Expo CLI & Dev Highlights Summary

Every highlight bullet from the 8 pages in this section, gathered on one page and grouped by the page it came from.

Local Development Basics

npx expo start launches Metro, prints a QR code, and keeps Fast Refresh running on save
LAN is the default and fastest path when your laptop and phone share Wi‑Fi
Tunnel reaches devices across VPNs and corporate firewalls - expect slower reloads
Press i or a in the terminal to boot the iOS Simulator or Android emulator without retyping flags
Expo Go is fastest for SDK-only modules; expo-dev-client is required once you add custom native code
--clear resets Metro cache after dependency, Babel, or SDK changes
Team package.json scripts keep host mode and client type consistent across machines

iOS Simulator & Android Emulator

Press i or a in Expo CLI to launch iOS Simulator or Android Emulator
Shift+I and Shift+A pick a specific device when the default is wrong
Android 16 (API 36) SDK is required to compile RN 0.86 - install it in Android Studio
Capture simulator screenshots with xcrun simctl and adb for visual regression baselines
Run a device matrix across phone, tablet, and OS versions before release

Physical Device Testing

Android: enable USB debugging, verify with adb devices, then npx expo run:android
iOS: trust the Mac, enable Developer Mode on iOS 16+, pair in Xcode Devices window
Wireless debugging removes the cable after the first USB pairing
Internal distribution via EAS puts QA builds on TestFlight and Play internal tracks
Physical hardware is mandatory for camera, push, haptics, and store-like performance

expo-dev-client

npx expo install expo-dev-client adds the development-build launcher and dev menu
Configure launchMode and defaultLaunchURL in app.json - requires a native rebuild
registerDevMenuItems adds team shortcuts without forking native code
npx expo start --dev-client serves JS to your custom binary, not Expo Go
Native module changes need eas build or npx expo run:* - JS still hot-reloads

React Native DevTools

Press j in Metro or choose Open DevTools from the in-app dev menu
React Components panel is the element inspector - select on device, edit props live
Performance and Network panels ship in RN 0.83+; Expo apps may still show Expo Network for some requests
RN 0.86 adds light/dark emulation via the DevTools Command Palette - no device settings change
Hermes is required - remote Chrome debugging via chrome://inspect is unsupported
DevTools launches as a bundled desktop app on macOS; browser fallback exists behind corporate firewalls

Flipper & Alternative Debuggers

Flipper is legacy for React Native JS debugging - RN DevTools replaced it from 0.76 onward
Remote Chrome debugging and chrome://inspect are unsupported on Hermes stacks
Use Xcode and Android Studio for native crashes, layout, and platform logs
RN 0.85+ allows multiple CDP clients - DevTools and VS Code extensions can coexist
Expo Go and dev-client both expose the same DevTools entry (j / dev menu)
Reach for Flipper only for unmaintained native plugins - plan migration to RN DevTools

Hot Reload vs Fast Refresh

Hot Reload is removed - Fast Refresh is the only live-reload path in RN 0.86
Fast Refresh preserves function component state when the edited file exports only components
Mixed exports (components + constants) force broader re-execution and often reset state
Use // @refresh reset to force remount when tuning mount-only effects or animations
Stale bundles after dependency changes need npx expo start --clear, not toggling reload modes
useEffect always re-runs on Fast Refresh - design effects to tolerate occasional re-execution

Expo CLI Best Practices

Default to LAN; use tunnel only when firewalls block Metro
Adopt expo-dev-client before custom native modules
Press j for React Native DevTools - not remote Chrome debugging
Clear Metro cache when Fast Refresh behaves inconsistently
Test on physical devices before every release candidate
Rebuild dev client after SDK or native dependency changes

Local Development Basics

npx expo start launches Metro, prints a QR code, and keeps Fast Refresh running on save

LAN is the default and fastest path when your laptop and phone share Wi‑Fi

Tunnel reaches devices across VPNs and corporate firewalls - expect slower reloads

Press i or a in the terminal to boot the iOS Simulator or Android emulator without retyping flags

Expo Go is fastest for SDK-only modules; expo-dev-client is required once you add custom native code

--clear resets Metro cache after dependency, Babel, or SDK changes

Team package.json scripts keep host mode and client type consistent across machines

iOS Simulator & Android Emulator

Press i or a in Expo CLI to launch iOS Simulator or Android Emulator

Shift+I and Shift+A pick a specific device when the default is wrong

Android 16 (API 36) SDK is required to compile RN 0.86 - install it in Android Studio

Capture simulator screenshots with xcrun simctl and adb for visual regression baselines

Run a device matrix across phone, tablet, and OS versions before release

Physical Device Testing

Android: enable USB debugging, verify with adb devices, then npx expo run:android

iOS: trust the Mac, enable Developer Mode on iOS 16+, pair in Xcode Devices window

Wireless debugging removes the cable after the first USB pairing

Internal distribution via EAS puts QA builds on TestFlight and Play internal tracks

Physical hardware is mandatory for camera, push, haptics, and store-like performance

expo-dev-client

npx expo install expo-dev-client adds the development-build launcher and dev menu

Configure launchMode and defaultLaunchURL in app.json - requires a native rebuild

registerDevMenuItems adds team shortcuts without forking native code

npx expo start --dev-client serves JS to your custom binary, not Expo Go

Native module changes need eas build or npx expo run:* - JS still hot-reloads

React Native DevTools

Press j in Metro or choose Open DevTools from the in-app dev menu

React Components panel is the element inspector - select on device, edit props live

Performance and Network panels ship in RN 0.83+; Expo apps may still show Expo Network for some requests

RN 0.86 adds light/dark emulation via the DevTools Command Palette - no device settings change

Hermes is required - remote Chrome debugging via chrome://inspect is unsupported

DevTools launches as a bundled desktop app on macOS; browser fallback exists behind corporate firewalls

Flipper & Alternative Debuggers

Flipper is legacy for React Native JS debugging - RN DevTools replaced it from 0.76 onward

Remote Chrome debugging and chrome://inspect are unsupported on Hermes stacks

Use Xcode and Android Studio for native crashes, layout, and platform logs

RN 0.85+ allows multiple CDP clients - DevTools and VS Code extensions can coexist

Expo Go and dev-client both expose the same DevTools entry (j / dev menu)

Reach for Flipper only for unmaintained native plugins - plan migration to RN DevTools

Hot Reload vs Fast Refresh

Hot Reload is removed - Fast Refresh is the only live-reload path in RN 0.86

Fast Refresh preserves function component state when the edited file exports only components

Mixed exports (components + constants) force broader re-execution and often reset state

Use // @refresh reset to force remount when tuning mount-only effects or animations

Stale bundles after dependency changes need npx expo start --clear, not toggling reload modes

useEffect always re-runs on Fast Refresh - design effects to tolerate occasional re-execution

Expo CLI Best Practices

Default to LAN; use tunnel only when firewalls block Metro

Adopt expo-dev-client before custom native modules

Press j for React Native DevTools - not remote Chrome debugging

Clear Metro cache when Fast Refresh behaves inconsistently

Test on physical devices before every release candidate

Rebuild dev client after SDK or native dependency changes

Expo CLI & Dev Highlights Summary

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Expo CLI & Dev Highlights Summary