Cities: Skylines

Cities: Skylines

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Performance Tuning Guide - Cities Skylines
By aubergine18
This guide covers every known way to boost performance of the game...
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Paradox Launcher update seems to cause IPT2 / TLM to lag
If your game has started slowing to a crawl recently, try disabling Improved Public Transport mod, or Transport Lines Manager mod.

Also, never have both those mods active at same time as they are not compatible with each other.
Introduction
Updated: January 2020
If you've been directed here because your game is running out of RAM and started crashing, skip this intro and go straight to the RAM, pagefile and Loading Screen Mod sections below.

About this guide
I've been updating this guide for almost 5 years - it contains everything I've found on making the game run faster.

The guide follows a logical progression: Launching the app -> loading a save -> in-game. It tackles the various issues at each stage with mods, hardware and system tuning. Don't just jump to the in-game section though, go through each step in sequence. For example, getting your page file set up (part of 'launching the app' stage) will improve loading performance and in-game performance. Likewise, the Loading Screen Mod (part of 'loading a save' stage) will help reduce strain on your graphics card and RAM, which in turn improves in-game performance.

Expectations...
When it was first developed, CO's team was small (just 5 developers). The game uses an old version of the Unity game engine which isn't "thread-safe" - that means it can't properly take advantage of modern hardware without rewriting the entire game for a modern game engine - buying faster hardware is not going to give you as much performance boost as you might expect.

As your city grows, potato computers will struggle to get above 20fps while gaming rigs will struggle to get above 40 fps. So you need to be prepared for that. That being said, we are now starting to see FPS Boosting mods which tackle key bottlenecks in the game code and potentially give big performance increases, but more on that later.
Launching the app
Updated: January 2020
This section no longer relevant due to paradox launcher being added in January 2020. Will update when there are more reliable ways of deleting it, but for now see this topic and this guide

Reduce network traffic
When you first launch the app, there's a lot of communication with the Steam servers, especially if you have lots of workshop subscriptions. These two mods help you get to the main menu faster:
https://steamcommunity.com/sharedfiles/filedetails/?id=812107110
https://steamcommunity.com/sharedfiles/filedetails/?id=1665106193
Note: You can run in offline mode, but it disables all mods - and yes, there are ways to work around that limitation, however many mods rely on game APIs that are only available when they are treated as Workshop mods (which require online mode).

Delete unwanted save games
On potato computers (very low spec), deleting unwanted save games weirdly makes app launch a little quicker and sometimes even gives slight performance increase while in-game. You can delete unwanted saves via: Main Menu > Content Manager > Savegames
- RAM and page file
Updated: January 2020
If you don't have enough RAM and page file, the game will lag and might even crash.

RAM
This game eats RAM like crazy, especially if you start adding DLC and workshop content. RAM usage peaks when loading and saving games. Assets (buildings, vehicles, roads, etc) eat much more RAM than mods.

The Steam store page for C:SL states the game will run in 4GB RAM - that's a joke. Even the vanilla game, with the content added by free updates, will struggle to run in 4GB. It will be a laggy mess.
  • For the base game to run well, you need at least 8 GB RAM.
  • If you start adding DLC and workshop, you ideally need 16 GB RAM or more.
If you don't have enough RAM the game has no choice but to start moving stuff out of RAM and in to the page file on disk. Disk (even super-fast NVMe M.2 SSD) is always significantly slower than RAM.

More RAM = less swapping to disk = faster performance.

Faster RAM is better, but only if your CPU can handle it. So check carefully before buying more RAM to make sure it's going to work well with your CPU.

AMD Ryzen users: B-Die finder[benzhaomin.github.io] + OC calculator[www.overclock.net] yw (:

ProTip: Use memtest86[www.memtest86.com] to check for faulty RAM. It is operating system independent and vastly superior to any mem testers that come with your operating system. Faulty RAM causes random problems (like broken textures) and crashes.

Page file (a.k.a. 'swap file' or 'virtual memory')
Note: This game will always use the page file, even if you have loads of RAM.

