Command Line Arguments

Note: This page is still a work in progress.

This is an early preview of a page documenting all command line arguments.

The aim is to:

  • create an exhaustive list of all command line arguments
  • clarify whether they are used for the editor exe or built game exe
  • comment on the usage and purpose of arguments

Debug

-

WaitForDebugger

Type:

flag

Causes Unreal to wait for a debugger to be connected before continuing execution.

Logging

-

Log

="abc"
Type:

string

Related:

When used as a switch (-log), opens a separate window to display the contents of the log in real time. When used as a setting (LOG=filename.log), tells the engine to use the log filename of the string that immediately follows.

Unreal Documentation
-

LogTimes

Type:

flag

Opposite:

There are a bunch of different ways to display log times.

Print time with log output. (Default, same as setting LogTimes=True in the [LogFiles] section of *Engine.ini.)

Unreal Documentation
-

UTCLogTimes

Type:

flag

Opposite:
-

LocalLogTimes

Type:

flag

Opposite:
-

LogTimesSinceStart

Type:

flag

Opposite:
-

LogTimeCode

Type:

flag

Opposite:
-

NoLogTimes

Do not print time with log output. (Same as setting LogTimes=False in the [LogFiles] section of *Engine.ini.)

Unreal Documentation
-

AbsLog

="abc"
Type:

string

Related:

Same as LOG= but without a filename length check.

Unreal Documentation
-

LogCmds

="abc"
Type:

string

Change the verbosity of log categories

-

ForceLogFlush

Type:

flag

Force a log flush after each line.

Unreal Documentation
-

NoPause

Type:

flag

Related:

Close the log window automatically on exit.

Unreal Documentation
-

NoPauseOnSuccess

Type:

flag

Related:

Close the log window automatically on exit as long as no errors were present.

Unreal Documentation
-

NoWrite

Type:

flag

Disable output to log.

Unreal Documentation

Stats

-

LightMassStats

Type:

flag

Force all lightmass agents to report detailed stats to the log.

Unreal Documentation

Developer

-

Auto

Type:

flag

Assume yes on all questions. (for example during compile)

Unreal Documentation
-

AutoCheckoutPackages

Type:

flag

Used on ResavePackagesCommandlet.

Automatically checkout packages that need to be saved.

Unreal Documentation
-

AutomatedMapBuild

Type:

flag

The second argument to the exe is the map, so this flag uses that. As to what an "automated build" means, I have no idea.

Perform an automated build of a specified map.

Unreal Documentation
-

BuildMachine

Type:

flag

If this is set, it implies some other arguments?

Set as build machine. Used for deciding if debug output is enabled.

Unreal Documentation
-

CrashReports

Type:

flag

Always report crashes of the engine.

Unreal Documentation
-

D3DDebug

Type:

flag

Use a d3d debug device.

Unreal Documentation
-

Deterministic

Type:

flag

Shortcut for -UseFixedTimeStep -FixedSeed.

-

FixedSeed

Type:

flag

Initialize the random number generator with a fixed value, 0.

Unreal Documentation
-

UseFixedTimeStep

Type:

flag

-

FixUpTangents

Type:

flag

Fix legacy tangents in distributions automatically.

Unreal Documentation
-

ForcePVRTC

Type:

flag

Found a reference to "bForcePVRTC".

Force pvrtc texture compression for mobile platform.

Unreal Documentation
-

Installed

Type:

flag

Opposite:

For development purposes, run the game as if installed.

Unreal Documentation
-

NotInstalled

Type:

flag

Opposite:
-

InstallFW

Type:

flag

Opposite:

Shows the Windows firewall popup maybe?

Set whether the handling of the firewall integration should be performed.

Unreal Documentation
-

UninstallFW

Type:

flag

Opposite:

Set whether the handling of the firewall integration should be performed.

Unreal Documentation
-

InstallGE

Type:

flag

Opposite:
Related:

Game Explorer seems to be some old Windows thing for managing installed games. Not sure if it's really relevant any more.

Add the game to the Game Explorer.

Unreal Documentation
-

UninstallGE

Type:

flag

Opposite:

Remove the game from the Game Explorer.

Unreal Documentation
-

AllUsers

Type:

flag

does this mean this requires InstallGe?

Add the game for all users when INSTALLGE is specified.

Unreal Documentation
-

LightMassDebug

Type:

flag

Launch lightmass manually with -debug and allow lightmass to be executed multiple times.

