What are Native Modules in React Native?

Native Modules allow JavaScript to call native platform code (Swift/Objective-C on iOS, Kotlin/Java on Android). Used when React Native doesn't provide a built-in API for a device feature or when you need a performance-critical native implementation. When to use native modules: accessing hardware (Bluetooth, NFC), integrating third-party SDKs (analytics, payment SDKs), CPU-intensive operations (image processing, encryption), features not yet in React Native core. Old Architecture native module (iOS — Objective-C): // MyModule.h: @interface MyModule : NSObject <RCTBridgeModule> @end // MyModule.m: @implementation MyModule RCT_EXPORT_MODULE(); RCT_EXPORT_METHOD(greet:(NSString *)name resolver:(RCTPromiseResolveBlock)resolve rejecter:(RCTPromiseRejectBlock)reject) { NSString *greeting = [NSString stringWithFormat:@"Hello, %@!", name]; resolve(greeting); } @end // JavaScript: import { NativeModules } from "react-native"; const { MyModule } = NativeModules; const greeting = await MyModule.greet("Alice");. New Architecture TurboModule: uses JSI for synchronous calls and TypeScript specifications for type safety. Community modules: thousands of pre-built native modules on npm — react-native-camera, react-native-maps, react-native-bluetooth, etc. Always check before writing your own. Expo modules API: Expo provides a cleaner API for writing native modules with Swift/Kotlin, strongly typed, works with both old and new architecture.