As mods play an important role in the Cities: Skylines landscape, CSM aims to support the most important mods for the multiplayer experience.

A few features are provided to make this possible. They will be explained in the following chapters.

When joining or hosting a game, a panel provides information on mod support status. The following states are possible:

• Supported: The mod is explicitly supported and should work perfectly
• Known to work: No explicit support is necessary, the mod is known to work
• Unsupported: The mod is known to cause problems, you should disable and/or uninstall the mod for a flawless multiplayer experience
• Unknown: Nothing is known about the mod, it may work but it might also cause problems. If you encounter any issues, disable and/or uninstall the mod.

Some mods are also classified as client-only mods that don't affect the multiplayer experience, although this property is only known for a defined set of mods.

To support more complex mods with multiplayer, they can use our API to implement the synchronization logic. More information can be found here: Modding API

To provide a more seamless multiplayer experience, installed mods and assets are compared when joining other games. The following must be equal:

• Mods with explicit multiplayer support
• The built-in mods of Cities: Skylines (like Unlock All)
• Any installed assets

Other mods are not considered for now as they might work just fine even if it is unknown if they are supported.

An overview of supported mods can be found here: Supported mods