Casualties Unknown multiplayer

The base game is single-player: Steam lists it that way, and players on the forum report that the developer does not plan to add co-op. reported Casualties Together is the mod almost everyone uses, with 143,012 Nexus downloads and 1,166 endorsements on 9 November 2026. confirmed

Does Casualties Unknown have official multiplayer?

No. The Steam page lists Single-player and Family Sharing only. confirmed A forum regular summed it up as the developer leaving co-op to modders, and another noted that it is a community mod you use at your own risk. reported Treat any future official support as unannounced: nothing in the official posts through 15 October 2026 mentions it.

How do you install the Casualties Together mod?

These are the steps from the mod’s own page. confirmed

1. Get the game or the free demo on Steam, and download BepInEx 5.4.23.5 x64 and the mod’s zip from its Nexus files tab.
2. In Steam, right-click the game and choose Manage > Browse local files.
3. Unzip BepInEx into that folder, the one with the game’s .exe.
4. Unzip the mod, open its folder, and move the contents into the same game folder.
5. Go back to Steam and press Play. New multiplayer buttons should appear in the main menu.

On Linux, add this to the game’s launch options: WINEDLLOVERRIDES="winhttp=n,b" %command%. confirmed The general mod install guide covers what to check when BepInEx does not load.

Going back to solo play does not need an uninstall. Use the Deactivate MP Mod button under Settings > General. confirmed

What changes when you play together?

Co-op is not just the solo game with a friend added. The mod alters survival rules so a shared run stays playable. confirmed

Feature	What it does
Steam lobbies	Host and invite through Steam
Voice chat	In-game voice with effects applied to it
Point	Middle mouse button marks a location
Heal others	Right-click to interact with and treat another player
Share warmth	Standing close shares body temperature
CPR minigame	Bring back a player in cardiac arrest
Carry	Move an incapacitated player
Spectator	Watch after you die
Sleep	Disabled while the mod is active
Hunger and thirst	Drain more slowly than in solo
Unchipped mode	Set per player

Most of these can be adjusted from the in-game console, and the mod can run as a dedicated server, though its page says that is not truly headless. confirmed

Because sleeping is off, plan around energy and mood differently from a solo run. The sleep guide only applies to single-player.

What are the limits of the mod?

The mod’s author is direct about this. There is no client prediction, no network ownership, no deterministic randomness and no anti-cheat. confirmed In practice that means a laggy host affects everyone, and you should only play with people you trust.

Save problems are the most common complaint worth planning for. A separate mod, Multiplayer Inventory Load Fix, exists because equipped items could fail to restore when loading a multiplayer save, showing “item too far” errors. confirmed

Which add-ons work with Casualties Together?

Add-ons usually need to be on every machine, and a skin mod needs the host to have it too. confirmed

• CatPatch: hugs for a mood boost, sprays and more host controls, with 24,754 downloads. confirmed
• Multiplayer skins: replace how your character looks and sync it to others.
• Simple QoL: works alone or with the co-op mod on both host and client. confirmed
• Prosthetics: works if both host and client have it and its requirements, and its author warns of bugs. confirmed

Why can’t my friends join?

Work through these before reinstalling anything. They follow the mod’s install requirements and the general BepInEx checks.

1. Everyone is on the same game build and mod version. The mod was last updated on 8 November, one day before the full release.
2. BepInEx sits beside the game’s .exe, not inside an extra nested folder.
3. Add-on mods match between host and client.
4. The multiplayer buttons appear in the main menu. If they do not, the mod has not loaded, so the problem is the install rather than the network.

Where do you get help?

The mod has its own Discord, linked from its Nexus page, and that is the place for bug reports. Report problems there with your mod version, and try the run without other add-ons first. The best mods list shows what else is popular once co-op is running.