Anything that doesn't fit in RAM goes in to the page file; if the page file isn't big enough to accommodate it, the game will crash. In addition, the game engine tries to push anything it isn't currently using in to the page file, and your operating system will do the same.

On Windows, it's critical that you set the page file size manually. The old version of Unity engine pushes stuff to page file in small chunks rather than one big chunk, and that caues lag during loading screen and can even cause crashes[support.microsoft.com].

Set the minimum size equal to 16384 MB or, if you have enough disk space, 32768 MB. The maximum size should be set to the same or more.
  • Windows: See Windows 10 or Windows 7, 8 or 10[www.thewindowsclub.com].
  • Linux: Try Zram[en.wikipedia.org] and zswap[wiki.archlinux.org], in that order. But do not use cryptswap as it causes problems (thanks @daniel.mantione and @flo for this info).
  • Mac: Use Boot Camp to run Windows or Linux partition, then see above.
Tip: Check you have plenty of free disk space. If you run out of disk, it could cause the pagefile to shrink and will almost certainly lead to crashes (eg. if not enough room for log file or temporary data or save games, you get crashes)!
- CPU and Operating System
Updated: May 2020
The main performance bottleneck is the primary CPU core.

CPU
Most of the game runs in the "main thread" on the primary CPU core. It's a huge bottleneck and is mainly due to the old version of Unity game engine (as mentioned in Introduction section, it's not "thread-safe").

The faster your primary CPU core, the better the game will run:
  • You ideally want 3.8GHz or faster for "gaming rig" performance.
  • Intel CPUs tend to have the fastest primary CPU cores (as of January 2020).
  • However: If you use the computer for lots of other stuff, AMD CPUs are generally better value for money and beat Intel on almost everything except primary core speed.

Anti-virus apps sometimes put excessive strain on CPU, particularly Avira Antivirus.

Operating System
The game works best on Windows, because it tends to get faster driver updates (particularly for graphics card).

On Windows 10, use 'Balanced' or 'Performance' power profiles, even if you have AMD CPU; test to see which gives best results. See also: How to speed up Windows 10 (ignore stuff about mouse speed, that actually slows down C:SL).

On a Mac? Use Boot Camp[support.apple.com] to install a Windows partition and run the game on that. Sounds crazy, but it will be faster than the native Mac version of the game on OS X.

I've never played it on Linux, so can't help with that.
Starting or Loading a Game
Updated: January 2020
Faster loads = biggest "quality of life" improvement

I cannot stress this enough: Out of every improvement I achieved, shrinking game loading times had by far the biggest impact on my enjoyment of the game - way more than increasing in-game fps (we'll get to that later, don't worry). I used to wait up to an hour for a save to load, now I wait less than 2 minutes. It means I can dip in to the game any time I want, rather than having to plan a session in advance.

The loading process
There are four key stages which can be represented by the loading bar:
  • 0-50%: Assets are laoded (vanilla first, then DLC, then workshop). Loading Screen Mod (see later) makes it hugely faster, having more assets makes it slower.
  • 50%-95%: Asset textures get processed in to texture atlasses, and some mods start initialising. More RAM and faster CPU makes it faster, having more assets and mods makes it slower.
  • 95%-100%: All of the AIs and game code initialises, and lots of mods do bulk processing. The progress bar and spinning circle will stall because this part of loading is so intense the screen can't update. A fast CPU and more RAM make it faster, grind mods make it hugely slower.
  • In-game: Shortly after your city loads and appears on screen, lots of mods do their final stage of initialisation causing lots of lag and stuttering. Pausing the game on load helps them finish that work faster and helps clear any backlog of background processing tasks.
The next few sections of the guide focus on making the loading process much faster, but note that many of those things also improve in-game performance, particularly on potato computers.
- Loading Screen Mod (LSM)
Updated: January 2020
Reduce RAM and VRAM usage = faster loads and slightly faster gameplay.

