Tommy Lahitte
Debugging

Control Log Verbosity Per Category at Launch

Drowning in log noise or missing critical messages? The -LogCmds launch argument lets you set verbosity per log category without recompiling, from silencing entire subsystems to enabling Verbose output for one specific category.

loggingverbositylaunch-argsdebugginglogcmds

Unreal's log system has hundreds of categories, each with its own verbosity level. The -LogCmds argument overrides them at launch, which is much faster than editing DefaultEngine.ini or recompiling.

Syntax

bash
-LogCmds="LogCategoryName Verbosity, AnotherCategory Verbosity"

Practical Examples

bash
# Enable verbose for Level Snapshots
-LogCmds="LogLevelSnapshots Verbose"

# Enable verbose for media playback debugging
-LogCmds="LogImgMedia Verbose, LogElectraPlayer Verbose, LogElectraPlayerPlugin Verbose"

# Silence a noisy category
-LogCmds="LogNetDormancy NoLogging"

# Multiple categories in one argument
-LogCmds="LogLevelSnapshots Verbose, LogImgMedia Verbose, LogNetDormancy NoLogging"

Verbosity Levels (lowest to highest)

  • NoLogging: suppress all output from this category
  • Fatal: only fatal errors
  • Error: errors and fatals
  • Warning: warnings, errors, and fatals
  • Display: important info (default for most categories)
  • Log: general log messages
  • Verbose: detailed trace output
  • VeryVerbose: maximum detail (very noisy)

Setting Verbosity at Runtime

You can also change verbosity live from the Unreal console without restarting:

bash
Log LogLevelSnapshots Verbose
Log LogImgMedia VeryVerbose
To find the correct category name, search the source code for DEFINE_LOG_CATEGORY or look at existing log output. The category name appears in brackets before each message.

Related Tips

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When Unreal crashes on the GPU side with no useful callstack, two launch arguments (-d3ddebug and -gpucrashdebugging) enable the D3D validation layer and NVIDIA Aftermath/Breadcrumbs to capture the exact operation that caused the crash.

Mastering Output Log Filters in Unreal Editor

The Output Log is noisy by default. Learn to use categories, verbosity levels, and custom log channels to cut through the noise and surface exactly the signal you need.

Track Down Memory Corruption with Stomp2Malloc

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