Feel free to join the development Discord server here.
This is a multiplayer mod for Cities: Skylines II. Join your friends and build a city together!
The mod is experimental. Back up your saves before hosting or joining, and expect bugs while development continues.
- Cities: Skylines II (PC Version: Steam, XBox, Gamepass)
- All players should run the same version of the mod. A host can allow a different build with the own-risk compatibility override, but incompatible network protocols are always rejected and mixed builds can desync or crash.
- Players should also have matching gameplay DLC. Radio Station DLC are unaffected. Learn how to disable DLC: Disabling DLC
- There are no mods currently working.
- (Internet play only: Set up TCP Port Forwarding)
The easiest way is through Paradox Mods: find the mod, add it to an empty playset, enable it, and restart the game if Cities: Skylines II asks you to.
- In the mod settings, set your player name and choose the host port, password, max players, LAN-only mode, and world re-sync interval.
- Click Multiplayer on the main menu, then Host Game.
- Pick a connection. Steam Relay needs no setup and works if everyone owns the game on Steam. Direct connection syncs faster but the host has to make their port reachable, and it is the only option on Xbox App, Microsoft Store and Game Pass copies.
- With Steam Relay, copy the join code and send it to your friends. For direct connection, see Direct connection.
- Choose Load World for an existing city or Create World for a new one. If you use an existing save, make a backup first.
- Finish the game's normal world selection. The multiplayer session starts automatically once the city is fully loaded.
- If a city is already open, you can still start hosting from the in-game Multiplayer panel or the mod settings.
- Click Multiplayer, then Join Game from the main menu, or open the Join tab in the mod settings.
- Enter the host address, port, your player name, and the password.
- Click Join Session.
- Wait while the host's city downloads and loads — larger cities take longer. The dialog closes itself once you're in.
- City looks out of sync? Run
/syncin chat, or click Sync World Now in the mod settings. Clients pull a fresh save from the host; the host refreshes every connected player. - Can't join (protocol mismatch)? You and the host are on different mod versions. Update to the same build.
Check out Troubleshooting or the complete Error and Warning Reference for more issues.
- The host is authoritative, and clients download the host's world when they join.
- The mod checks for matching DLC and version numbers before letting users connect. Find a list of white-listed DLC here.
This mod and its source code are licensed under the CS2 Multiplayer Mod Non-Commercial License. The license allows personal use, modification, and contributions to this project, but it does not allow commercial use, paid redistribution, or publishing clones/rebranded forks as someone else's project.
Contributions are welcome as long as they follow this repository's license. Keep attribution intact, submit changes through this project, and do not publish paid, monetized, or rebranded copies of the mod.
This project is not affiliated with, endorsed by, or sponsored by Colossal Order, Paradox Interactive or Iceflake Studios.