Quickstart Guide

Prerequisites

IW4x is not a game on its own. It requires Call of Duty: Modern Warfare 2 (2009) to be installed.
If you do not own the game yet, please first buy and install it via Steam.

Important Compatibility Notice

As of 2025, Call of Duty: Modern Warfare 2 is also available via the Microsoft Store.
Please note: IW4x is not compatible with this version. Only the latest Steam version of the game is supported.

Additionally, we frequently see issues caused by pirated copies, including bugs and crashes.
We do not support pirated versions and will offer no assistance for them.

Iw4x needs to be installed in the same directory where Call of Duty: Modern Warfare 2 is installed.
Usually, the path to this directory is:

Windows

 C:\Program Files (x86)\Steam\steamapps\common\Call of Duty Modern Warfare 2

Linux

 $STEAMLIBRARY/steamapps/common/Call of Duty Modern Warfare 2

MacOS

 ~/Library/Application Support/Steam/steamapps/common/Call of Duty Modern Warfare 2

Finding your Modern Warfare 2 installation

If you have trouble to find the install directory, you can use your Steam Library as help:

1. Open Steam and go to your LIBRARY

2. Right-click on Call of Duty: Modern Warfare 2 (2009) - Multiplayer

3. Select Manage > Browse local files

Verifying Game Integrity

Before installing IW4x, it’s a good idea to verify the integrity of your game files through Steam.
This prevents errors such as ERROR: Could not find zone 'code_pre_gfx_mp.ff', when launching IW4x.

1. Open Steam and go to your LIBRARY

2. Right-click on Call of Duty: Modern Warfare 2 (2009) - Multiplayer

3. Select Properties…

4. Select Installed Files

5. Click the button Verify integrity of game files

Steam will check that all game files are intact and properly installed. If it finds anything missing or corrupted, it will automatically re-download the necessary files.

Installing IW4x

Once you’ve located the Modern Warfare 2 game directory, you are ready install IW4x.
The simplest way is by using the IW4x launcher, which will download and install all required files automatically.

1. Download the launcher using one of the buttons below:

   Download for Windows Download for Linux

2. Move it into your Modern Warfare 2 directory

3. Double-click the launcher to start the installation

Windows protected your PC

Windows may display a warning the first time you run iw4x-launcher.exe.
This happens simply because the file isn’t commonly seen on Windows systems (not because it’s unsafe).
It’s completely normal behavior and the launcher is safe to use.
If you see the warning, you can safely click on More info and then Run anyway.

(And yes, the warning can be removed, but it requires a Microsoft code-signing certificate, which costs a lot of money.)

Using the Launcher

Note

We recommend using the launcher every time you play IW4x.
It will automatically download any updates, verify your installation, and start the game.

Once you’ve installed IW4x, you should see the following files in your game directory:

<FileTree>

• Call of Duty: Modern Warfare 2
  • iw4x/
  • iw4x.exe
  • iw4x-launcher.exe
  • … other files and folders </FileTree>

Command Line Arguments (CLI)

The IW4x launcher is powered by a Command Line Interface. Instead of editing a configuration file, you customize the launcher’s behavior by passing arguments to it.

The most common way to do this on Windows is by creating a shortcut:

1. Right-click iw4x-launcher.exe and select Create shortcut.
2. Right-click the new shortcut and select Properties.
3. In the Target field, add your desired arguments to the very end of the line (outside the quotes).

Example: Loading a Mod

If you want to play offline against bots using the Bot Warfare Mod, you need to pass specific arguments to the game. You can do this using the --game-args flag.

Your shortcut’s Target field would look something like this:

"C:\...\Call of Duty Modern Warfare 2\iw4x-launcher.exe" --game-args "-disable-mod-unloading" --game-args "+set fs_game mods/mp_bots"

Now, every time you use this shortcut, the launcher will ensure your files are up to date and then automatically start the game with the Bot Warfare mod loaded!

Available Launcher Options

Here is a list of common arguments you can use to configure the launcher:

Argument	Description
--game-args "<arg>"	Additional arguments to pass to the game executable. Can be specified multiple times.
--prerelease	Opt-in to pre-release (beta) updates. Use this to test upcoming features before they are marked as stable.
--skip-launch	Skip launching the game after updating/installing. The launcher will perform all operations but exit without starting the game.
--game-exe "<file>"	The game executable to launch. (Defaults to iw4x.exe).
--path "<dir>"	The installation directory for the game files. (Defaults to the current working directory).
--jobs or -j <num>	The number of parallel download jobs to run. (Defaults to 99).
--no-self-update	Skip the automatic launcher self-update check.
--self-update-only	Only check for and apply launcher updates, then exit. Does not update game files.
--help	Show the help message and exit.
--version	Show version information and exit.

(For advanced users: You can also easily pass these arguments using a .bat file or directly via your terminal/command prompt).