adb & Android Devices

Q: Why does emulator see Metro but USB phone does not?

Emulator uses 10.0.2.2 to reach host localhost - physical devices do not. Use adb reverse on USB or --host lan with correct laptop IP on Wi-Fi.

Q: How do I find the installable APK path after expo run:android?

android/app/build/outputs/apk/debug/app-debug.apk for standard debug builds. EAS artifacts download from eas build:list - see jq, rg & JSON Logs.

Q: Does adb work on iOS?

No - use xcrun simctl and Xcode devices window for Apple platforms.

adb (Android Debug Bridge) is the terminal interface to emulators and USB hardware - list devices, reverse Metro ports, tail logcat, and install dev builds without opening Android Studio. Expo SDK 57 wraps daily compiles in npx expo run:android; this page is the cookbook for when logcat, port forwarding, or APK installs need explicit control.

Recipe

Quick-reference recipe card - copy-paste ready.

# Verify toolchain + device
export ANDROID_HOME="$HOME/Library/Android/sdk"
export PATH="$PATH:$ANDROID_HOME/platform-tools"
adb devices -l
 
# USB dev: Metro port reverse (8081 default)
adb reverse tcp:8081 tcp:8081
npx expo start --dev-client
 
# RN-focused logcat
adb logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E
 
# Install dev APK (EAS internal or local debug)
adb install -r ./build/app-debug.apk
adb shell am start -n com.example.app/.MainActivity

When to reach for this:

npx expo run:android cannot see a device (no devices/emulators found).
USB hardware cannot load the JS bundle - Metro works on emulator but not phone.
You need native crash stack traces beyond the redbox.
CI or QA installs a prebuilt APK without Gradle on the laptop.
Deep link or notification cold-start must be scripted for Maestro prep.

Working Example

USB physical device: reverse Metro, install dev client, tail logs, open deep link.

#!/usr/bin/env bash
set -euo pipefail
 
PACKAGE="com.example.shopapp"
APK="./shopapp-debug.apk"   # from eas build --profile development --platform android
 
# 1. Single device guard
SERIAL=$(adb devices | awk 'NR>1 && $2=="device" {print $1; exit}')
if [[ -z "$SERIAL" ]]; then
  echo "No adb device in 'device' state. Enable USB debugging." >&2
  exit 1
fi
echo "Using device: $SERIAL"
 
# 2. Port reverse for Metro (USB)
adb -s "$SERIAL" reverse tcp:8081 tcp:8081
adb -s "$SERIAL" reverse --list
 
# 3. Install / upgrade dev client
adb -s "$SERIAL" install -r "$APK"
 
# 4. Cold start main activity
adb -s "$SERIAL" shell am force-stop "$PACKAGE"
adb -s "$SERIAL" shell am start -n "$PACKAGE/.MainActivity"
 
# 5. Deep link smoke
adb -s "$SERIAL" shell am start -a android.intent.action.VIEW \
  -d "shopapp://orders/42" "$PACKAGE"
 
# 6. Logs in second terminal - native crashes + JS console
adb -s "$SERIAL" logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E

Start Metro (separate terminal):

npx expo start --dev-client --clear

What this demonstrates:

-s SERIAL - mandatory when emulator and phone are both connected.
adb reverse - USB path to Metro without Wi-Fi IP alignment.
install -r - replaces existing debug build while keeping app data (usually).
am start -a VIEW -d - intent filter / deep link verification from bash.
Filtered logcat - surfaces ReactNativeJS and fatal AndroidRuntime errors.

Deep Dive

How It Works

adb speaks to adbd on the device/emulator over USB or TCP (wireless debugging).
Metro serves JS on localhost:8081 on your laptop - the device needs a path to that port (reverse, shared LAN IP, or tunnel).
npx expo run:android invokes Gradle installDebug then launches the app - adb install skips compile when you already have an APK.
Dev clients built with expo-dev-client still need Metro for JS - adb reverse is the USB shortcut.

Device Discovery

adb devices -l                    # serial, state, model
adb kill-server && adb start-server # reset daemon when devices flap
adb -e <cmd>                        # only emulator
adb -d <cmd>                        # only USB device

State	Meaning	Fix
`device`	Ready	Proceed
`unauthorized`	RSA key not accepted on phone	Tap "Allow USB debugging"
`offline`	Cable/driver glitch	Replug, `adb kill-server`
empty list	No emulator running	Android Studio AVD or `emulator -avd <name>`

# List AVDs and boot one (emulator binary is in ANDROID_HOME)
emulator -list-avds
emulator -avd Pixel_8_API_35 &
adb wait-for-device

