| name | react-best-practices |
| description | React and Next.js performance optimization guidelines. Use when writing, reviewing, or refactoring React or Next.js code to apply stronger performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements. |
React Best Practices
Comprehensive performance optimization guide for React and Next.js applications. Contains 58 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 usedasync-parallel - Use Promise.all() for independent operationsasync-dependencies - Use better-all for partial dependenciesasync-api-routes - Start promises early, await late in API routesasync-suspense-boundaries - Use Suspense to stream content
2. Bundle Size Optimization (CRITICAL)
bundle-barrel-imports - Import directly, avoid barrel filesbundle-dynamic-imports - Use next/dynamic for heavy componentsbundle-defer-third-party - Load analytics/logging after hydrationbundle-conditional - Load modules only when feature is activatedbundle-preload - Preload on hover/focus for perceived speed
3. Server-Side Performance (HIGH)
server-auth-actions - Authenticate server actions like API routesserver-cache-react - Use React.cache() for per-request deduplicationserver-cache-lru - Use LRU cache for cross-request cachingserver-dedup-props - Avoid duplicate serialization in RSC propsserver-hoist-static-io - Hoist static I/O (fonts, logos) to module levelserver-serialization - Minimize data passed to client componentsserver-parallel-fetching - Restructure components to parallelize fetchesserver-after-nonblocking - Use after() for non-blocking operations
4. Client-Side Data Fetching (MEDIUM-HIGH)
client-swr-dedup - Use SWR for automatic request deduplicationclient-event-listeners - Deduplicate global event listenersclient-passive-event-listeners - Use passive listeners for scrollclient-localstorage-schema - Version and minimize localStorage data
5. Re-render Optimization (MEDIUM)
rerender-defer-reads - Don't subscribe to state only used in callbacksrerender-memo - Extract expensive work into memoized componentsrerender-memo-with-default-value - Hoist default non-primitive propsrerender-dependencies - Use primitive dependencies in effectsrerender-derived-state - Subscribe to derived booleans, not raw valuesrerender-derived-state-no-effect - Derive state during render, not effectsrerender-functional-setstate - Use functional setState for stable callbacksrerender-lazy-state-init - Pass function to useState for expensive valuesrerender-simple-expression-in-memo - Avoid memo for simple primitivesrerender-move-effect-to-event - Put interaction logic in event handlersrerender-transitions - Use startTransition for non-urgent updatesrerender-use-ref-transient-values - Use refs for transient frequent values
6. Rendering Performance (MEDIUM)
rendering-animate-svg-wrapper - Animate div wrapper, not SVG elementrendering-content-visibility - Use content-visibility for long listsrendering-hoist-jsx - Extract static JSX outside componentsrendering-svg-precision - Reduce SVG coordinate precisionrendering-hydration-no-flicker - Use inline script for client-only datarendering-hydration-suppress-warning - Suppress expected mismatchesrendering-activity - Use Activity component for show/hiderendering-conditional-render - Use ternary, not && for conditionalsrendering-usetransition-loading - Prefer useTransition for loading state
7. JavaScript Performance (LOW-MEDIUM)
js-batch-dom-css - Group CSS changes via classes or cssTextjs-index-maps - Build Map for repeated lookupsjs-cache-property-access - Cache object properties in loopsjs-cache-function-results - Cache function results in module-level Mapjs-cache-storage - Cache localStorage/sessionStorage readsjs-combine-iterations - Combine multiple filter/map into one loopjs-length-check-first - Check array length before expensive comparisonjs-early-exit - Return early from functionsjs-hoist-regexp - Hoist RegExp creation outside loopsjs-min-max-loop - Use loop for min/max instead of sortjs-set-map-lookups - Use Set/Map for O(1) lookupsjs-tosorted-immutable - Use toSorted() for immutability
8. Advanced Patterns (LOW)
advanced-event-handler-refs - Store event handlers in refsadvanced-init-once - Initialize app once per app loadadvanced-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
Use the relevant files in rules/ for the expanded guide.
