Casualties: Unknown lists single-player on Steam. Co-op comes from the community Casualties Together mod, not an official multiplayer mode.
Current compatibility matters
| Mod release | Author’s stated target |
|---|---|
| v5.5.0 — 10 November 2026 | Full game v1.0 |
| v5.4.0 — 9 November 2026 | Demo v7.0.1 and full game v1.0, with an unfinished full-game port warning |
| v5.3.1 — 8 November 2026 | Demo v7.0.1 |
The v5.5.0 author says the full-game update is not thoroughly tested, although they report completing it from start to end. That is an author report, not our playtest or a guarantee of a stable session.
Before downloading
Identify whether each player owns the full game or uses the separate demo. Read the selected release’s target and assets. The repository README still links the demo as a prerequisite, so the versioned release notes are essential for the newer full-game branch.
What changes in full-game co-op
The v5.5.0 notes add character selection: everyone chooses a character and uses Ready Up before the host starts. They also document continuing synchronization limitations, including unreliable crystal effects in Crystalline Hollow.
Follow installation for the documented folder layout, and use connection checks if the expected multiplayer interface does not appear.
Sources & version notes
Reviewed against the primary sources below. Version-dependent details are identified in the article; these procedures have not been personally playtested.
- Official Steam store: Casualties: Unknown (2026-11-11 checked)
- Casualties Together author installation and features (2026-11-11 checked)
- Casualties Together versioned releases, including v5.5.0 (2026-11-10 / checked 2026-11-11)
Compiled from public sources. We have not personally played or tested these procedures. Check your installed build and its tooltips when details differ.