Loading Screen Mod (LSM) is a "must have" mod regardless of your computer specs:
https://steamcommunity.com/sharedfiles/filedetails/?id=667342976
It reduces strain on your RAM, page file, VRAM (graphic card RAM) and massively reduces load times, and often improves performance in-game too. It also has really good error handling features and can generate reports of broken assets.

Example (2500 assets and 110 mods):
  • On my potato PC loading went from 50 minutes → 25 minutes
  • On my new PC loading went from 10 minutes → 2 minutes
  • I saved about 15 GB of RAM too!
If you're not using LSM, just turn everything off and go herd goats in the mountains or something.

Let's look at the main options (more are listed later):
⠀⠀
Load Used / Enabled assets (read carefully)
For hassle-free operation, both of these should be enabled (recommended).

However, if you want fastest possible load and minimum RAM usage, disable "Load enabled assets" but enable "Load used assets". This means only assets already used in the savegame will be loaded, but you will be limited to only those assets while building your city. More info.

Share resources (recommended)
Assets, particularly those in the workshop, have lots of duplicate textures, meshes and materials.

Enable the sharing options for those things and you'll save loads of RAM (often several gigabytes).

Note: Graphics cards with lots of VRAM (2GB or more ideally) can handle more textures (in other words, more assets) without relying on slower motherboard RAM. If you keep adding more and more assets, you will still eventually fill the VRAM and incure peformance issues.

Optimise asset thumbnails (recommended)
This option, when enabled, instantly saves you 1.5 GB RAM or more.

Reporting options (use periodically)
These reports can help you track down missing assets, and also helps to find and remove bloated and broken workshop assets. We'll deal with that later.

Note: Creating reports slows the loading process a little so turn off reports if you're not using them.

Prefab skipping (recommended)
This lets you turn off assets from the vanilla game and DLCs, and can save you huge amounts of RAM. See Prefab skipping guide for details of how to use the feature.

Suppress reporting (recommended)
While loading, you'll see warnings about stuff that's missing. If, like me, you disabled a bunch of stuff, those warnings just clutter the screen and make it harder to spot other issues. To use this feature, load a saved game then go in to LSM mod options and click the button to open the file - then follow instructions at the top of the file.

Safe mode (use to fix savegames)
If you are getting errors in your save games, enable these three options and then try loading your save. If it manages to load, create a new save with a new file name, then exit the game to desktop and then load it up again and it should work fine from that point onwards. See Safe Mode guide for more details.

If the options don't fix your save, then it's likely to be a broken mod or asset. See Finding Broken and Bloated Assets guide for dealing with that. There's also some useful stuff in the TM:PE troubleshooting guides[github.com] that might help.
- DLCs, Mods, Assets
Updated: January 2020
The more you add, the slower the game becomes...

Recommendations
If you overburden your hardware with too many DLCs, mods and assets, the game will grind. But what sort of numbers are we talking about here? It's difficult to quantify, because no two DLCs, assets, mods or computers are alike - but here's a rough guide based on RAM (these values assume you are using Loading Screen Mod to help reduce RAM consumption):
  • 8GB RAM: 100 assets, 5 mods, 1-2 DLCs
  • 16GB RAM: 500 assets, 20 mods, 5-10 DLCs
  • 32GB RAM: 2000 assets, 50 mods, 15 DLCs
  • 64GB RAM: 4000 assets, 100 mods, All DLCs
Obviously, RAM is not the only factor but it's a good reference point. If you have powerful graphics card (with lots of VRAM) you can handle more assets. If you have powerful CPU, you can handle more mods. And, as mentioned later, a fast disk drive helps reduce lag in all aspects of the game.

DLCs
DLCs are official add-ons for the game. Depending on your hardware (particularly RAM and CPU), adding too many can impair performance and even cause crashes.

Radio stations don't cause any problems, as only one track plays at a time. But other DLCs can add huge numbers of assets (particularly content creator packs, and Green Cities).

Tip: You can disable purchased DLCs via Steam Library: Right-click the game in the library and choose "Properties...", then choose DLCs tab. But be careful - some workshop mods and assets rely upon DLCs and might break without them.

Steam Workshop
Content from Steam Workshop can be considered in three main categories:
  • Maps & Map Themes: Only one of each is active per city. In terms of game performance, we can safely ignore these.
  • Mods: These alter the game code (but can sometimes also include assets). You can have potentially hundreds of mods active per city.
  • Assets (everything else): This is content such as buildings, roads, vehicles, etc. You can have potentially thousands of assets active per city.
Nothing will destroy game performance more than you subscribing to crazy numbers of mods and assets, so learn to deal with your subscription addiction!
https://steamcommunity.com/sharedfiles/filedetails/?id=449998850
Some general tips before clicking the Subscribe button:
  • Are you really actually ever going to use this thing?
  • Look at what other users are saying in the comments, and how the author responds to them.
  • Author name is in yellow text, so easy to spot in comments - if the author is still around answering questions, that's a good sign.
  • Good ratings and lots of subscribers is generally a good sign, but not always. There's lots of broken stuff which used to work years ago (hence subscribers and ratings) but no longer works with current version of the game.
  • If there is a yellow "This item is incompatible with Cities: Skylines" banner across the top of a workshop page, DO NOT SUBSCRIBE (or, if you already did, unsubscribe it). It will literally break your game.

Mods
Each mod (generally speaking) adds more workload for your CPU.

The compatibility checker will help you find out if you have any problem mods (it lists any that are laggy, broken, etc):
https://steamcommunity.com/sharedfiles/filedetails/?id=2034713132
You can also check the list of broken and incompatible mods[docs.google.com] (the compatibility checker linked above contains most of that list). Someone tested 50 popular mods to see what effects they had on fps, here's the results.

Tip: You can sort mods alphabetically making them easier to work with using either the Sort Mod Settings mod.

Zombie assemblies
There is a "zombie assemblies" bug in the game engine[github.com] which modders cannot fix: If you have more than one version of a mod subscribed, the game can't differentiate between them, even if you disabled the other versions. That causes weird problems, lag and crashes.

So, when using mods, always remember:
  • If there are multiple versions of a mod, only ever use one version at a time.
  • Completely unsubscribe mods you aren't using, don't just disable them.
  • After making any changes to mod (updating, disabling, unsubscribing), exit the game to desktop to flush zombie assemblies from RAM

Assets
Each enabled asset adds extra load for your RAM and VRAM (Video RAM); even if you don't use it on the map it will still get loaded. And once it's on the map, it will put more strain on your GPU (graphics card).

When choosing assets, consider these things:
  • Good asset authors often specify the number of triangles, texture sizes, etc., for their asset. If they've taken the time to optimise the asset, it's probably a good asset.
  • TM:PE team maintains lists of known broken assets: Buildings[github.com], Vehicles[github.com], Props[github.com], Roads[github.com].
Unsubscribe broken & bloated assets
Removing broken and bloated assets will make the game more reliable and improve performance:
https://steamcommunity.com/sharedfiles/filedetails/?id=1846793796
Disable unwatned assets
Many workshop assets are acutally colleciotns of assets - a single subscription might contain a building and several props, or several variants of a network, etc. You can disable individual assets, even if they are part of a pack, via Main Menu > Content Manager > Assets screen.

This mod will help you browse and filter your asset list: https://steamcommunity.com/sharedfiles/filedetails/?id=814498849
By disabling assets you prevent their mesh (triangles) and texture getting loaded in to RAM (unless something else uses it). That will make loading faster and in some cases will improve visual quality of all other assets of the same type (by avoiding the need to rescale everything smaller to fit that extra texture in the texture atlas).
- Disk Drive
Updated: February 2020
Faster disk = faster loads, less lag during autosave and sometimes faster gameplay

The bulk of disk activity comes from loading the game and assets, saving your city, and the page file that we discussed earlier in the guide. If you run out of disk space, the game will crash.

Drive Type
NVMe M.2 SSD drives are currently the fastest choice, but are very expensive and they have limited lifetime (you'll need to replace them more often). They require a modern motherboard that has the M.2 slot, so you need to check if you have that before buying one. Note that some motherboard/processor combinations will reduce graphics performance (from x16 down to x4) if you install two or more M.2 drives, so always check your motherboard user guide first.

Tip: If you are using a Samsung NVMe drive, install Samsung Magician[www.samsung.com] to improve performance and update drivers.

If you can't afford or use M.2 drives, the next best alternative is an SSD drive. While still quite expensive, they are super reliable and still very fast.

If you can't afford SSD, then try and get a fast SATA drive. These used to be quite slow in the past, but recently they've improved a lot.

Disk Optimisation
Most operating systems include some sort of disk optimisation tool, sometimes called a "defragmenter". It optimises data on your disk in such a way that it can be loaded faster, often prioritising the most frequently accessed files. There are also tools for cleaning up junk files which can save lots of disk space, allowing for larger page file and more workshop content.

On Windows 10, for example, you can use tools such as:
ProTip: Use Ultimate Boot CD[www.ultimatebootcd.com] to check disk for bad sectors (thanks to FireFlowerist[forum.paradoxplaza.com] for the tip).

ReadyBoost
ReadyBoost is a feature of Windows (Vista, 7, 8 and 10) primarily designed for potato computers. It can help overcome some issues assocaited with slow disk drives by caching stuff on faster disk drives. For more information, see Using ReadyBoost in Windows[www.winhelp.us] (Windows Vista, 7, 8 and 10).

Avoid RAM Cache apps
tl;dr: AVOID RAM Cache!

RAM cache apps allow you to store regularly used files in RAM, which makes accessing them massively faster. However, anything that eats RAM is generally bad for this game. While you might get slightly faster loading times, literally everything else will be slower because the game will be starved of its much needed RAM.

Disable log file (not recommended)
As someone who regularly requests log files when tracking down bugs, the thought of this fills me with dread. However, I feel compelled to at least mention the fact you can turn off log file in case it helps anyone; it might save a few seconds on really old, slow computers.

To turn it off, add the following launch option:
-noLog
In-game
Updated: January 2020
Test to see if your changes make a difference

This is probably what most people want form this guide. Before we can start improving performance, it's important to have a way to quantify it so you can check that changes you make are having an effect.

FPS display
The most common way is to monitor "fps" (frames per second). The higher the fps value, the faster the game is running.

Steam has it's own fps display which can be accessed from main Steam settings > In-game section:



Alternatives include:

Close other apps!
Obvious really, but if you have other apps running they will be consuming CPU and RAM resources. So close as may of them as possible. The improvement will be most noticeable on potato computers.

ProTip: You can use Autoruns[docs.microsoft.com] from Microsoft SysInternals to close down unwanted startup tasks.

Gaming mode
Dedicate more system resources to the game:
  • Windows 10: Type "Settings" in to the start bar and then choose "Gaming". In the sidebar click the "Game Mode" link and turn it on. See this guide for more info[www.windowscentral.com]
  • Windows (all versions): Third party app, Razer Cortex Booster[www.razer.com] micromanages system resources to boost game performance. Also, Razer Cortex System Booster[www.razer.com] might be worht a look. There might be some privacy concerns with thrid party apps.
- FPS Booster Mods
Updated: January 2020
Less CPU load = faster gameplay.

FPS Booster mods tackle specific bottlenecks in the game code.

Mini FPS Booster
A simple booster that improves performance of mouse position raycasting, giving 5-15% fps boost.
https://steamcommunity.com/sharedfiles/filedetails/?id=1938493221

Note: A larger booster is under development but not ready yet. It is expected to give up to 30% fps boost.

No gains?
If you don't see any improvement to your framerate with both Loading Screen Mod and FPS Booster mod(s) active, your graphics card is likely the main performance bottleneck of your system. If that's the case, reducing strain on your GPU becomes your primary goal...
- Graphics Card & Settings
Updated: January 2020
Faster graphics = faster rendering = faster gameplay

Fast modern GPUs (eg. anything above GTX 1060) won't usually improve framerate much, because CPU becomes the main bottleneck; but you will get nicer looking graphics, less lag on big resolutions, and be able to use graphics mods more easily.

