AppRegistry

React Native · Reference cheat sheet

📋 Overview

AppRegistry is the JS entry that registers the root component. The native host looks up the app key and runs that component. Expo / CLI templates wire this for you.

🔧 Core concepts

• AppRegistry.registerComponent(appKey, () => Root) — required entry.
• App key — must match native (AppDelegate / MainActivity / app.json name).
• runApplication — used by the native side; rarely called from app code.
• Expo — registerRootComponent from expo wraps AppRegistry.

💡 Examples

import { AppRegistry } from "react-native";
import App from "./App";
import { name as appName } from "./app.json";

AppRegistry.registerComponent(appName, () => App);

// Expo
import { registerRootComponent } from "expo";
import App from "./App";

registerRootComponent(App);

⚠️ Pitfalls

• Mismatched app name between JS and native → blank screen / redbox.
• Registering twice with different roots in the same bundle.
• Forgetting the factory () => App (passing App directly is also accepted in modern RN, but factory is the classic pattern).

🔗 Related

• basic_primitives.md — building UI
• Expo/filestructure.md — Expo entry
• Expo/config.md — app name / slug
• widget.md — alternate surfaces