RimWorld was designed as a single-player survival story, but the community long ago proved that a colony is twice as fun with a friend beside you. The Multiplayer mod by Zetrith turns the game into a true co-op — from controlling one colony together to running separate colonies on a shared map with trade and wars. Here is how to set it up without wasting your evening on desyncs.
What the Multiplayer mod can do
The free Multiplayer mod supports up to fifteen players at once. It works in two modes: a shared colony — everyone controls the same colonists and sees the same base — and a split mode where each player has their own people on a shared map, economy and event cycle. The mod syncs not only actions but the game's random events too: raids and weather are identical for everyone.
What you need
- The same game version for everyone — currently RimWorld 1.6; check the mod page.
- The same mod list on the host and every joining player. The mod can pull the host's mod list, but the files must exist locally.
- For the host — a stable connection: their machine runs the simulation for everyone.
- Without Steam — a VPN network (Radmin VPN or Hamachi) or a forwarded port.
Installing the mod
Download the mod from its page and install it the usual way — the full walkthrough is in our RimWorld mod installation guide. Once enabled in the mod list, a new Multiplayer button appears in the main menu. The Harmony library is required, as with most mods — keep it enabled.
- 1Install and enable the Multiplayer mod (and Harmony) in the mod menu.
- 2Launch the game — a Multiplayer button appears in the main menu.
- 3Make sure your friends have the same mod and game versions.
Hosting a game
- 1In the main menu, click Multiplayer → Host.
- 2Pick a new colony or an existing save.
- 3Configure options: auto-pause when menus open, game speed limits.
- 4Invite your friend: via Steam — pick them from the friends list in the mod overlay; without Steam — share your VPN IP.
- 5Once they join, their cursor appears on your map.
Direct IP connections use the port listed in the mod settings. Inside one VPN network (Radmin/Hamachi) no port forwarding is needed — only the IP.
Joining a friend
- 1Enable the same mod set as the host.
- 2Main menu → Multiplayer → Join.
- 3Pick the host from the list (Steam) or enter their IP (Direct Connect).
- 4Wait for the sync — from a few seconds to a minute with a large mod list.
Compatibility with other mods
Not every modification plays nice with the network mode. Libraries, content and performance mods are usually fine: Harmony, Performance Fish, RocketMan. Mods that deeply rewrite the UI or add their own simulation loops can cause desyncs. Golden rule: run your mod build solo in host mode for a couple of minutes before inviting friends.
Harmony
by Brrainz
Harmony is the shared patch library used by many RimWorld mods. This mod provides Harmony to the game so other mods can depend on one common version instead of each shipping their own copy. For play
Performance Fish
by Michael
Performance Fish patches RimWorld's core methods for better framerates and tick times with identical behaviour - big lategame gains, made by Bradson, safe alongside RocketMan.
Common problems and fixes
- Desync — trim your mod list, remove suspicious mods, update the mod to the latest version.
- A friend cannot see the host — check identical game and mod versions; without Steam, verify the VPN network.
- Crash on join — almost always a mod conflict: compare the mod lists one by one.
- Lag at 3x speed — the host can use TicksPerSecond and simulate fewer colonists.
- Saving in multiplayer — the host saves as usual; keep all mods enabled on the next launch.
Done — the colony is now shared. Find more mods for your build in the RimWorld catalog, and get the load order right with our load order guide. Happy hunting!