react-native-expo

React Native Expo (0.76-0.82+ / SDK 52+)

Status: Production Ready Last Updated: 2025-11-22 Dependencies: Node.js 18+, Expo CLI Latest Versions: react-native@0.82, expo@~52.0.0, react@19.1

Quick Start (15 Minutes)

1. Create New Expo Project (RN 0.76+)

# Create new Expo app with React Native 0.76+
npx create-expo-app@latest my-app

cd my-app

# Install latest dependencies
npx expo install react-native@latest expo@latest

Why this matters:

• Expo SDK 52+ uses React Native 0.76+ with New Architecture enabled by default
• New Architecture is mandatory in React Native 0.82+ (cannot be disabled)
• Hermes is the only supported JavaScript engine (JSC removed from Expo Go)

2. Verify New Architecture is Enabled

# Check if New Architecture is enabled (should be true by default)
npx expo config --type introspect | grep newArchEnabled

CRITICAL:

• React Native 0.82+ requires New Architecture - legacy architecture completely removed
• If migrating from 0.75 or earlier, upgrade to 0.76-0.81 first to use the interop layer
• Never try to disable New Architecture in 0.82+ (build will fail)

3. Start Development Server

# Start Expo dev server
npx expo start

# Press 'i' for iOS simulator
# Press 'a' for Android emulator
# Press 'j' to open React Native DevTools (NOT Chrome debugger!)

CRITICAL:

• Old Chrome debugger removed in 0.79 - use React Native DevTools instead
• Metro terminal no longer streams console.log() - use DevTools Console
• Keyboard shortcuts 'a'/'i' work in CLI, not Metro terminal

Critical Breaking Changes (Dec 2024+)

🔴 New Architecture Mandatory (0.82+)

What Changed:

• 0.76-0.81: New Architecture default, legacy frozen (no new features)
• 0.82+: Legacy Architecture completely removed from codebase

Impact:

# This will FAIL in 0.82+:
# gradle.properties (Android)
newArchEnabled=false  # ❌ Ignored, build fails

# iOS
RCT_NEW_ARCH_ENABLED=0  # ❌ Ignored, build fails

Migration Path:

1. Upgrade to 0.76-0.81 first (if on 0.75 or earlier)
2. Test with New Architecture enabled
3. Fix incompatible dependencies (Redux, i18n, CodePush)
4. Then upgrade to 0.82+

🔴 propTypes Removed (React 19 / RN 0.78+)

What Changed: React 19 removed propTypes completely. No runtime validation, no warnings - silently ignored.

Before (Old Code):

import PropTypes from 'prop-types';

function MyComponent({ name, age }) {
  return <Text>{name} is {age}</Text>;
}

MyComponent.propTypes = {  // ❌ Silently ignored in React 19
  name: PropTypes.string.isRequired,
  age: PropTypes.number
};

After (Use TypeScript):

type MyComponentProps = {
  name: string;
  age?: number;
};

function MyComponent({ name, age }: MyComponentProps) {
  return <Text>{name} is {age}</Text>;
}

Migration:

# Use React 19 codemod to remove propTypes
npx @codemod/react-19 upgrade

🔴 forwardRef Deprecated (React 19)

What Changed: forwardRef no longer needed - pass ref as a regular prop.

Before (Old Code):

import { forwardRef } from 'react';

const MyInput = forwardRef((props, ref) => {  // ❌ Deprecated
  return <TextInput ref={ref} {...props} />;
});

After (React 19):

function MyInput({ ref, ...props }) {  // ✅ ref is a regular prop
  return <TextInput ref={ref} {...props} />;
}

🔴 Swift iOS Template Default (0.77+)

What Changed: New projects use Swift AppDelegate.swift instead of Objective-C AppDelegate.mm.

