A free co-op mod for GTA IV: The Complete Edition

GTA IV
Co‑op

Play Niko's story, The Lost and Damned and The Ballad of Gay Tony with up to three friends. The host plays their own save; friends drop in as their own characters for every mission, chase and shootout.

Download v0.9.1 beta Windows installer · GitHub

A fan's side project, made for fun. Who made this?

3 stories 4 players join from the phone no port forwarding
Whiz21:47
Multiplayer

Start a co-op game from your own save. Your friends join with a 6-digit password over Steam.

The whole story with your friendsRide with the Lost MCRace your crew across Liberty CitySkydive together over Liberty CitySame song on the radio in every carRevive your crew before they bleed outBeat your friends at pool, darts and bowlingThe FBI might drop in The whole story with your friendsRide with the Lost MCRace your crew across Liberty CitySkydive together over Liberty CitySame song on the radio in every carRevive your crew before they bleed outBeat your friends at pool, darts and bowlingThe FBI might drop in

The story,
together

The missions play exactly as Rockstar wrote them, on the host's game, and everyone is in them: the same enemies, the same cars, the same cutscenes, at the same moment.

Missions

Every fight is everyone's fight

Enemies, allies and mission cars are there for all of you, and they shoot, take cover, chase and crash on every screen. Objectives, markers, timers and dialogue show up for everyone.

All three stories

Niko, Johnny or Luis

GTA IV, The Lost and Damned and The Ballad of Gay Tony all work. Skydives hand everyone a parachute; races show everyone the course.

Regroup

Nobody gets left behind

When a mission jumps somewhere new, your friends land next to you, or in a free seat of your car.

Cutscenes

Watch together

Everyone watches the cutscene, and friends can still walk around inside it.

Downed

Get me up

Take a bad hit on a mission and you go down instead of dying. A friend can pick you up.

Your character

Look like you

Pick your own outfit, hat and glasses. Everyone sees it.

Radio

Same song, every car

Every station plays the same track for everyone. Whoever's in the front seat picks it.

Downtime

Your turn, your character

Bowling, darts, pool, air hockey, golf, arm wrestling, cards and races: everyone plays as themselves with their own score. Then get drunk together.

Friendly fire Off / On / No aimReviveShared payRadio syncWeather syncFriend blipsCutscene cameraShared trafficInvasions

Optional: invasions

The FBI
is coming

Turn invasions on and, while you're on a mission or wanted, another group of up to four can crash your game as FBI agents, out to take down the host.

  • No respawns for the agents, only each other's revives.
  • Down every agent and you've beaten the invasion.
  • Take out the host and the FBI wins.
  • Up to eight players in one city.

Get
playing

Everyone who plays needs their own copy of GTA IV: The Complete Edition on Steam.

1. Install

Download and run the installer. It finds your game and sets everything up, including TJGM's FusionFix pack if you don't have it. Tick Radio Restoration: it's strongly recommended.

2. Host

Load your save, open the phone, go to Multiplayer › Host and pick a 6-digit password.

3. Join

Your friends open their phone, choose Multiplayer › Join and type in the same password.

Something broke?

Phone › Multiplayer › Save logs (or Ctrl+Shift+L) puts a zip on your Desktop. If the game won't start, the installer's Collect logs button does the same. Attach it to a GitHub issue with what happened.

Why TJGM's pack? It gives the game a good, stable base, and it's the only setup the mod is tested with. Other mods haven't been tested and may not work alongside it. I'm not affiliated with TJGM or the makers of FusionFix: I just consider their work a baseline for the game, and the installer fetches it from their official downloads to save you getting it separately.

Testers wanted

Version 0.9.1 beta. It has only been tested on one PC against a test bot so far, so real games with real friends are what it needs most. Expect rough edges. Found a bug? Open an issue on GitHub and attach the log zip.

Who made
this

I've wanted a co-op campaign for GTA IV since I was 11 years old. This is a side project I made for fun with spare AI tokens: Anthropic's Claude wrote the code and I steered it. I'm not a reverse engineer and don't claim to be, just a fan of the game. I am a good programmer, though, and the project is built on solid fundamentals: a clean structure, every change reviewed, and automated tests that host, join and switch stories on the real game. The source is on GitHub if you want to look under the hood or help out.

Tested where possible

Automated tests host, join and switch between all three stories on a real game. They don't catch everything, which is why testers help so much.

Safe for your game

Your saves are never changed when you join someone, and the installer backs up anything it replaces. Uninstall puts it all back.

Clean

No DRM tampering. Extras like FusionFix come from their official downloads.

Fails gently

Where it can, if something in your game isn't the way the mod expects, it switches that feature off and says why instead of crashing.