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Vercel React Best Practices

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This skill provides comprehensive best practices for optimizing React and Next.js applications, focusing on performance improvements such as reducing bundle size, streamlining server-side operations, and enhancing rendering efficiency. It offers specific rules and code examples across categories like eliminating waterfalls, bundle optimization, and re-render management, making it ideal for developers involved in building, reviewing, or refactoring React/Next.js projects. The guidelines aim to help teams implement impactful, automated improvements for faster, more efficient web applications.

npx skills add https://github.com/supercent-io/skills-template --skill vercel-react-best-practices

Vercel React Best Practices

Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 45 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-cache-react - Use React.cache() for per-request deduplication
  • server-cache-lru - Use LRU cache for cross-request caching
  • 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

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-dependencies - Use primitive dependencies in effects
  • rerender-derived-state - Subscribe to derived booleans, not raw values
  • rerender-functional-setstate - Use functional setState for stable callbacks
  • rerender-lazy-state-init - Pass function to useState for expensive values
  • rerender-transitions - Use startTransition for non-urgent updates

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-activity - Use Activity component for show/hide
  • rendering-conditional-render - Use ternary, not && for conditionals

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-use-latest - useLatest for stable callback refs

How to Use

For detailed explanations and code examples, read the full compiled document: AGENTS.md Each rule contains:

  • Brief explanation of why it matters
  • Incorrect code example with explanation
  • Correct code example with explanation
  • Additional context and references

Key Examples

Promise.all for Independent Operations (CRITICAL)

// ❌ Sequential: 3 round trips
const user = await fetchUser()
const posts = await fetchPosts()
const comments = await fetchComments()
// ✅ Parallel: 1 round trip
const [user, posts, comments] = await Promise.all([
  fetchUser(),
  fetchPosts(),
  fetchComments()
])

Avoid Barrel File Imports (CRITICAL)

// ❌ Imports entire library (200-800ms import cost)
import { Check, X, Menu } from 'lucide-react'
// ✅ Imports only what you need
import Check from 'lucide-react/dist/esm/icons/check'
import X from 'lucide-react/dist/esm/icons/x'

Dynamic Imports for Heavy Components (CRITICAL)

// ❌ Monaco bundles with main chunk ~300KB
import { MonacoEditor } from './monaco-editor'
// ✅ Monaco loads on demand
import dynamic from 'next/dynamic'
const MonacoEditor = dynamic(
  () => import('./monaco-editor').then(m => m.MonacoEditor),
  { ssr: false }
)

Use Functional setState (MEDIUM)

// ❌ Requires state as dependency, stale closure risk
const addItems = useCallback((newItems) => {
  setItems([...items, ...newItems])
}, [items])
// ✅ Stable callback, no stale closures
const addItems = useCallback((newItems) => {
  setItems(curr => [...curr, ...newItems])
}, [])

Constraints

Required Rules (MUST)

  1. Eliminate waterfalls: Use Promise.all and Suspense
  2. Optimize bundles: No barrel imports, use dynamic imports
  3. RSC boundaries: Serialize only the necessary data

Prohibited Patterns (MUST NOT)

  1. Sequential await: Do not execute independent fetches sequentially
  2. Array mutations: Use toSorted() instead of sort()
  3. Inline objects in React.cache: Causes cache misses

References

Metadata

Version

  • Current Version: 1.0.0
  • Last Updated: 2026-01-22
  • Compatible Platforms: Claude, ChatGPT, Gemini
  • Original Source: vercel/agent-skills

Related Skills

Tags

#React #Next.js #performance #optimization #vercel #waterfalls #bundle-size #RSC #frontend

GitHub Owner

Owner: shuding

GitHub Links

Files

performance-optimization

state-management

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