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Unreal Mods FAQ


What is a Mod

Modification or "mod"

A mod is a non-commercial add-on to a game, usually freely available, that alters gameplay in some way. Which means Infiltration would be considered a mod, because it gives you different weapons and changes gameplay as a result, but a player model like SpaceMarine is not considered to be a mod, because it just changes your appearance without altering the "rules" of Unreal.


A Unreal player model is an add-on consisting of a 3D mesh made from triangles, one or more skins for that mesh, and the Unreal Script necessary to use it in the game to represent you, another player or a bot. Models built in to Unreal include Male Players, Female Players, Nali Players and Skaarj Players, while add-on models include Messiah, Bug, etc......


A skin is a texture (image) designed to be wrapped round the surface of a particular 3D mesh. For example, Male3 Player skins include Bane, Dante, Dregor and Kringe. Add-on skins are available for all the basic Unreal models and for most add-on models.


A mutator is a piece of UnrealScript run by a Unreal server to alter or "mutate" gameplay. For example, a mutator can replace all weapons with something else (Instagib), alter physics (Low Gravity), and so on. Many mods are implemented as mutators.


A UMOD is a standard installer format used by Unreal, which comes in a file with the extension ".umod". The name stands for Unreal Module. It is understood by the installer "Setup.exe" found in the \System\ folder on Windows versions of Unreal, and by third-party installers on Mac and Linux Unreal.

ZIP file

Most mods, models and skins are distributed as a ZIP file containing a UMOD file. A ZIP file is a compressed file containing other files, and takes less time to download than its uncompressed contents would. Before you can use the contents of a ZIP file, you need to "unzip" (decompress) them, using a program like Winzip (Windows), Stuffit Expander (Mac), or the zip and unzip programs from Info-Zip (any platform, but they're particularly suitable for Linux).
All mutators will have a ".u" file and a ".int" file. Some complex mutators may have more than one ".u" or ".int" files. No matter, just put the ".u" and ".int" files in your Unreal System Folder. Some mutators may also include additional texture, sound and/or music files... just follow the extension grid below to see where those additional files need to go.


Unreal patches are official updates released by Epic Games to fix bugs, prevent multiplayer cheating and occasionally even add features. Patches are supplied as an executable file (no extra software is required, you just download the patch and run it). You should download and install Unreal patch 224f or 225f if you plan to run a server .

Installation and uninstallation

UMOD files (*.umod)

On Windows Unreal these should be easy - the Unreal install associates them with Unreal\System\Setup.exe, so Windows users with a correctly installed copy of Unreal should be able to just double-click the .umod file and follow the instructions (if asked for your Unreal folder, always choose the base folder, such as C:\Unreal, and not a subfolder like C:\Unreal\System).

To uninstall, open your Unreal \System folder and manually select the mod(s) you want to uninstall and delete them. For example, the Infiltration mod installs a bunch of files that start with "Infil". Don't uninstall "Unreal" unless you want the whole of your Unreal folder to disappear!

Linux users can install UMODs using UMODPack, a set of Perl scripts containing command-line and GUI installers. Usually the command-line version (umod) is more reliable than the X GUI (xumod) when dealing with badly-made or Windowsish UMODs (spaces in filenames).

You can use Debian or just use whatever package management tool you prefer (dselect, aptitude, apt-get...) to download and install the package "umodpack". It's in the stable distribution as of Debian 3.0.

See man umod for more information.

Mac Unreal users should already have a UMOD installer made by Westlake Interactive. I've never used Mac Unreal, but I assume it's similar to the Windows installer.

Individual files (*.utx, *.int, *.u, *.unr, *.uax, *.umx etc.)

If you downloaded a ZIP file containing individual files (many maps and a few skins are still packaged this way), the files go in subfolders of your Unreal folder. Some maps have additional files which also need to be installed... these could be additional textures, music, sounds, etc. All of those files also go in specific folders, and need to be moved there in order for the map to work properly. Here is a list of the extensions you will encounter, and where to put the files:

To uninstall, you'll have to remember what you installed and delete the files yourself. First, locate all of the system files associated with the mod.  The easiest way to do this is to open your Unreal System folder and find a file installed by the mod.  This shouldn't be too hard.  For example, the Infiltration mod installs a bunch of files that start with "Infil".