Use dedicated graphics card
"Integrated Graphics" (like Intel Iris) are not real graphics cards. They are designed for energy saving, not gaming. How do they work? They run on your CPU and use normal RAM. That's like a triple disaster for gaming. Not only will your graphics be weaker (and with less quality) but you just nerfed your CPU and RAM making everything else slower too!

On computers that have both integrated and dedicated graphics, particularly laptops but also some desktops, make sure you're using the dedicated graphics card:
See this guide for some tips on Intel graphics.

Update drivers!
Graphics drivers are getting constant updates by manufacturers to fix bugs and improve performance, so keep updating them.
  • Windows: Update direct from manufacturer website: NVIDIA[www.nvidia.com] (game ready driver recommended), AMD[www.amd.com]
  • Macs: Mac driver updates are less frequent, often they come with operating system updates. However you can sometimes get updated drivers from NVIDIA or AMD websites. If you use Boot Camp to run the game under Windows, however, follow the guidance for Windows above.
  • Linux: I've no idea how Linux handles graphics card updates - if you know please leave comment at bottom of guide and I'll update this section.

Shader Version
Graphics cards have a "Shader version" - it determines what features they provide. You can find what version you have in the game log file; search "Shader version" to find it (usually near top of file).

The game works best with shader version 50 or above.

If your graphics card has lower version, usually version 30, problems can occur - you'll see `d3dll` errors in the log, weird graphics glitches in-game, maybe even crashes. To fix, add the `-force-d3d9` Launch Option (or sometimes `-force-opengl` is better, particularly on older Macs).

Graphics Performance
Make sure your graphics card is running in high performance mode:
  • Windows: Search for "Graphic Settings" in start bar, and under "Graphics Performance Settings" manually add Cities.exe as a 'Classic app', and set it to "High Performance".
  • Apple Mac: From Apple menu, select "System Performance" then "Energy Saver" (the light bulb). Uncheck "Automatic Graphic Switching". (thanks LemonsterOG for this tip!)
  • Linux: Not sure if there is such a feature on Linux - if there is, let me know.

Graphics settings
Access these via Main Menu > Options > Graphics:
  • Set a screen resolution that is natively supported by your graphics card (refer to your graphics card tech specs to find details). If your native resolutions aren't listed, use More Aspect Ratios mod to fix that.
  • Lower screen resolutions generally benefit older graphics cards
  • Disable or reduce shadows - particularly effective on older graphics cards
  • Disable film grain - most effective on old computers or weak graphics cards
  • Reduce graphics quality settings - very effective on potato computers and/or weak graphics cards
Note: VSync can tank frame rate in some hardware configurations. Modern alternatives such as FreeSync (AMD GPUs) or G-Sync (Nvidia GPUs) are much better.

Weather effects
On old computers or weak graphics cards, turning off dynamic weather may give slight performance improvement.

NVIDIA Graphics
GeForce Experience[www.nvidia.com] app recognises the game. You can see recommended settings for your specific NVIDIA-based graphics card and apply or customise them.

NVIDIA Control Panel app (usually accessed from '^' button in system tray) allows you to set additionaal app-specific settings under "Manage 3D settings".

The GTX 770 and older NVIDIA graphics cards are pretty weak and don't fully support DirectX 11. You can often improve reliability and performance on those cards with the `-force-d3d9` (force DirectX 9) Launch Option.

If using Zotac editions of NVIDIA cards, the "Zotac Firestorm" app has some tuning and OC functions.

