Install Nucleus Co-op · Docs

Nucleus Co-op is portable: there is no installer to run. You unzip it into a folder and start NucleusCoop.exe. Where that folder lives matters more than you'd think.

Download

Get the latest release from the download page or straight from the GitHub releases. Take the release archive, not the "Source code" zip: that one is for developers.

Pick the right folder

Create a folder at the root of a drive, for example C:\NucleusCo-op, and keep it out of these places:

Program Files and Program Files (x86): Windows protects them, and Nucleus needs to write next to itself.
Your user folder, Desktop, Documents or Downloads: some handlers create separate Windows users, which can't reach your own folders. OneDrive-synced folders cause trouble too.
Inside a game's folder: never put Nucleus Co-op among the files of a game you want to play.

Some handlers also need Nucleus Co-op on the same drive as the game. If your games are on D:, use D:\NucleusCo-op. That drive must be formatted NTFS: exFAT and FAT32 drives can't hold the symbolic links most handlers use.

Unzip

Unblock the archive
Right-click the downloaded zip, choose Properties, tick Unblock if it's there, then OK. Files that keep the "downloaded from the internet" mark can be blocked by Windows later.
Add an antivirus exclusion
Add your Nucleus Co-op folder to the Microsoft Defender exclusions (or your antivirus' equivalent) before you extract. See the note below for why.
Extract into the folder
Extract everything into C:\NucleusCo-op. 7-Zip is the most reliable tool for it. If the archive asks for a password, it's nucleus.
Start NucleusCoop.exe
The first start checks the Visual C++ runtimes and Microsoft Edge WebView2, and offers to download what's missing. Accept, let them install, and start Nucleus Co-op again if it asks.

"Windows protected your PC"

If SmartScreen shows this when you start NucleusCoop.exe, choose More info, then Run anyway. Unblocking the zip before extracting (step 1) usually prevents it.

Administrator rights

Nucleus Co-op runs as a normal user. A few handlers need administrator rights: their notes say so. Use Settings › About › Restart as administrator for those sessions only.

What's in the folder

Folder or file	What it holds
`NucleusCoop.exe`	The app
`handlers\`	Installed handlers: one `.js` file per game, sometimes with a folder of extra files
`content\`	The copies of each game that Nucleus prepares for every player, and your library
`game profiles\`	Saved profiles: layouts, options, who plays where
`Settings.ini`	Your settings
`debug-log.txt`	The log, when debug logging is on
`docs\`	The readme files, with the handler reference of your version
`utils\`	Emulators and tools that handlers use

Each player's own data (saves and settings of games that use the Nucleus environment) lives outside the app folder, in C:\Users\<you>\NucleusCoop.

Update

Handlers update from the app: when the hub has a newer version, the library shows Update to vN on the game. Settings › About › Handler updates checks every game at once. Updates keep your profiles and settings.

Nucleus Co-op itself: download the new release and extract it into a new, empty folder. Don't extract it over the old one. To keep everything, copy these from the old folder into the new one before the first start:

handlers\
game profiles\
Settings.ini
content\userprofile.json (your library)

Or skip the copy: Found on this PC finds your Steam and Epic games again in a minute. When the new version works, delete the old folder.

Uninstall

Delete the Nucleus Co-op folder. If you also want to remove the players' data, delete C:\Users\<you>\NucleusCoop, but check first that no save you care about lives there (Saves and profiles). If a handler created Windows users (their names start with nucleusplayer), remove them in Settings › Accounts › Other users on Windows.