Casualties: Unknown WikiUnofficial field guide
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Official Steam page

Mods and multiplayer in Casualties: Unknown

Short answer

Casualties: Unknown is single-player only; the Steam page lists no co-op. Multiplayer exists only as a community mod (Casualties Together, by Krokosha) built on BepInEx 5.4. Mods are hosted on Nexus Mods under the game's old name, Scav Prototype. Many demo-era mods may not work on 1.0, so check each mod's version.

Applies to Release 1.0 (Nov 9, 2026) Sources checked

Multiplayer

The official game has no multiplayer. The community multiplayer mod, usually called Casualties Together or KrokMP, lets players share a run. Several add-on plugins depend on it, such as late-join fixes, and they must match across the lobby. The community guide notes that the multiplayer mod adds CPR, which restarts a stopped heart at about 100 compressions per minute. Community wiki Players

How to install mods

  1. Back up your save folder (see save location).
  2. Download BepInEx 5.4.x for Windows x64 and extract it into the game folder, so winhttp.dll sits next to CasualtiesUnknown.exe.
  3. Start the game once, then close it. BepInEx creates its folders.
  4. Put each mod's DLL in BepInEx/plugins, plus any library it requires.
  5. Check the mod page says it supports 1.0. To uninstall, remove the plugin or rename winhttp.dll.

Only download from pages you trust. Mods are executable code. Stick to Nexus Mods pages with comments and recent updates.

Mods on Nexus include quality-of-life tweaks, unlock-all-characters mods, container sealing, custom skins and co-op. The developer expects modders to expand systems such as prosthetics. Official

Mobile, console and other ports

There is no official mobile, Switch or Xbox version. The game runs on Steam Deck and Linux through Proton. See the FAQ.

Questions

Is Casualties: Unknown multiplayer?

No. The game is single-player. Co-op is only available through a community mod.

How do you install mods?

Most mods are BepInEx 5.4.x plugins. Install BepInEx into the game folder (next to CasualtiesUnknown.exe), run the game once so it creates its folders, close it, then put mod DLLs in BepInEx/plugins. Follow each mod page, as some need helper libraries.

Does everyone need the same mod version?

For the multiplayer mod, yes: mod pages say every player in the lobby must run the same plugin and multiplayer mod version.

Do mods disable achievements?

This is not documented officially. Console commands outside the sandbox do disable achievements, and mods that rely on them may too.

Sources

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Console commandsOpen the console, the useful commands, and what disables achievements.FAQPrice, platforms, Steam Deck, controller, demo, length and content warnings.