The primary goal for Cities Skylines 2 late-game optimization is Geometric and Volumetric Culling. Late-game lag is often caused by the game trying to calculate detailed light-scattering (Volumetrics) and high-fidelity shadows for every single building and vehicle. This configuration focuses on stripping away the heavy atmospheric simulations to prioritize the simulation clock.
File Location
The settings for Cities Skylines 2 are stored in a .coc (Colossal Order Container) file. It is a JSON-like format.
%AppData%\..\LocalLow\Colossal Order\Cities Skylines II\Settings.coc
Technical Configuration (The 2026 “Metropolis” Template)
Open Settings.coc with Notepad. Look for the qualitySettings array and update these specific keys. These values are tuned to reduce the draw-call count, which is the main culprit for late-game stuttering:
{
"qualitySettings": [
{
"enabled": false,
"@type": "Game.Settings.VolumetricsQualitySettings"
},
{
"level": "Low",
"distance": 25.0,
"@type": "Game.Settings.LevelOfDetailSettings"
},
{
"enabled": false,
"@type": "Game.Settings.DepthOfFieldQualitySettings"
},
{
"shadowQuality": "Low",
"terrainCastShadows": false,
"@type": "Game.Settings.ShadowQualitySettings"
},
{
"maxLightCount": 1024,
"geometryCacheLimit": 512,
"strictGeometryLimit": true,
"@type": "Game.Settings.GraphicsSettings"
}
],
"maximumFrameLatency": 3,
"vSync": false
}Parameter Breakdown:
- maximumFrameLatency “3”: This is the “secret sauce” for 2026 performance. It allows the CPU to queue frames ahead of the GPU. While it adds minor input lag (negligible in a city builder), it smooths out the massive “sim-speed” hitches during sunset or high traffic.
- geometryCacheLimit “512”: Late-game cities have massive amounts of unique geometry. Increasing this from the default (often 256) reduces the “stutter” when moving the camera across a dense skyline.
- strictGeometryLimit “true”: Forces the engine to stop rendering objects that aren’t immediately visible, saving precious CPU cycles on culling.
- VolumetricsQualitySettings “enabled”: false: Volumetric clouds and fog are the most taxing settings in the game. Disabling them can gain up to 15-20 FPS in large cities.
Strategy for 2026 Late-Game Stability
Beyond the file tweaks, these strategies are essential for 1M+ population cities:
- The “Taxi Depot” Rule: A known engine quirk in 2026 is the pathfinding bloat caused by Taxis. In late-game, Delete all Taxi Depots. Use specialized Bus and Subway lines instead; the taxi dispatch system generates thousands of unnecessary CPU queries that slow the simulation to a crawl.
- Disable “Virtual Texturing” Notifications: In the settings, ensure you wait for the “Virtual Texturing” to finish before unpausing. If you build while this is processing, it can lead to a permanent memory leak for that session.
- Resolution Scaling: In 2026, DLSS 3.5 / FSR 3 is native. Set Dynamic Resolution Scale to “Constant” and use a minimum scale of 70%. This ensures the GPU load stays low so the CPU has more “room” to handle the AI.
- Remove “Homeless” Entities: A common late-game bug involves homeless Cims congregating in parks and slowing the simulation. Periodically deleting parks or using a “Homeless Fix” mod is recommended for cities over 300k.
Key Performance Parameters
| Parameter | Recommended Value | Impact |
| Level of Detail (LOD) | Low (25%) | Drastically reduces the “Teeth/Hair” CPU overhead. |
| Volumetrics | Disabled | The single biggest FPS gain (15-20 FPS). |
| Shadow Quality | Low | Essential for reducing VRAM usage in dense cores. |
| Frame Latency | 3 | Smooths out 1% low framerate stutters. |
Frequently Asked Questions (FAQ)
Why does my simulation speed slow down but my FPS is high?
This is a “CPU Bottleneck.” Your GPU is ready to render, but your CPU is struggling to calculate the pathfinding for thousands of Cims. Lowering Animation Quality and LOD helps alleviate this.
What is “Geometry Cache Limit”?
It is the amount of RAM/VRAM dedicated to storing building models. In late-game, increasing this to 512MB or 1GB (if you have 32GB+ RAM) stops the “black building” glitches during fast panning.
Does disabling Fog really help?
Yes. In the Settings.coc, turning off Fog and Global Illumination removes the complex light-bounce calculations that happen for every single skyscraper window.
My settings reset after every update!
Colossal Order updates often overwrite the .coc file. Save a copy of your optimized code as Settings_Backup.txt so you can quickly paste it back after a patch.
Conclusion and Expected Results
By disabling Volumetrics and increasing the Geometry Cache in your Settings.coc, you are refocusing your hardware on the simulation rather than the “atmospheric fluff.” You can expect more consistent simulation speeds, the elimination of “Black Screen” geometry glitches, and a significantly smoother camera experience when flying over your 500k+ population metropolis.