expo-constants

Access system information and app constants that remain unchanged throughout app lifetime

expo-constants

Version: 55.0.5

Provides system information that remains constant throughout the lifetime of your app. Access app configuration, device info, manifest data, and environment constants.

Installation

npx expo install expo-constants

Usage

import Constants from 'expo-constants';

// Get app information
console.log(Constants.expoConfig?.name);
console.log(Constants.expoConfig?.version);

// Get system information
console.log(Constants.systemVersion);
console.log(Constants.platform);

// Get device information
console.log(Constants.deviceName);
console.log(Constants.isDevice);

API Reference

Constants

expoConfig · ExpoConfig | null

The Expo configuration object from app.json or app.config.js

const appName = Constants.expoConfig?.name;
const version = Constants.expoConfig?.version;
const slug = Constants.expoConfig?.slug;

expoGoConfig · ExpoGoConfig | null

Configuration specific to Expo Go app

manifest · Manifest | null

The classic manifest object (legacy)

manifest2 · ExpoUpdatesManifest | null

The modern manifest format used by expo-updates

appOwnership · 'expo' | 'standalone' | 'guest' | null

Indicates the type of app ownership:

• expo: Running in Expo Go
• standalone: Production build
• guest: Guest mode
• null: Bare workflow

Device Information

deviceName · string | null

The human-readable device name (e.g., “John’s iPhone”)

isDevice · boolean

true if running on a physical device, false if simulator/emulator

platform · object

Platform-specific information:

iOS:

{
  ios: {
    platform: string;
    model: string;
    userInterfaceIdiom: 'phone' | 'tablet' | 'tv';
    systemVersion: string;
  }
}

Android:

{
  android: {
    versionCode: number;
  }
}

systemVersion · string

The OS version (e.g., “15.0” for iOS, “12” for Android API 31)

App Information

nativeAppVersion · string | null

The native app version from Info.plist (iOS) or build.gradle (Android)

Example: "1.0.0"

nativeBuildVersion · string | null

The native build number

Example: "42" (iOS) or "42" (Android)

sessionId · string

A unique ID for this app session. Changes on each app launch.

statusBarHeight · number

Height of the device status bar in pixels

installationId · string

A unique ID for this app installation

Development

debugMode · boolean

true if the app is running in debug mode

executionEnvironment · ExecutionEnvironment

The execution environment:

• ExecutionEnvironment.Bare: Bare workflow
• ExecutionEnvironment.Standalone: Production build
• ExecutionEnvironment.StoreClient: Expo Go

System Directories

systemFonts · string[]

iOS only: List of system font names available

Examples

Display App Version

import Constants from 'expo-constants';
import { Text, View } from 'react-native';

function AppVersion() {
  const version = Constants.expoConfig?.version;
  const buildNumber = Constants.nativeBuildVersion;
  
  return (
    <View>
      <Text>Version: {version}</Text>
      <Text>Build: {buildNumber}</Text>
    </View>
  );
}

Check Environment

import Constants from 'expo-constants';

const isExpoGo = Constants.appOwnership === 'expo';
const isProduction = Constants.appOwnership === 'standalone';
const isBareWorkflow = Constants.appOwnership === null;

if (isExpoGo) {
  console.log('Running in Expo Go');
} else if (isProduction) {
  console.log('Running production build');
}

Access Extra Config

app.json:

{
  "expo": {
    "name": "My App",
    "extra": {
      "apiUrl": "https://api.example.com",
      "apiKey": "abc123"
    }
  }
}

Usage:

import Constants from 'expo-constants';

const apiUrl = Constants.expoConfig?.extra?.apiUrl;
const apiKey = Constants.expoConfig?.extra?.apiKey;

fetch(`${apiUrl}/data`, {
  headers: {
    'Authorization': `Bearer ${apiKey}`
  }
});

Environment-Specific Config

app.config.js:

export default {
  expo: {
    name: 'My App',
    extra: {
      apiUrl: process.env.API_URL || 'https://api.staging.example.com'
    }
  }
};

Usage:

import Constants from 'expo-constants';

const API_URL = Constants.expoConfig?.extra?.apiUrl;

Device Detection

import Constants from 'expo-constants';
import { Platform } from 'react-native';

function getDeviceInfo() {
  return {
    isSimulator: !Constants.isDevice,
    deviceName: Constants.deviceName,
    osVersion: Constants.systemVersion,
    platform: Platform.OS,
    appVersion: Constants.expoConfig?.version
  };
}

const deviceInfo = getDeviceInfo();
console.log(deviceInfo);
// {
//   isSimulator: false,
//   deviceName: "John's iPhone",
//   osVersion: "17.0",
//   platform: "ios",
//   appVersion: "1.0.0"
// }

Debug Information Display

import Constants from 'expo-constants';
import { ScrollView, Text, View, StyleSheet } from 'react-native';

function DebugInfo() {
  if (!__DEV__) return null;
  
  return (
    <ScrollView style={styles.container}>
      <Text style={styles.title}>Debug Information</Text>
      
      <Section title="App">
        <Info label="Name" value={Constants.expoConfig?.name} />
        <Info label="Version" value={Constants.expoConfig?.version} />
        <Info label="Build" value={Constants.nativeBuildVersion} />
        <Info label="Session ID" value={Constants.sessionId} />
      </Section>
      
      <Section title="Device">
        <Info label="Device" value={Constants.deviceName} />
        <Info label="Is Device" value={Constants.isDevice} />
        <Info label="OS Version" value={Constants.systemVersion} />
      </Section>
      
      <Section title="Environment">
        <Info label="App Ownership" value={Constants.appOwnership} />
        <Info label="Debug Mode" value={Constants.debugMode} />
      </Section>
    </ScrollView>
  );
}

function Section({ title, children }) {
  return (
    <View style={styles.section}>
      <Text style={styles.sectionTitle}>{title}</Text>
      {children}
    </View>
  );
}

function Info({ label, value }) {
  return (
    <Text style={styles.info}>
      {label}: {JSON.stringify(value)}
    </Text>
  );
}

const styles = StyleSheet.create({
  container: { padding: 20 },
  title: { fontSize: 24, fontWeight: 'bold', marginBottom: 20 },
  section: { marginBottom: 20 },
  sectionTitle: { fontSize: 18, fontWeight: '600', marginBottom: 10 },
  info: { fontSize: 14, marginBottom: 5 }
});

TypeScript

import Constants, { ExecutionEnvironment } from 'expo-constants';
import type { ExpoConfig } from 'expo/config';

const config: ExpoConfig | null = Constants.expoConfig;
const env: ExecutionEnvironment = Constants.executionEnvironment;

Platform Support

Platform	Supported
iOS	✅
Android	✅
Web	✅

On web, some device-specific constants may not be available or return default values.

Resources

• Official Documentation
• GitHub Repository