Unreal Documentation
-

NoContentBrowser

Type:

flag

Surely this is editor-only? Why would you want to disable the content browser?

Disable the Content Browser.

Unreal Documentation
-

NoInnerException

Type:

flag

Seems to only be enabled with the define _WIN64?Why might you do this? S

Disable the exception handler within native C++.

Unreal Documentation
#ifdef _WIN64
if ( FParse::Param(CmdLine,TEXT("noinnerexception")) || FApp::IsBenchmarking() || bNoExceptionHandler)
{
  GEnableInnerException = false;
}
#endif
-

NoLoadStartupPackages

Type:

flag

There is a log message that mentions it but I cannot find any code that actually uses it.

Force startup packages not to be loaded. You can use this if objects in a startup package must be deleted from within the editor.

Unreal Documentation
-

NoRC

Type:

flag

Disable the remote control. Used for dedicated servers.

Unreal Documentation
-

VerifyGC

Type:

flag

Opposite:

Force garbage compiler assumptions to be verified.

Unreal Documentation
-

NoVerifyGC

Type:

flag

Opposite:

Do not verify garbage compiler assumptions.

Unreal Documentation
-

SeekFreeLoading

Type:

flag

Only use cooked data.

Unreal Documentation
-

SeekFreePackageMap

Type:

flag

Override the package map with the seekfree (cooked) version.

Unreal Documentation
-

SeekFreeloadingPCConsole

Type:

flag

Only use cooked data for PC console mode.

Unreal Documentation
-

SeekFreeLoadingServer

Type:

flag

Only use cooked data for server.

Unreal Documentation
-

SetThreadNames

Type:

flag

(Xbox only) Force thread names to be set. This can mess up the XDK COM API which is why it must be explicitly set to be performed if desired.

Unreal Documentation
-

ShowMissingLoc

Type:

flag

Can't find this in the source. Also, I thought that error strings are already returned instead of English. Maybe this is editor-only?

If missing localized text, return error string instead of English text.

Unreal Documentation
-

Silent

Type:

flag

Disable output and feedback.

Unreal Documentation
-

TreatLoadWarningsAsErrors

Type:

flag

What happens if there's an error?

Force load warnings to be treated as errors.

Unreal Documentation
-

WarningsAsErrors

Type:

flag

Treat warnings as errors.

Unreal Documentation
-

Unattended

Type:

flag

What kinds of things require feedback? When might you want to use this?

Set as unattended. Disable anything requiring feedback from user.

Unreal Documentation
-

UseUnpublished

Type:

flag

Force packages in the Unpublished folder to be used.

Unreal Documentation
-

VADebug

Type:

flag

Use the Visual Studio debugger interface.

Unreal Documentation
-

Verbose

Type:

flag

Set compiler to use verbose output.

Unreal Documentation
-

ExecCmds

="abc"
Type:

string

It looks like this can be used to execute cheat console commands, separated with commas.

Deprecated

-

BiasCompressionForSize

Type:

flag

Can't find this in the engine.

Override compression settings with respect to size.

Unreal Documentation
-

BulkImportingSounds

Type:

flag

Can't find this in the engine.

Use when importing sounds in bulk. (Content Browser specific.)

Unreal Documentation
-

Check_Native_Class_Sizes

Type:

flag

Can't find in source.

Enable checking of native class sizes. Note: Native classes on console platforms will cause native class size checks to fail even though they are assumed to be correct.

Unreal Documentation
-

CoderMode

Type:

flag

Couldn't find it in the codebase for UE5. Possibly for Unreal Engine 3?

Enables Coder mode.

Unreal Documentation
-

CompatScale

Type:

flag

Couldn't find in source.

Set compatibility settings manually to override PCCompat tool settings.

Unreal Documentation
-

ConformDir

Type:

flag

Can't find either ConformDir or ConfirmDir in UE5 source.

Directory to use when conforming packages.

Unreal Documentation
-

CookForDemo

Type:

flag

Cannot find in source.

Specify as cooking packages for the demo.

Unreal Documentation
-

CookPackages

Type:

flag

Cannot find in source.

Tag to specify cooking packages.

Unreal Documentation
-

DevCon

Type:

flag

Cannot find in source

Disable secure connections for developers. (Uses unencrypted sockets.)

Unreal Documentation
-

DumpFileIOStats

Type:

flag

Cannot find in source

Track and log File IO statistics.

