Unreal Engine 4/5 Scripting System

WARNING: This is the dev version of the UE4SS docs. The API and features are subject to change at any time. If you are developing mods for UE4SS, you should reference the latest release instead.

Lua scripting system platform, C++ Modding API, SDK generator, blueprint mod loader, live property editor and other dumping utilities for UE4/5 games.

Major features

Targeting UE Versions: From 4.12 To 5.5

The goal of UE4SS is not to be a plug-n-play solution that always works with every game. The goal is to have an underlying system that works for most games. You may need to update AOBs on your own, and there's a guide for that below.

Basic Installation

The easiest installation is via downloading the non-dev version of the latest non-experimental build from Releases and extracting the zip content to /{Gameroot}/GameName/Binaries/Win64/.

If your game is in the custom config list, extract the contents from the relevant folder to Win64 as well.

If you are planning on doing mod development using UE4SS, you can do the same as above but download the zDEV version instead.

Full installation guide

Fixing compatibility problems

Lua API - Overview

Generating UHT compatible headers

Custom Game Configs

Creating Compatible Blueprint Mods

UE4SS Discord Server Invite

Unreal Engine Modding Discord Server Invite

Build requirements

  • A computer running Windows.
    • Linux support might happen at some point but not soon.
  • A version of MSVC that supports C++23:
    • MSVC toolset version >= 14.39.0
    • MSVC version >= 19.39.0
    • Visual Studio version >= 17.9
    • More compilers will hopefully be supported in the future.
  • Rust toolchain >= 1.73.0
  • xmake >= 2.9.3

Build instructions

  1. Clone the repo.
  2. Execute this command: git submodule update --init --recursive Make sure your Github account is linked to your Epic Games account for UE source access. Do not use the --remote option because that will force third-party dependencies to update to the latest commit, and that can break things. You will need your github account to be linked to an Epic games account to pull the Unreal pseudo code submodule.

There are several different ways you can build UE4SS.

Building from cli

Configuration settings

xmake allows you to flexibly configure some build options to suit your specific needs. The following is a non-comprehensive list of configuration settings you might find useful.

important

All configuration changes are made by using the xmake config command. You can also use xmake f as an alias for config.

After configuring xmake with any of the following options, you can build the project with xmake or xmake build.

Mode

The build modes are structured as follows: <Target>__<Config>__<Platform>

Currently supported options for these are:

  • Target

    • Game - for regular games on UE versions greater than UE 4.21
    • LessEqual421 - for regular games on UE versions less than or equal to UE 4.21
    • CasePreserving - for games built with case preserving enabled

  • Config

    • Dev - development build
    • Debug - debug build
    • Shipping - shipping(release) build
    • Test - build for tests

  • Platform

    • Win64 - 64-bit windows

tip

Configure the project using this command: xmake f -m "<BuildMode>". -m is an alias for --mode=<BuildMode>.

Patternsleuth (Experimental)

By default, the patternsleuth tool installs itself as an xmake package. If you do not intend on modifying the patternsleuth source code, then you don't have to configure anything special. If you want to be able to modify the patternsleuth source code, you have to supply the --patternsleuth=local option to xmake config in order to recompile patternsleuth as part of the UE4SS build.

Proxy Path

By default, UE4SS generates a proxy based on C:\Windows\System32\dwmapi.dll. If you want to change this for any reason, you can supply the --ue4ssProxyPath=<path proxy dll> to the xmake config command..

Profiler Flavor

By default, UE4SS uses Tracy for profiling. You can pass --profilerFlavor=<profiler> to the xmake config command to set the profiler flavor. The currently supported flavors are Tracy, Superluminal, and None.

Version Check

By default, xmake will check if you have the minimum required version of Rust or MSVC installed (if you are using the MSVC toolchain). If you do not, it will throw an error on the configure step. If you want to ignore this check, you can pass --versionCheck=n to the xmake config command.

Once you set the flag, the option value be set until you specify otherwise.

Therefore, to not check versions when running xmake project -k vsxmake2022, you must first run the xmake config --versionCheck=n command, then run the xmake project -k vsxmake2022 command.

Helpful xmake commands

You may encounter use for the some of the more advanced xmake commands. A non-comprehensive list of some useful commands is included below.

SyntaxAliasesUses
xmake <command> --yesxmake <command> -yAutomatically confirm any user prompts.
xmake --verbose <command>xmake -v <command>Enable verbose level logging.
xmake --Diagnostic <command>xmake -D <command>Enable diagnostic level logging.
xmake --verbose --Diagnostic --yes <command>xmake -vDy <command>You can combine most flags into a single -flagCombo.
xmake configxmake fConfigure xmake with any of these options.
xmake clean --allxmake c --allCleans binaries and intermediate output of all targets.
xmake clean <target>xmake c <target>Cleans binaries and intermediates of a specific target.
xmake buildxmake bIncrementally builds UE4SS using input file detection.
xmake build --rebuildxmake b -rForces a full rebuild of UE4SS.
xmake build <target>xmake b <target>Incrementally builds a specific target.
xmake showShows xmake info and current project info.
xmake show --target=<target>xmake show -t <target>Prints lots of information about a target. Useful for debugging scripts, compiler flags, dependency tree, etc.
xmake require --cleanxmake q -cClears all package caches and uninstalls all not-referenced packages.
xmake require --forcexmake q -fForce re-installs all dependency packages.
xmake require --listxmake q -lLists all packages that are needed for the project.
xmake project --kind=vsxmake2022 --modes="Game__Shipping__Win64"xmake project -k vsxmake2022 -m "Game__Shipping__Win64"Generates a Visual Studio project based on your current xmake configuration. You can specify multiple modes to generate by supplying -m "Comma,Separated,Modes". If you do not supply any modes, the VS project will generate all permutations of modes.

