Cities: Skylines

Cities: Skylines

125 ratings
[Beta] CSM - Cities: Skylines Multiplayer
File Size
1.630 MB
Nov 6, 2018 @ 10:36am
Jan 12 @ 2:41pm
6 Change Notes ( view )

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[Beta] CSM - Cities: Skylines Multiplayer

Cities: Skylines Multiplayer (or CSM for short, or Tango - the codename) is a mod that provides a client-server multiplayer experience in Cities: Skylines. This is the official Steam Workshop listing for this mod located on GitHub. For the latest and greatest code, you should continue installing manually, but this listing will be updated every few days with the latest build.

See to help develop the mod or report any bugs and issues. We also have a Discord server located here:, and a Patreon located here:

Please Note: Due to the early state of this mod, not everything works. You can see an example on what is synced on the GitHub.

Before posting a question, pelase check out the FAQ here:


1. If hosting locally (within your network), check that your firewall is open, it hosting over the internet, you may need to port forward. By default CSM runs through port 4230.
2. Either start with a blank world, or open a world and PAUSE the game. If you are playing an existing world, you need to send a copy to every client, (this process will be automated in the future). It's recommended that you start with a blank world.
2.5 Worlds are located here: %LOCALAPPDATA%\Colossal Order\Cities_Skylines\Saves
3. When in game, click the "Show Multiplayer Menu" button and then click "Host", enter your name and an optional server password.
4. You should see a message saying the server has started.

1. Create a new world of the same type, or open the copied world from the host.
2. When in game, click the "Show Multiplayer Menu" button.
3. Click "Join Game" and enter the IP address, your name, and optional server password.
4. You should see an error message saying that you have connected (and the server should also see the same message).

See the GitHub for known issues.
Popular Discussions View All (2)
Jan 2 @ 1:52pm
Multiplayer Won't Work
Chill Productions
Dec 6, 2018 @ 6:06pm
Can't find the multiplay menu button
Cr4ck Horse
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repak52 Jan 15 @ 2:45pm 
^^V Jan 9 @ 10:47pm 
Still have some problems but great work
christian treholt Jan 6 @ 4:15pm 
@Ricky @Robert if you are using our newest github version districts are also synced, the steam version will soon be updated
Robert7301201 Jan 6 @ 4:02pm 
@Ricky According the the GitHub page, Zones are synced, districts are not.
Ricky Jan 6 @ 3:45pm 
Are zones/districts synchronized?
TomLA Jan 6 @ 5:45am 
I am having the same problem as @S=X. The game runs ok for a while and then one of the players developes the error below:

Array index is out of range. [System.IndexOutOfRangeException]

No details[i/]

It means that whenever someelse manipulates the map in anyway they get an error popup which they have to click away before continuing to play. It then also spams you with these errors if you click play on the time slider. Which makes the game unplayable.

Also found the untilities (especially power lines and water pipes) make the area they are placed in very laggy. Not sure if that is a bug with the game or the mod but I have not experienced it in single player.

Big fan of the idea that I could build a city with a friend so I hope you find this information useful so we can all enjoy a bit of multiplayer. :)
S=X Jan 3 @ 12:29am 
Array index is out of range. [System.IndexOutOfRangeException]

No details
Naryc Dec 25, 2018 @ 8:05am 
great idea, but there were no sync between energy, water und population. so i had 5 people with no water and energy and my partner had all houses with people and power...

But we will keep an eye on your work. if there is an option to support...:goodthumb:
Engie Dec 24, 2018 @ 6:51pm 
terrain editing dosent sync yet :(

but love the mod hope you develop it more
Bobbystrahler Dec 20, 2018 @ 3:18pm 
Nice Mod. Works fine in Vanilla. But does it also work with Mods?