Unreal Documentation
-

ForceSoundRecook

Type:

flag

Can't find any reference to this. Deprecated?

Force a complete re-cook of all sounds.

Unreal Documentation
-

GenericBrowser

Type:

flag

Can't find any reference to this. Deprecated?

Use the Generic Browser.

Unreal Documentation
-

NoConform

Type:

flag

Cannot find in source.

Tell the engine not to conform packages as they are compiled.

Unreal Documentation
-

TraceAnimUsage

Type:

flag

Cannot find in source.

Trace animation usage.

Unreal Documentation
-

Seconds

Type:

I couldn't find this in the Unreal Engine 5 codebase.

Set the maximum tick time.

Unreal Documentation
-

PrimaryNet

Type:

flag

Couldn't find this in the source code, deprecated?

Affect how the engine handles network binding.

Unreal Documentation
-

PreferredProcessor

Type:

flag

Can't find in source.

Set the thread affinity for a specific processor.

Unreal Documentation
-

EnglishCoalesced

Type:

flag

Couldn't find in source.

Revert to the default (English) coalesced .ini if the language-localized version cannot be found.

Unreal Documentation

Localization

-

Culture

="abc"
Type:

string

Related:

When this is set, the text localization manager uses the specified culture and does not look at ini files.

It seems like it might be useful for testing localization, to force the game to launch with a specific culture without having to mess around with settings.

-

CultureForCooking

="abc"
Type:

string

Related:

Does the same as Culture but can has the option to work with FirstInstall.

Set language to be used for cooking.

Unreal Documentation
-

FirstInstall

Type:

Based on the code, if CultureForCooking and FirstInstall are set, it writes the culture specified by CultureForCooking to the Internationalization part of the engine .ini file.

Rendering

-

ConsoleX

=123
Type:

integer

Set the horizontal position for console output window.

Unreal Documentation
-

ConsoleY

=123
Type:

integer

Set the vertical position for console output window.

Unreal Documentation
-

ConsoleWidth

=123
Type:

integer

-

ConsoleHeight

=123
Type:

integer

-

WinX

=123
Type:

integer

Set the horizontal position of the game window on the screen.

Unreal Documentation
-

WinY

=123
Type:

integer

Set the vertical position of the game window on the screen.

Unreal Documentation
-

ResX

=123
Type:

integer

Set horizontal resolution for game window.

Unreal Documentation
-

ResY

=123
Type:

integer

Set vertical resolution for game window.

Unreal Documentation
-

VSync

Type:

flag

Opposite:

Activate the VSYNC via command line. Pprevents tearing of the image but costs fps and causes input latency.)

Unreal Documentation
-

NoVSync

Type:

flag

Opposite:

Deactivate the VSYNC via command line.

Unreal Documentation
-

Benchmark

Type:

flag

Run game at fixed-step in order to process each frame without skipping any frames. This is useful in conjunction with DUMPMOVIE options.

Unreal Documentation
-

DumpMovie

Type:

flag

Sets the GIsDumpingMovie variable to -1 so it dumps for an unspecified time. Can also be set through the console variable r.DumpingMovie Is a flag, cannot set it to dump for a defined amoutn of time like the console variable or global variable.

Dump rendered frames to files using current resolution of game.

Unreal Documentation
- IConsoleManager::Get().RegisterConsoleVariableRef(TEXT("r.DumpingMovie"),
    GIsDumpingMovie,
    TEXT("Allows to dump each rendered frame to disk (slow fps, names MovieFrame..).\n")
    TEXT("<=0:off (default), <0:remains on, >0:remains on for n frames (n is the number specified)"),
    ECVF_Cheat);
-

Exec

Type:

flag

What is an exec file? Is it really related to rendering?

Executes the specified exec file.

Unreal Documentation
-

FPS

=123
Type:

integer

Set the frames per second for benchmarking.

Unreal Documentation
-

Fullscreen

Type:

flag

Opposite:

Set game to run in fullscreen mode.

Unreal Documentation
-

Windowed

Type:

flag

Opposite:

Set game to run in windowed mode.

Unreal Documentation

Network

-

LanPlay

Type:

flag

Tell the engine to not cap client bandwidth when connecting to servers. Causes double the amount of server updates and can saturate client's bandwidth.

Unreal Documentation
-

LimitClientTicks

Type:

flag

See NetDriver.cpp. This flag seems to be on by default if GetNetMode() == NM_ListenServer

Force throttling of network updates.

