App Config

Also called app.json, app.config.js, app.config.ts

What is App Config in React Native?

App config is the app.json or app.config.js/ts file where an Expo project declares its name, identifiers, icons, permissions and plugins for native generation.

App config is the file at the root of an Expo project, app.json or its dynamic form app.config.js / app.config.ts, that describes the app: display name, version, icon, splash screen, bundle identifier, permissions and the list of config plugins.

It matters because it is the source of truth for the native projects. With Continuous Native Generation, npx expo prebuild reads app config and writes Info.plist, AndroidManifest.xml and the rest, running each config plugin along the way. EAS Build, Expo CLI and Expo Router read it too.

The dynamic form is plain code, which helps when values depend on the build:

import { ExpoConfig, ConfigContext } from 'expo/config';

export default ({ config }: ConfigContext): ExpoConfig => ({
  ...config,
  name: process.env.APP_VARIANT === 'dev' ? 'MyApp (Dev)' : 'MyApp',
  slug: 'my-app',
});

The config argument contains whatever is in app.json, so the two files can coexist. Run npx expo config to print the fully resolved result.

Common gotchas:

Changing native fields such as permissions, icons or the bundle identifier needs a new native build. A JavaScript reload will not pick them up.
If you commit your own ios/ and android/ folders and never run prebuild, most native fields in app config are ignored, which Expo Doctor warns about.
Anything placed under extra ends up readable inside the app bundle. It is not a place for secrets.