How to Install Nucleus Co-Op

System Requirements

Step 1: Download Nucleus Co-Op

Go to the official Nucleus Co-Op GitHub releases page at github.com/SplitScreen-Me/splitscreenme-nucleus/releases and download the latest NucleusApp.zip. Do not download the "Source code" zip files — those are for developers only.

Step 2: Add a Defender Exclusion

Before extracting Nucleus, protect its folder from false-positive deletions:

1. Open Windows Security from the Start menu.
2. Go to Virus & threat protection > Manage settings.
3. Scroll down to Exclusions and click Add or remove exclusions.
4. Click Add an exclusion > Folder.
5. Create a new folder at C:\NucleusCo-op and select it.

Step 3: Extract to C:\NucleusCo-op

Copy the downloaded NucleusApp.zip into your new C:\NucleusCo-op folder. Right-click the zip file, go to Properties, and click Unblock if the option appears.

Extract using 7-Zip (free download at 7-zip.org). When prompted for a password, enter: nucleus. Do not use the default Windows extraction tool as it can cause extraction errors.

Step 4: Launch NucleusCoop.exe

Inside the extracted folder, double-click NucleusCoop.exe. If Windows shows a SmartScreen warning, click More info then Run anyway — this is expected for unsigned open-source applications. If you receive a "Win32Exception: the operation was canceled by the user" error, right-click each .exe file in the Nucleus folder and accept any UAC prompts.

For most handlers, you should also run NucleusCoop.exe as Administrator (right-click > Run as administrator). This is required for certain system-level operations Nucleus performs when managing game windows and input hooks.

Step 5: Download and Install a Game Handler

A handler is a small configuration file (.js or .nc) that tells Nucleus exactly how to launch and connect multiple instances of a specific game. Without a handler, you cannot use a game with Nucleus. Handlers are created by the community and hosted on the SplitScreen.Me Game setup library.

In the Nucleus Co-Op interface, click Add New Games and search for your game. If a handler is available, click Install or Download Handler. Nucleus will then ask you to locate the game's .exe file — most Steam games are at C:\Program Files (x86)\Steam\steamapps\common\[GameName]. Some games store the main executable in a bin or binaries subfolder.

Alternatively, download the .nc handler file from hub.splitscreen.me, then in Nucleus click the Extract a Handler icon and select the file.

Step 6: Assign Inputs and Launch

Select your game from the Nucleus sidebar. The UI will show available input devices — controllers will light up yellow when you press a button, keyboards/mice when you move or type. Drag each input device icon to the screen section you want it to control.

Click the screen layout icon in the top-left corner of each section to change the arrangement (horizontal, vertical, quadrant). When you have assigned all inputs, click the Play button. Nucleus will launch the game instances, resize the windows, and arrange them automatically.

Controller Setup

Nucleus Co-Op works best with native XInput controllers. Here is a quick reference for different controller types:

Installation FAQ