How to Use Nucleus Co-Op
Once Nucleus Co-Op is installed and you have a handler for your game, this guide covers everything you need to know — from the basic play flow to advanced configuration like custom layouts, hotkeys, dual monitor setup, and using Nucleus with Plutonium or tModLoader.
Basic Play Workflow
Every session in Nucleus Co-Op follows the same core steps regardless of which game you are playing:
- 1
Launch Nucleus Co-Op as Administrator
Right-click NucleusCoop.exe and select Run as administrator. This is required by most handlers to properly hook into game processes and manage window positioning.
- 2
Select Your Game
Your installed games appear in the left sidebar. Click a game to open the configuration screen. If you do not see your game, click Add New Games to download and install the handler.
- 3
Read the game setup notes
Below the game cover image you will see notes from the handler developer. Read these carefully — they contain critical information specific to that game, such as whether Steam must be open, whether the game needs to be in windowed mode first, or if additional mods are required.
- 4
Assign Input Devices
Press a button on each controller (or move each mouse/keyboard) to make the input icons appear in the Nucleus UI. Drag each icon to the screen section it should control. Click the corner icon on each section to change its layout.
- 5
Click Play
Press the arrow button, configure any handler options that appear, then click PLAY. Wait for the game instances to launch, resize, and position — this can take 30–60 seconds for some games.
- 6
Connect In-Game
Once both instances are running, follow the game setup notes to connect them — usually by one player hosting a LAN game and the other joining. The exact steps vary by game.
Nucleus Co-Op Hotkeys & Shortcuts
These keyboard shortcuts work while Nucleus Co-Op is running. All shortcuts can be customized in Nucleus Co-Op settings under the Hotkeys tab.
| Shortcut | Action |
|---|---|
| End | Lock / unlock input (required for multi-keyboard/mouse handlers) |
| Ctrl+Q | Close Nucleus Co-Op and all running game instances |
| Ctrl+R | Resize all game instances without closing the app |
| Ctrl+H | Unfocus all game instances (equalizes FPS across instances) |
| Windows + B | Alternative unfocus shortcut |
| Alt+Tab | Switch focus away from game instances to equalize performance |
The End key is the most important shortcut to remember. When using handlers that support multiple keyboards and mice, pressing End after instances launch locks all input so each keyboard/mouse only controls its assigned instance.
Custom Resolution & Window Layout
If your game instances appear stretched or at the wrong size, adding custom resolutions to your monitor profile fixes this. When playing 2-player split on a 1920×1080 monitor, each instance needs a 960×1080 (side by side) or 1920×540 (top/bottom) resolution. Without these custom resolutions, some games default to the nearest standard resolution and appear stretched.
Add custom resolutions through your GPU control panel — Nvidia Control Panel, AMD Software, or Intel Graphics Command Center all have this option. If your panel does not support it, use the free Custom Resolution Utility (CRU). Common resolutions to add for a 1920×1080 screen:
1920×540960×1080960×540640×10801280×720640×7201280×360640×360 Your Windows Display Scale must be set to 100% for Nucleus to position windows correctly. Higher scale settings cause offset positioning bugs. You can change scale at Settings > System > Display > Scale.
Using Nucleus Co-Op with Dual Monitors
Nucleus Co-Op supports multi-monitor setups. When you have two monitors connected, both will appear in the Nucleus layout editor, allowing you to assign one full game instance per screen rather than splitting a single screen. This is the best experience for 2-player co-op — each player gets a full monitor.
For multi-monitor setups, make sure both monitors are set to the same resolution for consistent window sizing. If one monitor is 1920×1080 and another is 2560×1440, some games may have difficulty rendering at different resolutions simultaneously. Match resolutions in Windows Display Settings before launching.
Using Nucleus Co-Op with Plutonium
Plutonium is a free platform that provides enhanced servers and mod support for Call of Duty games (BO2, BO3, MW3, WaW). Nucleus Co-Op has dedicated handlers for Plutonium versions of these games. To use Nucleus with Plutonium:
- Install Plutonium and ensure the game launches correctly standalone.
- In Nucleus Co-Op, search for the Plutonium-specific handler (e.g., "Black Ops 2 (Plutonium)").
- Point Nucleus to the
plutonium.exeexecutable. - Follow game setup notes — Plutonium handlers usually require Plutonium to be running and logged in first.
- Assign controllers and click Play as normal.
Nucleus Co-Op on Steam Deck
Nucleus Co-Op is a Windows application and does not run natively on SteamOS. However, some users have had success by installing Windows on a Steam Deck via SD card or dual boot. When running Windows on Steam Deck, Nucleus Co-Op works the same as on any Windows laptop. Performance will be limited by the Steam Deck's APU, so only lighter games are recommended for split-screen use.
There is no official Linux or Proton compatibility for Nucleus Co-Op as it depends on Windows-specific APIs. If you need split-screen on SteamOS, consider Steam Remote Play Together as an alternative.
Nucleus Co-Op with tModLoader (Terraria)
tModLoader is the official Terraria mod platform. Nucleus has a dedicated tModLoader handler that allows modded Terraria split-screen. Point the handler to the tModLoader.exe instead of the vanilla Terraria executable. Both instances will launch tModLoader and connect via LAN. Make sure both instances have the same mods enabled and that your mods are compatible with multiplayer.