Once you have found one of the mod's files, select it, then sort the folder by date.  This will group all of the files you installed or were created on a specific date, effectively grouping all of the mod's files together.

Move the files to the Trash.

Move the mod's .ini files from your Unreal folder to the Trash.

That mod should never bother you again.

Why doesn't it work?


All mods should come with a text or HTML file containing the instructions. Read it.

If the mod is packaged as a UMOD, make sure you entered the correct Unreal path when you installed it. All UMODs should be installed to the base Unreal folder (like C:\Unrea), not to a subfolder (like C:\Unreal\System).

If the mod is packaged as a collection of individual files with extensions like *.utx, *.unr and *.u, make sure you put them in the correct folders (above).

No mod (this includes skins and models) will work in multiplayer unless it is installed on the server. See ServerPackages below for details of how to set up mods if you intend to run a server.


If you're wanting to use a custom player model on your server, be aware that you need to install it and add it to your server packages.

Linux users need to edit $HOME/.loki/unreal/System/User.ini, where $HOME represents your home directory - Linux Unreal is a real multi-user app and has separate configuration files for each user.


If you're trying to use skins for a custom model (any model except (Male/Female) (Skaarj/Nali) you need to install the model first. Unreal is not like Half-Life or Jedi Knight where all skins include the model. For example, to use the MessiahSkin you need to have the SPMessiah model.

How do I make my new skin work in the single-player Mode?

You can't. Custom models and skins only work in botmatches or multiplayer. Multiplayer only works if the server has the skin and has placed it in their ServerPackages list.

Making skins

How do I make skins for the Unreal Player models?

You'll want to extract the original skins to use as a template. To do this, open up UnrealEd, open the texture browser and select the file you want to edit and open it. Right-click on each texture and export it. Open the texture in a graphics editor like Photoshop, from there you can make the changes you want.

Server Packages

The Unreal game engine maintains a list of allowed packages for the server. These determine what models and skins the server is allowed, among other things.

If the server doesn't have enough server packages, players will be unable to use custom skins and models, unless the serveroperator adds more server packages to their .ini.

Every player (client) joining the server must have all the server packages to play on your server. If they have the same package, fine. If they have a different package with the same name, they will not be able to join the server due to a "Version Mismatch" error. If they don't have the required package, they will be made to auto-download it (this is slow and frustrating for all except the smallest packages).

How do I change my server packages?

Unfortunately, you can't do this while Unreal is running, you will need to close down Unreal if it's running already. Open up your Unreal/System.ini with Notepad or text editor, Do not use Word and look for a heading [Engine.GameEngine].

Under this heading you should see several lines in the format, I.E. ServerPackages=Female1skins. Delete any server package you are not using, leaving the default server packages intact, now add similar lines for each package you will be using. The bit after the equals sign should be the name of the package file without the extension, so to add the SPMessiah bot to your server, you would need to add SPMessiah.u and MessiahSkins.utx to your server packages.


Now anyone who plays on your server will see the bot and skin.

Important note: If you copy and paste server packages or any other settings from a website, be careful - most web browsers will add a space after each line. You need to delete these extra spaces for Unreal to work.

Correct: "ServerPackages=Female1skins"

Wrong: "ServerPackages=Female1skins " (note the space after SomeMod)

Linux users need to edit $HOME/.loki/unreal/System/Unreal.ini instead, where $HOME represents the home directory of the user who will be running the game. If you have a multi-user Linux box, everyone who'll be running a server needs to edit their own ServerPackages; if you have a "daemon" userID which will be used to run dedicated servers, you need to edit its copy of the INI file too.

What needs to be in my server packages?

Whatever happens, you need the following for Unreal to work:


Maps and their resources don't need to be in the server packages - the server automatically assumes the current map and all its resource files are included.

Models, skins, gametypes, mutators and voicepacks do all need to be in the server packages.

Special thanks to Simon McVittie for writing this FAQ

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