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React Native Best Practices

CallstackOfficialPublished by Callstack

  • Skill
  • Guidelines
  • Software development
  • MIT
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From the author

Provides React Native performance optimization guidelines for FPS, TTI, bundle size, memory leaks, re-renders, and animations. Applies to tasks involving Hermes optimization, JS thread blocking, bridge overhead, FlashList, native modules, or debugging jank and frame drops.
— the description by Callstack

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured approach to optimizing React Native applications. It focuses on critical performance metrics including FPS, Time to Interactive (TTI), bundle size, and memory management. The guide emphasizes a data-driven workflow: Measure, Optimize, Re-measure, and Validate, ensuring that performance improvements are based on actual profiling data rather than assumptions. It covers both JavaScript-level optimizations and native-level configurations, providing actionable strategies for common bottlenecks like list rendering, re-renders, and heavy native modules.

What it does

  • Provides a standardized performance measurement and optimization workflow
  • Offers specific guidance for improving FPS and reducing UI re-renders
  • Details techniques for analyzing and reducing JavaScript bundle sizes
  • Outlines strategies for optimizing TTI and native module performance
  • Includes best practices for memory leak detection and management
  • Provides a mapping of common performance problems to specific diagnostic and fix strategies

When to use it

  • When debugging janky UI, frame drops, or slow animations
  • When investigating memory leaks in JS or native code
  • When optimizing app startup time and TTI
  • When attempting to reduce the final application bundle size
  • When profiling and tuning native modules or Turbo Modules
  • During code reviews to ensure performance-conscious implementation

Advantages

  • Promotes a rigorous, evidence-based approach to performance tuning
  • Covers the full stack from React components to native bridge and bundle configuration
  • Provides clear, priority-ordered guidelines for triage
  • Includes specific diagnostic commands for profiling and bundle analysis
  • Helps avoid common pitfalls like premature optimization or incorrect dependency usage

Usage examples

“My React Native app is dropping frames during list scrolling. How should I investigate?”
The agent will guide you to use the FPS and re-render profiling workflow, suggesting the use of react-devtools to identify slow components and recommending the replacement of ScrollView with optimized alternatives like FlashList.
“How can I reduce the size of my React Native iOS bundle?”
The agent will provide steps to analyze the bundle using source-map-explorer, identify heavy dependencies, and apply optimizations such as avoiding barrel imports and enabling native code shrinking.

Install

  1. 1 of its files are not mirrored here, so install it from its source:

    https://github.com/callstackincubator/agent-skills/tree/59e9d17446a248b21d86f078fcd0bd2d36db1ca4/skills/react-native-best-practices

Documentation by Callstack

React Native Best Practices

Overview

Performance optimization guide for React Native applications, covering JavaScript/React, Native (iOS/Android), and bundling optimizations. Based on Callstack's "Ultimate Guide to React Native Optimization".

When to Apply

Reference these guidelines when:

  • Debugging slow/janky UI or animations

  • Investigating memory leaks (JS or native)

  • Optimizing app startup time (TTI)

  • Reducing bundle or app size

  • Writing native modules (Turbo Modules)

  • Profiling React Native performance

  • Reviewing React Native code for performance

Security Notes

  • Treat shell commands in these references as local developer operations. Review them before running, prefer version-pinned tooling, and avoid piping remote scripts directly to a shell.

  • Treat third-party libraries and plugins as dependencies that still require normal supply-chain controls: pin versions, verify provenance, and update through your standard review process.

  • Treat remote chunk loading as first-party artifact delivery only. Prefer app-bundled chunks or signed CI release manifests; hosted chunks must come from trusted HTTPS origins you control and be pinned to the current app release.

Priority-Ordered Guidelines

PriorityCategoryImpactPrefix
1FPS & Re-rendersCRITICALjs-*
2Bundle SizeCRITICALbundle-*
3TTI OptimizationHIGHnative-*, bundle-*
4Native PerformanceHIGHnative-*
5Memory ManagementMEDIUM-HIGHjs-*, native-*
6AnimationsMEDIUMjs-*

Impact labels are triage hints: CRITICAL first, HIGH next, MEDIUM when evidence points there.

Quick Reference

Optimization Workflow

Follow this cycle for any performance issue: Measure → Optimize → Re-measure → Validate

  1. Measure: Capture baseline metrics before changes. For runtime issues, prefer commit timeline, re-render counts, slow components, heaviest-commit breakdown, and startup/TTI when available. Component tree depth or count are optional context, not substitutes. Do not recommend memoization, atomic state, or compiler changes without a measured render or FPS problem.

  2. Optimize: Apply the targeted fix from the relevant reference

  3. Re-measure: Run the same measurement to get updated metrics

  4. Validate: Confirm improvement (e.g., FPS 45→60, TTI 3.2s→1.8s, bundle 2.1MB→1.6MB)

If metrics did not improve, revert and try the next suggested fix.

Review Guardrails

  • Check library versions before suggesting API-specific fixes. Example: FlashList v2 deprecates estimatedItemSize, so do not flag it as missing there.

  • Do not suggest useMemo or useCallback dependency changes unless behavior is demonstrably incorrect or profiling shows wasted work tied to that value.

  • Do not report stale closures speculatively. Show the stale read path, a repro, or profiler evidence before calling it out.

  • When profiling a flow, measure the target interaction itself. Do not treat component tree depth or component count as the main performance evidence.

Critical: FPS & Re-renders

Profile first:

agent-device react-devtools status
agent-device react-devtools wait --connected
agent-device react-devtools profile start
agent-device react-devtools profile stop
agent-device react-devtools profile slow --limit 5
agent-device react-devtools profile rerenders --limit 5
agent-device react-devtools profile timeline --limit 20

Drive the target interaction with normal agent-device commands between profile start and profile stop.

Manual fallback when agent-device is unavailable: open React Native DevTools from Metro (j) or the Dev Menu, use the Profiler tab, and record the same interaction.

For release-build React component profiling, connect @callstack/inspector first so React DevTools can attach to the release app, then run the agent-device react-devtools flow above.

Common fixes:

  • Replace ScrollView with FlatList/FlashList/Legend List for long lists

  • After profiling shows cascading re-renders, use React Compiler for automatic memoization

  • After profiling shows broad store/context updates, use atomic state (Jotai/Zustand) to reduce re-renders

  • Use useDeferredValue for expensive computations

Critical: Bundle Size

Analyze bundle:

npx react-native bundle \
  --entry-file index.js \
  --bundle-output output.js \
  --platform ios \
  --sourcemap-output output.js.map \
  --dev false --minify true

npx source-map-explorer output.js --no-border-checks

Verify improvement after optimization:

# Record baseline size before changes
ls -lh output.js  # e.g., Before: 2.1 MB

# After applying fixes, re-bundle and compare
npx react-native bundle --entry-file index.js --bundle-output output.js \
  --platform ios --dev false --minify true
ls -lh output.js  # e.g., After: 1.6 MB  (24% reduction)

Common fixes:

  • Avoid barrel imports (import directly from source)

  • Remove unnecessary Intl polyfills only after checking Hermes API and method coverage

  • Evaluate tree shaking (Expo SDK 52+ experimental unused import/export removal, or Re.Pack only if already configured)

  • Enable R8 for Android native code shrinking

High: TTI Optimization

Measure TTI:

  • Use react-native-performance for markers

  • Only measure cold starts (exclude warm/hot/prewarm)

Common fixes:

  • For React Native 0.78 and earlier, disable Android JS bundle compression to enable Hermes mmap

  • Use native navigation (react-native-screens)

  • Preload commonly-used expensive screens before navigating to them

High: Native Performance

Profile native:

  • iOS: Xcode Instruments → Time Profiler

  • Android: Android Studio → CPU Profiler

Common fixes:

  • Use background threads for heavy native work

  • Prefer async over sync Turbo Module methods

  • Use C++ for cross-platform performance-critical code

References

Full documentation with code examples in references/:

