v1.0.0 to v1.0.0

57 added, 86 removed. Audit A to A.

---

- name: vercel-react-best-practices

- description: React and Next.js performance optimization guidelines from Vercel Engineering. This skill should be used when writing, reviewing, or refactoring React/Next.js code to ensure optimal performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements.

+ name: react-native-skills

+ description: React Native and Expo best practices for building performant mobile apps. Use when building React Native components, optimizing list performance, implementing animations, or working with native modules. Triggers on tasks involving React Native, Expo, mobile performance, or native platform APIs.

license: MIT

metadata:

author: vercel

version: "1.0.0"

---

- # Vercel React Best Practices

+ # React Native Skills

- 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.

+ Comprehensive best practices for React Native and Expo applications. Contains rules across multiple categories covering performance, animations, UI patterns, and platform-specific optimizations.

## 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

+ - Building React Native or Expo apps

+ - Optimizing list and scroll performance

+ - Implementing animations with Reanimated

+ - Working with images and media

+ - Configuring native modules or fonts

+ - Structuring monorepo projects with native dependencies

## Rule Categories by Priority

|----------|----------|--------|--------|

- | 7 | JavaScript Performance | LOW-MEDIUM | `js-` |

- | 8 | Advanced Patterns | LOW | `advanced-` |

+ | 3 | UI Patterns | HIGH | `ui-` |

+ | 7 | Configuration | LOW | `fonts-`, `imports-` |

## 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)

+ ### 1. List Performance (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

+ - `list-performance-virtualize` - Use FlashList for large lists

+ - `list-performance-item-memo` - Memoize list item components

+ - `list-performance-callbacks` - Stabilize callback references

+ - `list-performance-inline-objects` - Avoid inline style objects

+ - `list-performance-function-references` - Extract functions outside render

+ - `list-performance-images` - Optimize images in lists

+ - `list-performance-item-expensive` - Move expensive work outside items

- ### 3. Server-Side Performance (HIGH)

+ ### 2. Animation (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

+ - `animation-gpu-properties` - Animate only transform and opacity

+ - `animation-derived-value` - Use useDerivedValue for computed animations

+ - `animation-gesture-detector-press` - Use Gesture.Tap instead of Pressable

- ### 4. Client-Side Data Fetching (MEDIUM-HIGH)

+ ### 3. UI Patterns (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

+ - `ui-expo-image` - Use expo-image for all images

+ - `ui-image-gallery` - Use Galeria for image lightboxes

+ - `ui-pressable` - Use Pressable over TouchableOpacity

+ - `ui-safe-area-scroll` - Handle safe areas in ScrollViews

+ - `ui-scrollview-content-inset` - Use contentInset for headers

+ - `ui-menus` - Use native context menus

+ - `ui-native-modals` - Use native modals when possible

+ - `ui-measure-views` - Use onLayout, not measure()

+ - `ui-styling` - Use StyleSheet.create or Nativewind

- ### 5. Re-render Optimization (MEDIUM)

+ ### 4. State Management (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

+ - `react-state-minimize` - Minimize state subscriptions

+ - `react-state-dispatcher` - Use dispatcher pattern for callbacks

+ - `react-state-fallback` - Show fallback on first render

+ - `react-compiler-destructure-functions` - Destructure for React Compiler

+ - `react-compiler-reanimated-shared-values` - Handle shared values with compiler

- ### 6. Rendering Performance (MEDIUM)

+ ### 5. Rendering (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

+ - `rendering-text-in-text-component` - Wrap text in Text components

+ - `rendering-no-falsy-and` - Avoid falsy && for conditional rendering

- ### 7. JavaScript Performance (LOW-MEDIUM)

+ ### 6. Monorepo (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

+ - `monorepo-native-deps-in-app` - Keep native dependencies in app package

+ - `monorepo-single-dependency-versions` - Use single versions across packages

- ### 8. Advanced Patterns (LOW)

+ ### 7. Configuration (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

+ - `fonts-config-plugin` - Use config plugins for custom fonts

+ - `imports-design-system-folder` - Organize design system imports

+ - `js-hoist-intl` - Hoist Intl object creation

## How to Use

Read individual rule files for detailed explanations and code examples:

```

- rules/async-parallel.md

- rules/bundle-barrel-imports.md

+ rules/list-performance-virtualize.md

+ rules/animation-gpu-properties.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`