Opening in an IDE

Visual Studio / Rider

To generate Visual Studio project files, run the xmake project -k vsxmake2022 -m "Game__Shipping__Win64" command.

Afterwards open the generated .sln file inside of the vsxmake2022 directory

Note that you should also commit & push the submodules that you've updated if the reason why you updated was not because someone else pushed an update, and you're just catching up to it.

warning

The vs. build plugin performs the compile operation by directly calling the xmake command under vs, and also supports intellisense and definition jumps, as well as breakpoint debugging. This means that modifying the project properties within Visual Studio will not affect which flags are passed to the build when VS executes xmake. XMake provides some configurable project settings which can be found in VS under the Project Properties -> Configuration Properties -> Xmake menu.

caution

If you have multiple Visual Studio versions installed, run xmake f --vs=2022, otherwise you may encounter issues with the project generation.

Configuring additional modes

tip

Additional modes can be generated by running xmake project -k vsxmake2022 -m "Game__Shipping__Win64,Game__Debug__Win64". Further explanation can be found in the xmake command table.

Regenerating solution best practices

caution

If you change your configuration with xmake config, you may need to regenerate your Visual Studio solution to pick up on changes to your configuration. You can simply re-run the xmake project -k vsxmake2022 -m "<modes>" command to regenerate the solution.

Building Windows binaries on Linux

We only officially support msvc-wine for cross-compiling.
Make sure you have winbind (libwbclient & samba on Arch) installed.

caution

You must use xmake v2.9.7 or later, and as of early December 2024, this version is not yet released which means you must install the dev version of xmake.

You need to install the x86_64-pc-windows-msvc target (not the windows-gnu target) with rustup.
When invoking xmake f, you must set --plat, --arch, and --sdk.
You must also use --ue4ssCross=msvc-wine, and disable the version check.
The following projects are not supported when cross-compiling and are automatically disabled:

proxy
proxy_generator
UVTD

When invoking the xmake build command, patternsleuth will automatically be built without xmake.
The binary files are available in deps/first/patternsleuth_bind/target/x86_64-pc-windows-msvc.
They are automatically used by xmake when --ue4ssCross is set to msvc-wine.
Here's an example of a full command that will build Windows binaries on a Linux machine:

xmake f -m "Game__Shipping__Win64" -p windows -a x64 --sdk=/home/<username>/my_msvc/opt/msvc --versionCheck=n --ue4ssCross=msvc-wine

Updating git submodules

If you want to update git submodules, you do so one of three ways:

  1. You can execute git submodule update --init --recursive to update all submodules.
  2. You can also choose to update submodules one by one, by executing git submodule update --init --recursive deps/<first-or-third>/<Repo>. Do not use the --remote option unless you actually want to update to the latest commit.
  3. If you would rather pick a specific commit or branch to update a submodule to then cd into the submodule directory for that dependency and execute git checkout <branch name or commit>. The main dependency you might want to update from time to time is deps/first/Unreal.

Credits

All contributors since the project became open source: https://github.com/UE4SS-RE/RE-UE4SS/graphs/contributors

  • Original Creator The original creator no longer wishes to be involved in or connected to this project. Please respect their wishes, and avoid using their past usernames in connection with this project.
  • Archengius
    • UHT compatible header generator
  • CasualGamer
    • Injector code & aob scanner is heavily based on his work, 90% of that code is his.
  • SunBeam
    • Extra signature for function 'GetFullName' for UE4.25.
    • Regex to check for proper signature format when loaded from ini.
    • Lots and lots of work on signatures
  • tomsa
    • const char* to vector<int> converter
      • tomsa: Idea & most of the code
      • Original Creator: Nibblet support
  • boop / usize
    • New UFunction hook method
  • RussellJ
    • Blueprint Modloader inspiration
  • Narknon
    • Certain features and maintenance/rehosting of the project
  • DeadMor0z
    • Certain features and Lua updates/maintenance
  • OutTheShade
    • Unreal Mappings (USMAP) Generator
  • DmgVol
    • Inspiration for map dumper
  • Buckminsterfullerene
    • Rewriting the documentation, various fixes
  • trumank
    • Lua bindings generator, various fixes, automation & improvements
  • localcc
    • C++ API

Thanks to everyone who helped with testing

  • GreenHouse
  • Otis_Inf
  • SunBeam
  • Motoson
  • hooter
  • Synopis
  • Buckminsterfullerene