JavaScript/React (js-*)
FileImpactDescription
js-lists-flatlist-flashlist.mdCRITICALReplace ScrollView with virtualized lists
js-profile-react.mdMEDIUMagent-device react-devtools profiling
js-measure-fps.mdHIGHFPS monitoring and measurement
js-memory-leaks.mdMEDIUMJS memory leak hunting
js-atomic-state.mdHIGHJotai/Zustand patterns
js-concurrent-react.mdHIGHuseDeferredValue, useTransition
js-react-compiler.mdHIGHAutomatic memoization
js-animations-reanimated.mdMEDIUMReanimated worklets
js-bottomsheet.mdHIGHBottom sheet optimization
js-uncontrolled-components.mdHIGHTextInput optimization
Native (native-*)
FileImpactDescription
native-turbo-modules.mdHIGHBuilding fast native modules
native-sdks-over-polyfills.mdHIGHNative vs JS libraries
native-measure-tti.mdHIGHTTI measurement setup
native-threading-model.mdHIGHTurbo Module threads
native-profiling.mdMEDIUMXcode/Android Studio profiling
native-platform-setup.mdMEDIUMiOS/Android tooling guide
native-view-flattening.mdMEDIUMView hierarchy debugging
native-memory-patterns.mdMEDIUMC++/Swift/Kotlin memory
native-memory-leaks.mdMEDIUMNative memory leak hunting
native-android-16kb-alignment.mdCRITICALThird-party library alignment for Google Play
Bundling (bundle-*)
FileImpactDescription
bundle-barrel-exports.mdCRITICALAvoid barrel imports
bundle-analyze-js.mdCRITICALJS bundle visualization
bundle-tree-shaking.mdHIGHDead code elimination
bundle-analyze-app.mdHIGHApp size analysis
bundle-r8-android.mdHIGHAndroid code shrinking
bundle-hermes-mmap.mdHIGHDisable bundle compression
bundle-native-assets.mdHIGHAsset catalog setup
bundle-library-size.mdMEDIUMEvaluate dependencies
bundle-code-splitting.mdMEDIUMRemote chunk loading safeguards

Problem → Skill Mapping

ProblemStart With
App feels slow/jankyjs-measure-fps.md → js-profile-react.md
Too many re-rendersjs-profile-react.md → js-react-compiler.md
Slow startup (TTI)native-measure-tti.md → bundle-analyze-js.md
Large app sizebundle-analyze-app.md → bundle-r8-android.md
Memory growingjs-memory-leaks.md or native-memory-leaks.md
Animation drops framesjs-animations-reanimated.md
Bottom sheet jank/re-rendersjs-bottomsheet.md → js-animations-reanimated.md
List scroll jankjs-lists-flatlist-flashlist.md
TextInput lagjs-uncontrolled-components.md
Native module slownative-turbo-modules.md → native-threading-model.md
Native library alignment issuenative-android-16kb-alignment.md

Attribution

Based on "The Ultimate Guide to React Native Optimization" by Callstack.

Files

references/js-react-compiler.md

title: React Compiler impact: HIGH tags: memoization, react-compiler, memo, useMemo, useCallback

Skill: React Compiler

Set up React Compiler to automatically memoize components and eliminate unnecessary re-renders.

Quick Pattern

Before (manual memoization):

const MemoizedButton = memo(({ onPress }) => <Pressable onPress={onPress} />);
const handler = useCallback(() => doSomething(), []);

After (automatic with React Compiler):

// No memo/useCallback needed - compiler handles it
const Button = ({ onPress }) => <Pressable onPress={onPress} />;
const handler = () => doSomething();

When to Use

  • Want automatic performance optimization without manual memo/useMemo/useCallback

  • Codebase follows Rules of React

  • React Native 0.76+ or Expo SDK 52+

  • Ready to remove boilerplate memoization code

Prerequisites

  • Babel-based build system

  • Code follows Rules of React

  • Check current React Native, Expo, and React Compiler release notes before copying version-specific setup

Step-by-Step Instructions

Step 1: Check Compatibility

Before enabling the compiler, verify your project is compatible:

npx react-compiler-healthcheck@latest

This checks if your app follows the Rules of React and identifies potential issues.

Step 2: Install React Compiler
Expo

Use Expo's SDK-specific path:

# SDK 54 and later: Babel is auto-configured
npx expo install babel-plugin-react-compiler@beta

# SDK 53: install runtime too
npx expo install babel-plugin-react-compiler@beta react-compiler-runtime@beta

Then enable the experiment in app config:

{
  "expo": {
    "experiments": {
      "reactCompiler": true
    }
  }
}
React Native without Expo
npm install -D babel-plugin-react-compiler@latest

For React 17 or 18 targets, also install the compiler runtime:

npm install react-compiler-runtime@latest

Prefer the setup path documented for the app's exact Expo SDK, React Native, and React versions.

