Should I use IW4x or IW4x (mm)?

Choose IW4x if you want to browse and join community-hosted dedicated servers, where each server sets its own rules and mods. Choose IW4x (mm) if you would rather use matchmaking and play with friends through a built-in friends list and party system. Both are multiplayer clients for Call of Duty: Modern Warfare 2 (2009), both support mods, and you can play with friends on either one — the difference is how you find a game.

The core difference

IW4x and IW4x (mm) are two versions of the same client, each built around a different way to play.

Pick IW4x if you want server choice

IW4x is centred on community-run dedicated servers. Because each server can have its own rules and mods, this is the version to use when you care about where you play — a particular server's settings, its mod lineup, or its regular player base.

Playing with friends works by coordination rather than an in-client invite: you join the same server, or you host a server yourself and have them connect to it.

Pick IW4x (mm) if you want matchmaking and parties

IW4x (mm) is built around matchmaking, with friends and parties available directly in the client. If your priority is adding friends, inviting them to a party, and getting into a game together without picking a server, this is the simpler path.

You give up per-server rule and mod selection as the organising principle, though mods are still supported.

What both versions share

• Mods are optional on both. You can install either client and play without touching mods at all.
• You can play with friends on both. The mechanism differs — party invites on (mm), shared or self-hosted servers on IW4x — but neither locks you out of group play.
• Same base game. Both are multiplayer clients for Modern Warfare 2 (2009).

System requirements

The published baseline applies to the client; server hosting has its own requirements.

Client

Server

If you plan to host for friends rather than just join, check the server row — the upload and port-forwarding items are the ones that most often block people.

Still deciding?

Answer one question: do you want to choose a server, or do you want the client to find the game for you? Server choice, custom rules, and mod-driven communities point to IW4x. Fast grouping with friends and no server browsing point to IW4x (mm). Since mods and friend play exist on both, neither choice costs you those features.

IW4x is open source, and development happens publicly on GitHub — you can read the code and follow changes, and the project points contributors to an open issue or the contributor guide as a starting point. Earlier client builds are kept in a release archive for reference.