Port Reverse & Forward

# Metro (default 8081)
adb reverse tcp:8081 tcp:8081
 
# DevTools or custom packager port
adb reverse tcp:8082 tcp:8082
 
# Show active reverses
adb reverse --list
 
# Remove all reverses
adb reverse --remove-all
 
# Forward device port to laptop (less common in RN)
adb forward tcp:9000 tcp:9000

Wi-Fi dev - skip reverse; use npx expo start --dev-client --host lan and ensure phone and laptop share subnet.
Corporate VPN - often breaks LAN; try --tunnel on Metro or USB reverse.

logcat Recipes

# RN daily driver
adb logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E
 
# Clear buffer before reproducing a crash
adb logcat -c && adb logcat '*:S' ReactNativeJS:V AndroidRuntime:E
 
# Save to file for CI artifact
adb logcat -d > android-logcat.txt
 
# Filter by PID after launch (adb shell pidof)
PID=$(adb shell pidof -s com.example.app)
adb logcat --pid="$PID"
 
# Kotlin/Java crash stack only
adb logcat '*:S' AndroidRuntime:E

Install & Launch

# Debug APK from expo run:android
adb install -r android/app/build/outputs/apk/debug/app-debug.apk
 
# EAS internal distribution APK
adb install -r ./downloads/shopapp.apk
 
# Uninstall clean
adb uninstall com.example.app
 
# Launch launcher activity
adb shell monkey -p com.example.app -c android.intent.category.LAUNCHER 1
 
# Force stop
adb shell am force-stop com.example.app
 
# Clear app data (logout / corrupted storage)
adb shell pm clear com.example.app

applicationId in app.config.ts (android.package) must match adb package strings.
Play-signed AAB from production eas build is not installable via adb - use internal APK/AAB track or bundletool.

Shell Utilities

# Screenshot (PNG to stdout redirected)
adb exec-out screencap -p > screen.png
 
# Screen record (max 180s on many devices)
adb shell screenrecord /sdcard/demo.mp4
adb pull /sdcard/demo.mp4
 
# Input text (ASCII only - no spaces without %s)
adb shell input text "hello"
 
# Open system settings deep link
adb shell am start -a android.settings.APPLICATION_DETAILS_SETTINGS \
  -d package:com.example.app

Bash Notes

# macOS default SDK path - align with Android Studio install
export ANDROID_HOME="$HOME/Library/Android/sdk"
export PATH="$PATH:$ANDROID_HOME/platform-tools:$ANDROID_HOME/emulator"
 
# JDK 17 required for RN 0.86 / Expo SDK 57 Gradle
export JAVA_HOME=$(/usr/libexec/java_home -v 17)
 
# Loop until device is ready (CI emulator boot)
adb wait-for-device shell 'while [[ -z $(getprop sys.boot_completed) ]]; do sleep 1; done'

Gotchas

Forgot adb reverse on USB - dev client shows "Unable to load script". Fix: adb reverse tcp:8081 tcp:8081 after every reconnect.
Multiple devices, no -s SERIAL - adb: more than one device/emulator. Fix: adb devices then suffix every command.
Installing release AAB with adb install - fails; wrong artifact type. Fix: internal APK profile or Play internal track - Internal Testing Tracks.
Logcat flood without filters - thousands of lines/sec hide RN errors. Fix: '*:S' ReactNativeJS:V pattern above.
npm install native module without rebuild - JS updates but native code stale. Fix: npx expo run:android or install fresh EAS dev APK.
Wireless debugging drops - adb disconnect then re-pair. Fix: USB for reliable reverse during native debugging.

Alternatives

Alternative	Use When	Don't Use When
`npx expo run:android`	Daily Gradle compile + install	APK already built in CI
Android Studio Logcat GUI	Multi-filter UI, pinning threads	Headless CI - use `adb logcat`
`npx expo start --tunnel`	No USB, LAN blocked	USB available - `reverse` is faster
Wireless `adb connect`	Cable-free desk	Need stable Metro during long debug

FAQs

Why does emulator see Metro but USB phone does not?

Emulator uses 10.0.2.2 to reach host localhost - physical devices do not.
Use adb reverse on USB or --host lan with correct laptop IP on Wi-Fi.

How do I find the installable APK path after expo run:android?

android/app/build/outputs/apk/debug/app-debug.apk for standard debug builds.
EAS artifacts download from eas build:list - see jq, rg & JSON Logs.

adb unauthorized after macOS update?

Revoke USB debugging authorizations on the phone (Developer options).
Replug cable and accept the RSA fingerprint dialog.

Can I grant permissions from adb?

adb shell pm grant com.example.app android.permission.CAMERA
Runtime permissions still may need in-app prompts on Android 13+ for notifications.

Does adb work on iOS?

No - use xcrun simctl and Xcode devices window for Apple platforms.

CLI Basics for RN - expo run:android and EAS commands
xcrun simctl & iOS Simulators - iOS counterpart
jq, rg & JSON Logs - parse eas build:list --json for APK URLs
Android Basics for RN Devs - Gradle, ANDROID_HOME, JDK 17
EAS Build Basics - development vs preview APK profiles
Internal Testing Tracks - Play distribution when adb install is not the path

Stack versions: This page was written for React 19.2.3, React Native 0.86.0, and Expo SDK 57 (expo ~57.0.4).

Recipe

Quick-reference recipe card - copy-paste ready.

# Verify toolchain + device
export ANDROID_HOME="$HOME/Library/Android/sdk"
export PATH="$PATH:$ANDROID_HOME/platform-tools"
adb devices -l
 
# USB dev: Metro port reverse (8081 default)
adb reverse tcp:8081 tcp:8081
npx expo start --dev-client
 
# RN-focused logcat
adb logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E
 
# Install dev APK (EAS internal or local debug)
adb install -r ./build/app-debug.apk
adb shell am start -n com.example.app/.MainActivity

When to reach for this:

npx expo run:android cannot see a device (no devices/emulators found).
USB hardware cannot load the JS bundle - Metro works on emulator but not phone.
You need native crash stack traces beyond the redbox.
CI or QA installs a prebuilt APK without Gradle on the laptop.
Deep link or notification cold-start must be scripted for Maestro prep.

Working Example

USB physical device: reverse Metro, install dev client, tail logs, open deep link.

#!/usr/bin/env bash
set -euo pipefail
 
PACKAGE="com.example.shopapp"
APK="./shopapp-debug.apk"   # from eas build --profile development --platform android
 
# 1. Single device guard
SERIAL=$(adb devices | awk 'NR>1 && $2=="device" {print $1; exit}')
if [[ -z "$SERIAL" ]]; then
  echo "No adb device in 'device' state. Enable USB debugging." >&2
  exit 1
fi
echo "Using device: $SERIAL"
 
# 2. Port reverse for Metro (USB)
adb -s "$SERIAL" reverse tcp:8081 tcp:8081
adb -s "$SERIAL" reverse --list
 
# 3. Install / upgrade dev client
adb -s "$SERIAL" install -r "$APK"
 
# 4. Cold start main activity
adb -s "$SERIAL" shell am force-stop "$PACKAGE"
adb -s "$SERIAL" shell am start -n "$PACKAGE/.MainActivity"
 
# 5. Deep link smoke
adb -s "$SERIAL" shell am start -a android.intent.action.VIEW \
  -d "shopapp://orders/42" "$PACKAGE"
 
# 6. Logs in second terminal - native crashes + JS console
adb -s "$SERIAL" logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E

Start Metro (separate terminal):

npx expo start --dev-client --clear

What this demonstrates:

-s SERIAL - mandatory when emulator and phone are both connected.
adb reverse - USB path to Metro without Wi-Fi IP alignment.
install -r - replaces existing debug build while keeping app data (usually).
am start -a VIEW -d - intent filter / deep link verification from bash.
Filtered logcat - surfaces ReactNativeJS and fatal AndroidRuntime errors.

Deep Dive

How It Works

adb speaks to adbd on the device/emulator over USB or TCP (wireless debugging).
Metro serves JS on localhost:8081 on your laptop - the device needs a path to that port (reverse, shared LAN IP, or tunnel).
npx expo run:android invokes Gradle installDebug then launches the app - adb install skips compile when you already have an APK.
Dev clients built with expo-dev-client still need Metro for JS - adb reverse is the USB shortcut.

Device Discovery

adb devices -l                    # serial, state, model
adb kill-server && adb start-server # reset daemon when devices flap
adb -e <cmd>                        # only emulator
adb -d <cmd>                        # only USB device

State	Meaning	Fix
`device`	Ready	Proceed
`unauthorized`	RSA key not accepted on phone	Tap "Allow USB debugging"
`offline`	Cable/driver glitch	Replug, `adb kill-server`
empty list	No emulator running	Android Studio AVD or `emulator -avd <name>`

# List AVDs and boot one (emulator binary is in ANDROID_HOME)
emulator -list-avds
emulator -avd Pixel_8_API_35 &
adb wait-for-device

Port Reverse & Forward

# Metro (default 8081)
adb reverse tcp:8081 tcp:8081
 
# DevTools or custom packager port
adb reverse tcp:8082 tcp:8082
 
# Show active reverses
adb reverse --list
 
# Remove all reverses
adb reverse --remove-all
 
# Forward device port to laptop (less common in RN)
adb forward tcp:9000 tcp:9000

Wi-Fi dev - skip reverse; use npx expo start --dev-client --host lan and ensure phone and laptop share subnet.
Corporate VPN - often breaks LAN; try --tunnel on Metro or USB reverse.

logcat Recipes

# RN daily driver
adb logcat '*:S' ReactNative:V ReactNativeJS:V AndroidRuntime:E
 
# Clear buffer before reproducing a crash
adb logcat -c && adb logcat '*:S' ReactNativeJS:V AndroidRuntime:E
 
# Save to file for CI artifact
adb logcat -d > android-logcat.txt
 
# Filter by PID after launch (adb shell pidof)
PID=$(adb shell pidof -s com.example.app)
adb logcat --pid="$PID"
 
# Kotlin/Java crash stack only
adb logcat '*:S' AndroidRuntime:E

Install & Launch

# Debug APK from expo run:android
adb install -r android/app/build/outputs/apk/debug/app-debug.apk
 
# EAS internal distribution APK
adb install -r ./downloads/shopapp.apk
 
# Uninstall clean
adb uninstall com.example.app
 
# Launch launcher activity
adb shell monkey -p com.example.app -c android.intent.category.LAUNCHER 1
 
# Force stop
adb shell am force-stop com.example.app
 
# Clear app data (logout / corrupted storage)
adb shell pm clear com.example.app

applicationId in app.config.ts (android.package) must match adb package strings.
Play-signed AAB from production eas build is not installable via adb - use internal APK/AAB track or bundletool.

Shell Utilities

# Screenshot (PNG to stdout redirected)
adb exec-out screencap -p > screen.png
 
# Screen record (max 180s on many devices)
adb shell screenrecord /sdcard/demo.mp4
adb pull /sdcard/demo.mp4
 
# Input text (ASCII only - no spaces without %s)
adb shell input text "hello"
 
# Open system settings deep link
adb shell am start -a android.settings.APPLICATION_DETAILS_SETTINGS \
  -d package:com.example.app

Bash Notes

# macOS default SDK path - align with Android Studio install
export ANDROID_HOME="$HOME/Library/Android/sdk"
export PATH="$PATH:$ANDROID_HOME/platform-tools:$ANDROID_HOME/emulator"
 
# JDK 17 required for RN 0.86 / Expo SDK 57 Gradle
export JAVA_HOME=$(/usr/libexec/java_home -v 17)
 
# Loop until device is ready (CI emulator boot)
adb wait-for-device shell 'while [[ -z $(getprop sys.boot_completed) ]]; do sleep 1; done'

Gotchas

Forgot adb reverse on USB - dev client shows "Unable to load script". Fix: adb reverse tcp:8081 tcp:8081 after every reconnect.
Multiple devices, no -s SERIAL - adb: more than one device/emulator. Fix: adb devices then suffix every command.
Installing release AAB with adb install - fails; wrong artifact type. Fix: internal APK profile or Play internal track - Internal Testing Tracks.
Logcat flood without filters - thousands of lines/sec hide RN errors. Fix: '*:S' ReactNativeJS:V pattern above.
npm install native module without rebuild - JS updates but native code stale. Fix: npx expo run:android or install fresh EAS dev APK.
Wireless debugging drops - adb disconnect then re-pair. Fix: USB for reliable reverse during native debugging.

Alternatives

Alternative	Use When	Don't Use When
`npx expo run:android`	Daily Gradle compile + install	APK already built in CI
Android Studio Logcat GUI	Multi-filter UI, pinning threads	Headless CI - use `adb logcat`
`npx expo start --tunnel`	No USB, LAN blocked	USB available - `reverse` is faster
Wireless `adb connect`	Cable-free desk	Need stable Metro during long debug

FAQs

Why does emulator see Metro but USB phone does not?

Emulator uses 10.0.2.2 to reach host localhost - physical devices do not.
Use adb reverse on USB or --host lan with correct laptop IP on Wi-Fi.

How do I find the installable APK path after expo run:android?

android/app/build/outputs/apk/debug/app-debug.apk for standard debug builds.
EAS artifacts download from eas build:list - see jq, rg & JSON Logs.

adb unauthorized after macOS update?

Revoke USB debugging authorizations on the phone (Developer options).
Replug cable and accept the RSA fingerprint dialog.

Can I grant permissions from adb?

adb shell pm grant com.example.app android.permission.CAMERA
Runtime permissions still may need in-app prompts on Android 13+ for notifications.

Does adb work on iOS?

No - use xcrun simctl and Xcode devices window for Apple platforms.

CLI Basics for RN - expo run:android and EAS commands
xcrun simctl & iOS Simulators - iOS counterpart
jq, rg & JSON Logs - parse eas build:list --json for APK URLs
Android Basics for RN Devs - Gradle, ANDROID_HOME, JDK 17
EAS Build Basics - development vs preview APK profiles
Internal Testing Tracks - Play distribution when adb install is not the path

Stack versions: This page was written for React 19.2.3, React Native 0.86.0, and Expo SDK 57 (expo ~57.0.4).

adb & Android Devices

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adb & Android Devices