Step 3: Configure Babel (React Native without Expo)

For non-Expo React Native projects, configure Babel manually and keep the compiler first in the plugin pipeline:

// babel.config.js
const ReactCompilerConfig = {
  target: '19', // Use '18' for React Native < 0.78
};

module.exports = function (api) {
  api.cache(true);
  return {
    presets: ['module:@react-native/babel-preset'],
    plugins: [
      ['babel-plugin-react-compiler', ReactCompilerConfig],
      // ... other plugins
    ],
  };
};
Step 4: Set Up ESLint (Recommended)

Use the React Hooks/Compiler lint rules that match the app's React version. For Expo, SDK 55+ includes React Compiler lint rules through eslint-config-expo; SDK 54 and earlier need eslint-plugin-react-compiler. Fix rule violations before treating a component as compiler-optimized; skipped components are safe but do not get the intended memoization.

Step 5: Verify Optimizations

Verify with agent-device react-devtools before/after render measurements. For release-build verification, connect @callstack/inspector first so React DevTools can attach. Some visual DevTools versions show compiler memoization badges, but profiler evidence is the stable signal.

Incremental Adoption

You can incrementally adopt React Compiler using two strategies:

Strategy 1: Limit to Specific Directories

Configure the Babel plugin to only run on specific files, e.g. src/path/to/dir in the following examples:

Expo (create babel.config.js with npx expo customize babel.config.js):

// babel.config.js
module.exports = function (api) {
  api.cache(true);
  return {
    presets: [
      [
        'babel-preset-expo',
        {
          'react-compiler': {
            sources: (filename) => {
              return filename.includes('src/path/to/dir');
            },
          },
        },
      ],
    ],
  };
};

React Native (without Expo):

// babel.config.js
const ReactCompilerConfig = {
  target: '19',
  sources: (filename) => {
    return filename.includes('src/path/to/dir');
  },
};

module.exports = function (api) {
  api.cache(true);
  return {
    presets: ['module:@react-native/babel-preset'],
    plugins: [['babel-plugin-react-compiler', ReactCompilerConfig]],
  };
};

After changing Babel config, restart Metro with a cleared cache.

Strategy 2: Opt Out Specific Components

Use the "use no memo" directive to skip optimization for specific components or files:

function ProblematicComponent() {
  'use no memo';

  return <Text>Will not be optimized</Text>;
}

This is useful for temporarily opting out components that cause issues. Fix the underlying problem and remove the directive once resolved.

Code Examples

React Compiler Playground

Test transformations at React Playground.

What Gets Optimized
// Components - auto-memoized
const Button = ({ onPress, label }) => (
  <Pressable onPress={onPress}>
    <Text>{label}</Text>
  </Pressable>
);

// Callbacks - auto-cached (no useCallback needed)
const handlePress = () => {
  console.log('pressed');
};

// Expensive computations - auto-cached (no useMemo needed)
const filtered = items.filter((item) => item.active);
What Breaks Compilation
// BAD: Mutating props
const BadComponent = ({ items }) => {
  items.push('new item'); // Mutation!
  return <List data={items} />;
};

// BAD: Mutating during render
const BadMutation = () => {
  const [items, setItems] = useState([]);
  items.push('new'); // Mutation during render!
  return <List data={items} />;
};

// BAD: Non-idempotent render
let counter = 0;
const BadRender = () => {
  counter++; // Side effect during render!
  return <Text>{counter}</Text>;
};

Should You Remove Manual Memoization?

Improvements are primarily automatic. You can remove instances of useCallback, useMemo, and React.memo in favor of automatic memoization once the compiler is working correctly in your project.

Note: Class components will not be optimized. Migrate to function components for full benefits.

Expo's implementation only runs on application code (not node_modules), and only when bundling for the client (disabled in server rendering).

Expected Performance Improvements

Expect the largest wins in components that currently rely on manual memoization discipline or have cascading re-renders. Already well-memoized code may show little change; keep the compiler only when profiling or maintenance cost justifies it.

Common Pitfalls

  • Not fixing ESLint errors first: When ESLint reports an error, the compiler skips that component—this is safe but means you miss optimization

  • Expecting it to fix bad patterns: Compiler optimizes good code, doesn't fix bad code

  • Forgetting shallow comparison: Like memo, compiler uses shallow comparison for objects/arrays

  • Not running healthcheck: Always run npx react-compiler-healthcheck@latest before enabling

Related Skills

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

Security

No issues found by our static scan· No issues found

A static scan is not a guarantee. Skills are third-party content: review a skill before you let an agent use it.

Attribution and licence

Published by
Callstack
Publisher
Callstack (Official)
Source
callstackincubator/agent-skills · skills/react-native-best-practices · commit 59e9d17
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
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