iOS and Android Device Logs

Complete guide to viewing and filtering device logs on iOS and Android.

When to Use This Skill User needs to see device logs User is debugging crashes User wants to filter logs by app User needs real-time log streaming User asks "how to see logs" Quick Commands

iOS - Stream logs from connected device

xcrun devicectl device log stream --device

iOS - Stream from simulator

xcrun simctl spawn booted log stream

Android - Stream all logs

adb logcat

Android - Filter by package

adb logcat --pid=$(adb shell pidof com.yourapp.id)

iOS Logs Method 1: Console.app (GUI) Open Console.app (Applications > Utilities) Select your device in sidebar Click "Start Streaming" Use search to filter: By process: process:YourApp By subsystem: subsystem:com.yourapp By message: "error" Method 2: devicectl (CLI - Recommended)

List connected devices

xcrun devicectl list devices

Stream logs from specific device

xcrun devicectl device log stream --device

Stream with predicate filter

xcrun devicectl device log stream --device \ --predicate 'process == "YourApp"'

Stream specific log levels

xcrun devicectl device log stream --device \ --level error

Save to file

xcrun devicectl device log stream --device \ --predicate 'process == "YourApp"' > app_logs.txt

Method 3: simctl for Simulators

Stream logs from booted simulator

xcrun simctl spawn booted log stream

Filter by process

xcrun simctl spawn booted log stream --predicate 'process == "YourApp"'

Filter by subsystem

xcrun simctl spawn booted log stream --predicate 'subsystem == "com.yourapp"'

Show only errors

xcrun simctl spawn booted log stream --level error

Combine filters

xcrun simctl spawn booted log stream \ --predicate 'process == "YourApp" AND messageType == error'

Method 4: Xcode Device Logs Window > Devices and Simulators Select device Click "Open Console" Or: View device logs for crash reports iOS Log Predicate Examples

Process name

--predicate 'process == "YourApp"'

Contains text

--predicate 'eventMessage contains "error"'

Subsystem

--predicate 'subsystem == "com.yourapp.plugin"'

Category

--predicate 'category == "network"'

Log level

--predicate 'messageType == error'

Combined

--predicate 'process == "YourApp" AND messageType >= error'

Time-based (last 5 minutes)

--predicate 'timestamp > now - 5m'

iOS Log Levels Level Description default Default messages info Informational debug Debug (hidden by default) error Error conditions fault Fault/critical Android Logs Method 1: adb logcat (CLI)

Basic log stream

adb logcat

Clear logs first, then stream

adb logcat -c && adb logcat

Filter by tag

adb logcat -s MyTag:D

Filter by priority

adb logcat *:E # Only errors and above

Filter by package name

adb logcat --pid=$(adb shell pidof com.yourapp.id)

Filter by multiple tags

adb logcat -s "MyPlugin:D" "Capacitor:I"

Save to file

adb logcat > logs.txt

Save to file with timestamp

adb logcat -v time > logs.txt

Method 2: Android Studio Logcat (GUI) View > Tool Windows > Logcat Use filter dropdown: Package: package:com.yourapp Tag: tag:MyPlugin Level: level:error Create saved filters for quick access Method 3: pidcat (Better CLI Tool)

Install pidcat

pip install pidcat

Stream logs for package

pidcat com.yourapp.id

With tag filter

pidcat -t MyPlugin com.yourapp.id

Android Log Priority Levels Letter Priority V Verbose D Debug I Info W Warn E Error F Fatal S Silent adb logcat Format Options

Different output formats

adb logcat -v brief # Default adb logcat -v process # PID only adb logcat -v tag # Tag only adb logcat -v time # With timestamp adb logcat -v threadtime # With thread and time adb logcat -v long # All metadata

Colorized output

adb logcat -v color

Show recent logs (last N lines)

adb logcat -d -t 100

Show logs since timestamp

adb logcat -v time -T "01-25 10:00:00.000"

Common Android Filters

Capacitor core logs

adb logcat -s "Capacitor:*"

Plugin-specific logs

adb logcat -s "CapacitorNativeBiometric:*"

WebView logs (JavaScript console)

adb logcat -s "chromium:*"

JavaScript errors

adb logcat | grep -i "js error|uncaught"

Crash logs

adb logcat | grep -iE "fatal|crash|exception"

Network logs

adb logcat -s "OkHttp:" "NetworkSecurityConfig:"

Viewing Crash Logs iOS Crash Logs

Copy crash logs from device

xcrun devicectl device copy crashlog --device ./crashes/

View in Console.app

User Diagnostics Reports section

Or find at:

Device: Settings > Privacy > Analytics & Improvements > Analytics Data

Mac: ~/Library/Logs/DiagnosticReports/

Android Crash Logs

Get tombstone (native crash)

adb shell cat /data/tombstones/tombstone_00

Get ANR traces

adb pull /data/anr/traces.txt

Get bugreport (comprehensive)

adb bugreport > bugreport.zip

MCP Integration

Use MCP tools to fetch logs programmatically:

// Example MCP tool for fetching iOS logs const logs = await mcp.ios.streamLogs({ device: 'booted', predicate: 'process == "YourApp"', level: 'debug', });

// Example MCP tool for Android logs const androidLogs = await mcp.android.logcat({ package: 'com.yourapp.id', level: 'D', });

Log Parsing Tips Extract JavaScript Errors

iOS - JavaScript console logs

xcrun simctl spawn booted log stream \ --predicate 'eventMessage contains "JS:"'

Android - WebView console

adb logcat chromium:I *:S | grep "console"

Filter Network Requests

iOS

xcrun simctl spawn booted log stream \ --predicate 'subsystem == "com.apple.network"'

Android

adb logcat -s "NetworkSecurityConfig:" "OkHttp:"

Monitor Memory

iOS - Memory pressure

xcrun simctl spawn booted log stream \ --predicate 'eventMessage contains "memory"'

Android - Memory info

adb shell dumpsys meminfo com.yourapp.id

Troubleshooting Issue: No Logs Showing

iOS:

Ensure device is trusted: Xcode > Window > Devices Try restarting log stream Check Console.app filters

Android:

Enable USB debugging Run adb devices to verify connection Try adb kill-server && adb start-server Issue: Too Many Logs

Use filters:

iOS - Only your app

--predicate 'process == "YourApp" AND messageType >= info'

Android - Only your package

adb logcat --pid=$(adb shell pidof com.yourapp.id)

Issue: Missing Debug Logs

iOS: Debug logs are hidden by default

Enable debug logs

xcrun simctl spawn booted log stream --level debug

Android: Ensure log level is set correctly

Log.d("Tag", "Debug message") // D level

Best Practices Use structured logging - Include context in log messages Add timestamps - Helps correlate events Filter early - Don't stream all logs Save important logs - Redirect to file for later analysis Use log levels appropriately - Debug for dev, error for production Resources iOS Unified Logging: https://developer.apple.com/documentation/os/logging Android Logcat: https://developer.android.com/studio/debug/logcat devicectl Reference: https://developer.apple.com/documentation/devicemanagement