Unreal Documentation
#if WITH_SERVER_CODE
int32 UNetDriver::ServerReplicateActors_PrepConnections( const float DeltaSeconds )
{
  int32 NumClientsToTick = ClientConnections.Num();

  // by default only throttle update for listen servers unless specified on the commandline
  static bool bForceClientTickingThrottle = FParse::Param( FCommandLine::Get(), TEXT( "limitclientticks" ) );
  if ( bForceClientTickingThrottle || GetNetMode() == NM_ListenServer )
  {
      // ...
-

MultiHome

Type:

flag

Tell the engine to use a multihome address for networking.

Unreal Documentation
-

MultiHomeHttp

Type:

flag

Tell the engine to use a multihome address for networking.

Unreal Documentation
-

NetworkProfiler

Type:

flag

Enable network profiler tracking.

Unreal Documentation
-

NoSteam

Type:

flag

Set steamworks to not be used.

Unreal Documentation
-

Port

="abc"
Type:

string

Tell the engine to use a specific port number.

Unreal Documentation

User

-

NoHomeDir

Type:

flag

So what does it do instead?

Override use of My Documents folder as home directory.

Unreal Documentation
-

NoForceFeedback

Type:

flag

Disable force feedback in the engine.

Unreal Documentation
-

NoSound

Type:

flag

Disable any sound output from the engine.

Unreal Documentation
-

NoSplash

Type:

flag

Disable use of splash image when loading the game.

Unreal Documentation
-

NoTextureStreaming

Type:

flag

Disable texture streaming. Highest quality textures are always loaded.

Unreal Documentation
-

OneThread

Type:

flag

Run the engine using a single thread instead of multi-threading.

Unreal Documentation
-

Paths

="abc"
Type:

string

Set what paths to use for testing wrangled content. Not used for shipping releases.

Unreal Documentation
-

UseAllAvailableCores

Type:

flag

Can only find it with reference to archiving.

Force the use of all available cores on the target platform.

Unreal Documentation

Server Switches

-

Login

="abc"
Type:

string

Set username to use when logging in.

Unreal Documentation
-

Password

="abc"
Type:

string

Set password to use when logging in.

Unreal Documentation

Game Stats/Database

-

NoDatabase

Type:

flag

Do not use database, and ignore database connection errors.

Unreal Documentation
-

NoLiveTags

Type:

flag

Skip loading unverified tag changes from SQL database. Only load for current user.

Unreal Documentation

INI/Config Files

-

NoAutoINIUpdate

Type:

flag

Incompatible with:

Suppress prompts to update .ini files.

Unreal Documentation
-

NoINI

Type:

flag

Do not update the .ini files.

Unreal Documentation
-

RegenerateINIs

Type:

flag

Incompatible with:

Be careful with plurals

Forces .ini files to be regenerated.

Unreal Documentation

Graphics

-

PreferAMD

Type:

flag

Windows DX11

-

PreferIntel

Type:

flag

Part of the Windows D3D12, D3D11 and Vulkan Render Hardware Interfaces, this lets you set a preferred adapter vendor. I guess you might want to use it if you've optimised for one over another, and the user has multiple installed?

-

PreferNVidia

Type:

flag

Part of the Windows D3D12, D3D11 and Vulkan Render Hardware Interfaces, this lets you set a preferred adapter vendor. I guess you might want to use it if you've optimised for one over another, and the user has multiple installed?

-

PreferMS

Type:

flag

Part of the Windows D3D11 Render Hardware Interface only, this lets you set a preferred adapter vendor. I guess you might want to use it if you've optimised for one over another, and the user has multiple installed?

-

AllowSoftwareRendering

Type:

flag

In the D3D11 and D3D12 RHI, setting this allows it to fall back to software rendering. By default it seem this is disabled.

VR

-

NoHMD

Type:

flag

Disables head-mounted display. Useful for disabling SteamVR.

Unknown

-

Multiprocess

Type:

flag

-

MultiprocessSaveConfig

Type:

flag

-

SkipCompile

Type:

flag

-

SystemMalloc

Type:

flag

-

NumThreads

=123
Type:

integer

Minimum 1.

-

NumRuns

=123
Type:

integer

Minimum 1.

-

MemPerThread

=123
Type:

integer

In kilobytes.

-

TouchMem

Type:

flag

Posted: