Importing mods into Cities: Skylines transforms a standard municipal simulator into a sandbox where you control every transit line, zoning law, and architectural asset. While the Steam Workshop handles most installations automatically, manual imports and custom third-party files require precise directory placement and dependency management to keep your saves from breaking.
Whether you're moving custom assets from external sites or troubleshooting missing script dependencies, getting your mod loadout right protects your save files and cuts down game load times. Let's look at how to structure your files, manage dependencies, and troubleshoot the common crash loops that happen when mods clash.
Understanding Where Mods Go
Cities: Skylines separates custom content into two main categories: assets and code mods. Mixing up where these files live is the single most common reason custom content fails to show up in the game's content manager.
Assets include buildings, vehicles, parks, and tree props. These files usually end in .crp and belong in your game's asset directory rather than the plugin folders. When you download a custom skyscraper or intersection pack, you're getting a .crp file that the game reads directly into its asset catalog during startup.
Code mods alter how the game functions, changing traffic AI, economy mechanics, or camera controls. These require script loaders like Harmony or BepInEx to inject code into the game engine while it runs.
Your local user data folder holds these directories on Windows by default:
- Asset folder path:
AppData\Local\Colossal Order\Cities_Skylines\Addons\Assets - Mod folder path:
AppData\Local\Colossal Order\Cities_Skylines\Addons\Mods
Manual Installation vs. Steam Workshop
The Steam Workshop remains the simplest way to manage your collection because it handles downloads, updates, and automatic file placement. When you click subscribe on a Workshop item, Steam places the mod folder containing its ID number straight into your Steam library workshop content directory (steamapps\workshop\content\255710).
However, external sites like Nexus Mods and specialized community hubs host custom content that requires manual installation. Follow these steps when installing manual files:
- Download the archive file, which is usually zipped as a
.zipor.rar. - Extract the archive using a utility like 7-Zip, making sure you don't nest folders incorrectly.
- Open your file explorer and locate your local
Cities_Skylines\Addons\Modsdirectory. - Drag the unzipped mod folder directly into the Mods directory, ensuring the main folder containing the mod's
.dllfile sits directly insideMods. - Launch the game, open the Content Manager from the main menu, and enable the mod under the Mods tab before loading a city.
Managing Dependencies and Core Frameworks
Many advanced mods rely on shared code libraries to function correctly. If you install a traffic management overhaul or a complex zoning tool without its required dependencies, the game will throw errors or disable the mod automatically.
Harmony is the most common dependency framework for Cities: Skylines script mods. It patches game methods at runtime so multiple mods can modify the same base game code without conflicting. Always check the description page of any script mod you manually download to see what version of Harmony or other core libraries it requires.
When a mod breaks after a game update, it's usually because the underlying game code changed while the mod's hook remained outdated. Keeping your core frameworks updated prevents cascading errors across your entire mod list.
Troubleshooting Common Mod Errors
Even with careful file placement, conflicts happen. Recognizing error codes and visual glitches saves hours of frustration.
Missing dependency errors show up when a required .dll file isn't present in your directory structure. If the game's content manager lists a mod in red text or fails to initialize it, check the output log file located at AppData\Local\Colossal Order\Cities_Skylines\output_log.txt. Opening this text file in a text editor reveals the exact line where a script failed to load or threw a null reference exception.
The white texture bug occurs when custom asset bundles fail to load or reference missing texture maps. If buildings or vehicles appear as solid white blocks, you're likely missing an asset dependency or running an outdated version of a shared material loader.
To isolate a crashing mod, disable your custom content entirely, then re-enable items in small batches of five. Launch a test city after each batch to catch the conflicting file immediately.
Frequently Asked Questions
Why won't my manually installed mod appear in the Content Manager?
The mod folder is likely nested incorrectly inside your directory. Make sure the folder containing the mod's .dll file is placed directly inside your Addons\Mods folder, rather than putting the outer zip container or an extra subfolder there.
Do mods affect saved game files?
Yes. Once you save a city with certain script mods enabled—especially traffic or economy overhauls—removing those mods can corrupt your save file or cause the city to crash upon loading. Always make a backup copy of your save files before testing new gameplay mods.
Can I use mods on offline mode?
Steam Workshop mods work offline as long as they are fully downloaded and synchronized on your local machine before you disconnect from the network. Manual mods don't require an active internet connection at all.
How do I safely clean out broken mods?
Unsubscribe from broken items on the Workshop, then manually check your local Addons\Mods and Addons\Assets directories to delete leftover folders. Clearing your game's cache folder can also resolve lingering file conflicts after a mass cleanup.
