adb-logcat
View Android system and app logs
TLDR
Display system logs
Display lines that match a reg[e]x
Display logs for a tag in a specific mode ([V]erbose, [D]ebug, [I]nfo, [W]arning, [E]rror, [F]atal, [S]ilent), filtering other tags
Display logs for React Native applications in [V]erbose mode [S]ilencing other tags
Display logs for all tags with priority level [W]arning and higher
Display logs for a specific PID
Display logs for the process of a specific package
Color the log (usually use with filters)
SYNOPSIS
adb logcat [options] [filter-specs]
PARAMETERS
-a
Print all buffers (default: all)
-b <buffer>
Request alternate buffer: main, system, radio, events, crash, or default
-B <buffer>
Request alternate buffer with bigger size
-c
Clear (flush) entire log and exit
-C
Color output
-d
Dump log and exit (non-blocking)
-D
Dump log decoded and exit
-e <expr>
Print lines matching regex <expr>
-f <filename>
Log to file <filename> (default: stdout)
-g
Get size of log ring buffer and exit
-h
Display help
-i
Print row IDs for messages
-l <prio>
Print only <prio> level or higher (numeric)
-m <count>
Set rotation size of log
-n <count>
Number of rotations for log size
-P <file>
Save process/thread IDs to <file>
-q
Don't suppress ASCII control chars
-r <kbytes>
Rotate log every <kbytes> (16 default)
-s <tag>[:<prio>]
Print logs for <tag> at <prio>
-S <file>
Save logs in binary to <file>
-t <count>
Print most recent <count> lines (with -d)
-T <count>
Print most recent <count> lines (no -d)
-u <prio>
Update log to given priority (numeric)
-v <format>
Log format: brief, process, tag, thread, threadtime, long, raw, etc.
-w
Recover from bad headers
DESCRIPTION
adb logcat is a powerful command-line tool in the Android Debug Bridge (ADB) suite for viewing, filtering, and dumping log messages from Android devices or emulators. It captures real-time logs from multiple sources including kernel ring buffers, applications, system services, radio, and crash reports. Logs are prioritized and color-coded: Verbose (V, gray), Debug (D, green), Info (I, blue), Warn (W, yellow), Error (E, red), Fatal (F, purple), and Silent (S, suppressed).
Primarily used for debugging apps and system issues, it streams continuously by default (Ctrl+C to stop). Developers filter by tags, priorities, PIDs, or regex to isolate relevant output. Output formats range from brief to detailed timestamps. It supports writing to files, rotation for large logs, and clearing buffers. Essential for Android development, it helps trace crashes, ANRs, and performance problems without rooting the device.
CAVEATS
Requires ADB installed, device connected via USB/Wi-Fi, and USB debugging enabled.
Verbose output can overwhelm terminals or impact device performance.
Multiple devices need -s serial selector.
LOG PRIORITIES
V/Verbose, D/Debug, I/Info, W/Warn, E/Error, F/Fatal, S/Silent.
Use like *:E to filter errors.
FILTER SPECS
Syntax: <tag>:<priority>
Examples: ActivityManager:I, package:com.example*:S, *:E (all errors).
COMMON BUFFERS
main: app logs; system: HAL/services; radio: telephony; events: kernel events; crash: crashes.
HISTORY
Part of Android SDK platform-tools since Android 1.0 (2008). Evolved with multi-buffer support in Android 4.0+, format options, rotation in later versions for better debugging.
SEE ALSO
adb(1), dmesg(1), journalctl(1)
