vercel-react-best-practices

$npx skills add vercel-labs/agent-skills --skill vercel-react-best-practices
SKILL.md

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. Reference these guidelines when: - Writing new React components or Next.js pages

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

How to Use

Read individual rule files for detailed explanations and code examples:
rules/async-parallel.md
rules/bundle-barrel-imports.md
Each rule file contains:
  • Brief explanation of why it matters
  • Incorrect code example with explanation
  • Correct code example with explanation
  • Additional context and references

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md