What are native modules in React Native?

Question

IT Interview Practice · Accepted Answer

**Native modules** let React Native (JavaScript) access **native platform code and features** (iOS/Android) that aren't available through JavaScript — bridging to native APIs, SDKs, or custom native functionality. They extend React Native beyond what JS alone provides.

## Why native modules exist

```text
React Native's JavaScript can't directly access every native capability. NATIVE MODULES
bridge JS to native code (Swift/Objective-C on iOS, Kotlin/Java on Android):
  → access native APIs/SDKs not exposed to JS
  → use existing native libraries
  → implement performance-critical or platform-specific functionality in native code
→ The bridge between React Native's JS and the native platform.
```

## Using native modules (mostly via libraries)

```text
→ MOST native functionality is available via EXISTING LIBRARIES (npm packages that
  include native modules): camera, geolocation, Bluetooth, payments, push notifications, etc.
  → you usually INSTALL a library rather than writing native code yourself
→ EXPO provides many native APIs without writing native code (managed modules)
→ You WRITE a custom native module only when no library exists for your need
```

## Writing a custom native module (conceptually)

```text
→ Write native code (Swift/Kotlin) exposing methods to JS
→ Register/expose it so JS can call it (via the bridge / new architecture's TurboModules)
→ Call it from JavaScript like a regular module
→ Requires native development knowledge; platform-specific implementation per OS
→ The NEW ARCHITECTURE (JSI, TurboModules, Fabric) improves native interop performance
```

## Why it matters

Understanding native modules is valuable because they're **how React Native accesses native platform capabilities** beyond what JavaScript provides, an important capability for apps needing native features, so it's useful knowledge for React Native development.

The core need — React Native's JavaScript can't directly access every native capability, so **native modules bridge JS to native code** (Swift/Objective-C, Kotlin/Java) — addresses how React Native accesses device features (camera, geolocation, Bluetooth, push notifications), uses native SDKs, and implements performance-critical or platform-specific functionality.

Understanding the **practical reality** is important: **most native functionality is available through existing libraries** (npm packages that bundle native modules) or **Expo's managed native APIs**, so you usually **install a library rather than writing native code yourself** — meaning most developers consume native modules via libraries rather than writing them, an important practical point that sets realistic expectations.

Understanding that you **write a custom native module only when no library exists** for your specific need (requiring native development knowledge and per-platform implementation) clarifies when custom native work is needed.

Knowing that the **new architecture** (JSI, TurboModules, Fabric) improves native interop performance reflects awareness of React Native's evolution.

Native modules are how React Native integrates with the native platform, important for apps with native requirements, though most needs are met by existing libraries.

Since accessing native capabilities is sometimes necessary (for device features and native integration) and native modules (mostly via libraries, occasionally custom) are React Native's mechanism for it, and since understanding how they work and that most needs are met by existing libraries is valuable for React Native development, understanding native modules is valuable, practically-relevant knowledge — the bridge enabling React Native to access native features, important for apps with native needs while clarifying that most functionality comes from existing libraries rather than custom native code, useful context for working with React Native's native capabilities.

Why native modules exist

Using native modules (mostly via libraries)

Writing a custom native module (conceptually)

Why it matters

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