react-native-performance

name	react-native-performance
description	Deep React Native performance — FPS profiling, bundle size, TTI measurement, native threading, memory leaks, and profiling tools.
metadata	{"author":"maikotrindade","version":"2026.5.0"}

React Native Performance

Deep performance reference. Canonical home for React Native performance — covers FlatList tuning, memoization, Hermes, expo-image, FPS measurement, bundle treemap analysis, Hermes mmap, R8 Android, 16 KB page-size alignment, view flattening, native threading, JNI memory patterns, and the profiling toolchain.

For Fabric/JSI/TurboModules architectural overview, see react-native-core/features-new-architecture.md.

Core References

Topic	Description	Reference
FPS & re-renders	FPS measurement, profile-react, React Compiler (Expo SDK 54+), atomic state, Concurrent React, Reanimated worklets (v3/v4)	core-fps-rerenders
Bundle size	App size and JS bundle reduction — Ruler, Emerge, source-map-explorer, Expo Atlas, tree shaking, barrel exports, R8, asset catalog, Hermes mmap, code splitting	core-bundle-size

Features

Topic	Description	Reference
Time to Interactive	TTI measurement methodology, cold-start pipeline markers, react-native-performance	features-tti
Native performance	TurboModule threading, sync vs async, view flattening, native SDKs over JS polyfills, 16 KB alignment, platform setup	features-native-performance
Memory	JS leak detection, native reference cycles, JNI refs, smart pointers, common leak patterns	features-memory

Best Practices

Topic	Description	Reference
Profiling tools	DevTools flamegraph, Flashlight, Xcode Instruments, Android Studio Profiler, Perfetto, bundle analyzers	best-practices-profiling

Key Recommendations

• Always measure first — never optimize without a baseline (Flashlight for FPS/TTI, source-map-explorer for bundle)
• Hermes mmap removed in RN 0.79+ — JS bundle is now resident memory; bundle size affects startup memory directly
• TurboModules — prefer sync methods for fast operations; async only when work crosses threads
• React Compiler is opt-in via Expo SDK 54+ (experiments.reactCompiler: true) — replaces most useMemo/useCallback
• Profile before refactoring — 80% of perf wins come from removing waterfalls, expensive renders, and bundle bloat, not micro-optimizations
• Reanimated v3 stable; v4 opt-in/beta — pick one per project, don't mix