/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/vercel-react-best-practices-23 --- # Vercel React Best Practices Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 57 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation. ## When to Apply Reference these guidelines when: * 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- | ## Quick Reference ### 1. Eliminating Waterfalls (CRITICAL) * `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-serialization` - Minimize data passed to client components * `server-parallel-fetching` - Restructure components to parallelize fetches * `server-after-nonblocking` - Use after() for non-blocking operations ### 4. Client-Side Data Fetching (MEDIUM-HIGH) * `client-swr-dedup` - Use SWR for automatic request deduplication * `client-event-listeners` - Deduplicate global event listeners * `client-passive-event-listeners` - Use passive listeners for scroll * `client-localstorage-schema` - Version and minimize localStorage data ### 5. Re-render Optimization (MEDIUM) * `rerender-defer-reads` - Don't subscribe to state only used in callbacks * `rerender-memo` - Extract expensive work into memoized components * `rerender-memo-with-default-value` - Hoist default non-primitive props * `rerender-dependencies` - Use primitive dependencies in effects * `rerender-derived-state` - Subscribe to derived booleans, not raw values * `rerender-derived-state-no-effect` - Derive state during render, not effects * `rerender-functional-setstate` - Use functional setState for stable callbacks * `rerender-lazy-state-init` - Pass function to useState for expensive values * `rerender-simple-expression-in-memo` - Avoid memo for simple primitives * `rerender-move-effect-to-event` - Put interaction logic in event handlers * `rerender-transitions` - Use startTransition for non-urgent updates * `rerender-use-ref-transient-values` - Use refs for transient frequent values ### 6. Rendering Performance (MEDIUM) * `rendering-animate-svg-wrapper` - Animate div wrapper, not SVG element * `rendering-content-visibility` - Use content-visibility for long lists * `rendering-hoist-jsx` - Extract static JSX outside components * `rendering-svg-precision` - Reduce SVG coordinate precision * `rendering-hydration-no-flicker` - Use inline script for client-only data * `rendering-hydration-suppress-warning` - Suppress expected mismatches * `rendering-activity` - Use Activity component for show/hide * `rendering-conditional-render` - Use ternary, not && for conditionals * `rendering-usetransition-loading` - Prefer useTransition for loading state ### 7. JavaScript Performance (LOW-MEDIUM) * `js-batch-dom-css` - Group CSS changes via classes or cssText * `js-index-maps` - Build Map for repeated lookups * `js-cache-property-access` - Cache object properties in loops * `js-cache-function-results` - Cache function results in module-level Map * `js-cache-storage` - Cache localStorage/sessionStorage reads * `js-combine-iterations` - Combine multiple filter/map into one loop * `js-length-check-first` - Check array length before expensive comparison * `js-early-exit` - Return early from functions * `js-hoist-regexp` - Hoist RegExp creation outside loops * `js-min-max-loop` - Use loop for min/max instead of sort * `js-set-map-lookups` - Use Set/Map for O(1) lookups * `js-tosorted-immutable` - Use toSorted() for immutability ### 8. Advanced Patterns (LOW) * `advanced-event-handler-refs` - Store event handlers in refs * `advanced-init-once` - Initialize app once per app load * `advanced-use-latest` - useLatest for stable callback refs --- > Source: [xxxxxccc/devops-bot](https://github.com/xxxxxccc/devops-bot) — distributed by [TomeVault](https://tomevault.io).