Co-op mod for Grand Theft Auto III

Liberty City, together.

CoopIII hooks the retail gta3.exe directly. No modified binary, no recreation: the real game, with up to 8 players.

Download Setup View on GitHub Join Discord

Windows · needs GTA III v1.0

Launcher

v0.1.3

Pre-launch checks

All clear

gta3.exe is v1.0 retail
ASI loader found dinput8.dll
CoopIII.asi installed scripts\CoopIII.asi
CoopIII.ini found

Check again

Join a server

Co-op only runs when GTA III starts from here. Your name and server are saved to CoopIII.ini.

Your name 4 / 23

noxx

Server address

192.168.1.40

Port

2001

Ask whoever runs the server. The default port is 2001.

Game folder

C:\Games\GTA3

Browse

Start GTA III

Joins 192.168.1.40:2001 as noxx.

Still being built

Networking, the roster, vehicles and combat work: players see each other walk, drive, ride along and fight.

Read the roadmap

Features

The real game, played together

Everything in the repo was written from scratch. What you bring is your own copy of GTA III.

Up to 8 players

A dedicated server relays everyone’s movement, cars and chat. Anyone can run one; friends join with an address and a name.

Keeps your mod stack

Ships as a single .asi loaded by Ultimate ASI Loader, built to live alongside SilentPatch, Mod Loader and CLEO.

Single player stays untouched

Co-op only switches on when the game starts from the CoopIII launcher. Start it any other way and it’s plain GTA III.

Gallery

In the city

Meet up after dark, take to the streets, and see your crew in the same Liberty City.

Two players in their cars on a foggy Portland street at night

Two players beside their cars in Harwood — Meet after dark Pull up with your friends and turn a quiet street into your own meetup.

Two friends standing together on a Liberty City street — Side by side Your friends are right there in Liberty City, not just on the other end of a chat.

Server

v0.1.3

Server

Running

Listening on UDP port 2001 · 8 slots · protocol v6 · up 1:12:40 · in-game 12:40

Address to share 192.168.1.40:2001

Stop server

For friends outside your network, forward UDP port 2001 on your router.

Players

3 / 8

0
noxx Driving vehicle 3
38 ms
1
marta On foot
44 ms
2
kiko On foot
162 ms
3 Open
4 Open
5 Open
6 Open
7 Open

Rules

Friendly fire Off

Wanted level Per player

Mission fails on death On

Options

Console

All Players Chat

21:29:04 [coopiii] listening on 2001, 8 slots

21:31:47 [coopiii] noxx joined (slot 0, net 1)

21:33:12 [coopiii] marta joined (slot 1, net 2)

21:35:40 [chat] marta: meet at the docks

21:36:02 [coopiii] vehicle 3 claimed by noxx (model 90)

21:36:25 [chat] noxx: on my way

21:44:18 [coopiii] kiko joined (slot 2, net 4)

21:58:51 [coopiii] rejected peer 3 (reason 1: bad version)

22:02:09 [coopiii] kiko left (slot 2)

22:03:30 [coopiii] kiko joined (slot 2, net 5)

22:03:41 [chat] kiko: sorry, router died

22:17:26 [coopiii] vehicle 6 claimed by marta (model 110)

22:31:08 [chat] marta: parked it by the bridge

Keep the session running Host the city yourself, see who is online, and keep an eye on every connection.

How it works

Three steps to co-op

The Setup and the launcher do the checking for you, so a wrong game version never gets as far as a crash.

01
Run the Setup

Installs CoopIII and the Essential Pack into your GTA III v1.0 folder.
02
Start from the launcher

It checks the game, then starts GTA III with co-op switched on.
03
Join a friend

Type the server address and your name. The default port is 2001.

Roadmap

Where it’s at

The world is in and campaign co-op has reached tier 1. A complete, playable campaign remains the long goal.

M1 See each other In progress
M2 Vehicles In progress
M3 Combat Working
M4 The world Done
M5 Portland Done
M6 Staunton Island Planned
M7 Shoreside Vale Planned
M8 Make it usable Planned

Bring a friend to Liberty City.

Grab the Setup now and start playing.