Old Structure:

ios/MyApp/
├── main.m              # ❌ Removed
├── AppDelegate.h       # ❌ Removed
└── AppDelegate.mm      # ❌ Removed

New Structure:

// ios/MyApp/AppDelegate.swift ✅
import UIKit
import React

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
  func application(_ application: UIApplication, ...) -> Bool {
    // App initialization
    return true
  }
}

Migration (0.76 → 0.77): When upgrading existing projects, you MUST add this line:

// Add to AppDelegate.swift during migration
import React
import ReactCoreModules

RCTAppDependencyProvider.sharedInstance()  // ⚠️ CRITICAL: Must add this!

Source: React Native 0.77 Release Notes

🔴 Metro Log Forwarding Removed (0.77+)

What Changed: Metro terminal no longer streams console.log() output.

Before (0.76):

# console.log() appeared in Metro terminal
$ npx expo start
> LOG  Hello from app!  # ✅ Appeared here

After (0.77+):

# console.log() does NOT appear in Metro terminal
$ npx expo start
# (no logs shown)  # ❌ Removed

# Workaround (temporary, will be removed):
$ npx expo start --client-logs  # Shows logs, deprecated

Solution: Use React Native DevTools Console instead (press 'j' in CLI).

Source: React Native 0.77 Release Notes

🔴 Chrome Debugger Removed (0.79+)

What Changed: Old Chrome debugger (chrome://inspect) removed. Use React Native DevTools instead.

Old Method (Removed):

# ❌ This no longer works:
# Open Dev Menu → "Debug" → Chrome DevTools opens

New Method (0.76+):

# Press 'j' in CLI or Dev Menu → "Open React Native DevTools"
# ✅ Uses Chrome DevTools Protocol (CDP)
# ✅ Reliable breakpoints, watch values, stack inspection
# ✅ JS Console (replaces Metro logs)

Limitations:

• Third-party extensions not yet supported (Redux DevTools, etc.)
• Network inspector coming in 0.83 (late 2025)

Source: React Native 0.79 Release Notes

🔴 JSC Engine Moved to Community (0.79+)

What Changed: JavaScriptCore (JSC) moved out of React Native core, Hermes is default.

Before (0.78):

• Both Hermes and JSC bundled
• JSC available in Expo Go

After (0.79+):

// If you still need JSC (rare):
{
  "dependencies": {
    "@react-native-community/javascriptcore": "^1.0.0"
  }
}

Expo Go:

• JSC completely removed from Expo Go (SDK 52+)
• Hermes only

Note: JSC will eventually be removed entirely from React Native.

🔴 Deep Imports Deprecated (0.80+)

What Changed: Importing from internal paths will break.

Before (Old Code):

// ❌ Deep imports deprecated
import Button from 'react-native/Libraries/Components/Button';
import Platform from 'react-native/Libraries/Utilities/Platform';

After:

// ✅ Import only from 'react-native'
import { Button, Platform } from 'react-native';

Source: React Native 0.80 Release Notes

New Features (Post-Dec 2024)

CSS Properties (0.77+ New Architecture Only)

React Native now supports many CSS properties previously only available on web:

1. display: contents

Makes an element "invisible" but keeps its children in the layout:

<View style={{ display: 'contents' }}>
  {/* This View disappears, but Text still renders */}
  <Text>I'm still here!</Text>
</View>

Use case: Wrapper components that shouldn't affect layout.

2. boxSizing

Control how width/height are calculated:

// Default: padding/border inside box
<View style={{
  boxSizing: 'border-box',  // Default
  width: 100,
  padding: 10,
  borderWidth: 2
  // Total width: 100 (padding/border inside)
}} />

// Content-box: padding/border outside
<View style={{
  boxSizing: 'content-box',
  width: 100,
  padding: 10,
  borderWidth: 2
  // Total width: 124 (100 + 20 padding + 4 border)
}} />

3. mixBlendMode + isolation

Blend layers like Photoshop:

<View style={{ backgroundColor: 'red' }}>
  <View style={{
    mixBlendMode: 'multiply',  // 16 modes available
    backgroundColor: 'blue'
    // Result: purple (red × blue)
  }} />
</