native-modules

Creating a custom native module bridges JavaScript to native code by writing platform-specific implementations in Swift/Objective-C (iOS) or Kotlin/Java (Android), then exposing methods to JavaScript via callbacks or promises. Start with a simple module that exposes a single method, wire it through the native bridge, and test from JavaScript.

JSI (JavaScript Interface) provides direct synchronous access to native code; Turbo Modules modernize the bridge with type-safe codegen; Fabric is the new render engine for UI components. Turbo Modules and Fabric represent React Native's new architecture, offering better performance and developer experience than the legacy bridge.

Autolinking automatically discovers and links native dependencies without manual configuration. It works with most third-party native libraries and is the recommended approach; manual linking is only necessary for libraries predating autolinking or when autolinking fails.

Debugging native modules involves attaching native debuggers (Xcode for iOS, Android Studio for Android) while your React Native app runs, setting breakpoints in native code, and using console logging to trace execution. Use React Native's native debugging tools alongside JavaScript debugging for full visibility.

Yes, React Native enables integration with existing native SDKs by wrapping their functionality in custom native modules. This approach lets you reuse battle-tested libraries and access platform-specific features unavailable through JavaScript alone.

Expo supports native modules through Expo modules API and custom development clients, though bare React Native provides more direct native control. For Expo projects, use Expo modules or eject to a bare workflow to build custom native modules.