If you have two NVIDIA cards, you can use the following settings to boost performance of the game (thanks to Shaowdane for this tip):
  • Install Nvidia Inspector[www.guru3d.com]
  • If you haven't used NVIDIA Inspector before, read this guide[wiki.step-project.com]
  • Use these settings for your Cities:Skylines profile:
    • SLI Compatiblity Bits (DX1x): 0x202121F5
    • Nvidia Predefined # of GPUs to use on SLI for DX10: SLI_PREDEFINED_GPU_COUNT_DX10_FOUR
    • NVIDIA Predefined SLI mode on DX 10: SLI_PREDEFINED_MODE_DX10_FORCE_AFR2
- ULOD and Hide It
Updated: January 2020
Reduce strain on GPU (Graphics) = faster gameplay

Ultimate Level of Detail (ULOD)
ULOD was developed to increase level of detail (more strain on GPU), however it lets you do the opposite too!
https://steamcommunity.com/sharedfiles/filedetails/?id=1680642819
Try these settings:
  • Tree LOD distance: 300m
  • Prop LOD distance: 750m
  • Decal prop fade distance: 750m
  • Building LOD distance: Use game default
  • Network LOD distance: 750m
The smaller the value, the faster the game will run. Play around to get your desired balance between graphics quality and performance.

Hide It!
While ULOD reduces complexity of stuff that is shown, Hide It mod allows you to completely remove stuff:
https://steamcommunity.com/sharedfiles/filedetails/?id=1591417160
The biggest gains come from hiding stuff that's very common, such as road-side props, billboards, etc. There's a huge long list of stuff - have a play with the settings to see what works best for you.

Hide It makes a load of other mods listed later in this guide somewhat obsolete. Normally I wouldn't recommend big "do it all" mods like Hide It, but it's just so much easier to use than having dozens of 'fix one thing' mods. Sure, there's a few quirks - at time of writing the clouds and fog removal options aren't working (some issue with Daylight Classic mod?) but here I am, still using it.
- Problematic mods
Updated: January 2020
These mods cause peformance issues

Grind mods
These hugely increase loading time (you wait longer for saves to load):
Laggy mods
These mods cause performance issues in game (lower frame rate, lag, stuttering):
  • CitizenTracker - causes massive fps drop, unsubscribe!
  • Building Anarchy - causes massive fps drop, has some bad bugs, unsubscribe.
  • RealCity - causes up to 20 fps drop, unsubscribe.
  • Climate Control - causes up to 20 fps drop, also some bugs, unsubscribe.
  • Extended Game Options - causes 5-15 fps drop, unsubscribe.
  • Extended Info Panel - causes 10 fps drop, unsubscribe.
  • Telemetry Control - abandonware, causes some fps drop, unsubscribe.
  • More Beautification - causes 10fps drop, and lag when opening panels; unsubscribe. Use Find It instead.
  • Advanced Toolbar - causes a 2-10 fps drop, unsubscribe. Use Resize It! instead.
  • Note: The are several other toolbar mods which also cause lag.
  • Ambient Sounds Tuner - causes up to 10 fps drop :( I really love this mod so I decided to keep it and suffer lower fps lol..
  • Prop Line Tool - 10-15 fps drop during even when tool is not in use. Mod author aware, performance issue is being investigated (August 2019).
  • Rush Hour and Rush Hour II - both have severe performance issues. Use Real Time instead.
  • Custom Light Effects - a game engine bug (which mods can't fix) causes memory leaks, which can be major issue if you are low on RAM. Unsubscribe or exit to desktop often.
  • Network Skins - causes lag. Use the new version, Network Skins 2, currently in beta, which is much faster.
  • Traffic++ (all versions) - obsolete and no longer maintained. Use TM:PE instead...
  • Traffic Manager: President Edition (TM:PE) - I consider this a "must have" mod (Disclosure: I am part of the team developing it) and wouldn't play the game without it. However some of it's features can cause fps drop or lag as it puts extra strain on CPU (pathfinder, AIs, etc). In mod options (see TM:PE wiki for full details[tmpe.viathinksoft.com]), disable any features you don't use, and consider using most basic settings for "simulation accuracy" and "reckless driving". Our team is actively working on improving performance, fixing bugs, etc.
  • 81 Tiles - Game really wasn't designed for this many tiles being active. Causes fps drop and there are still some lingering bugs. More tiles = More slow. If you don't need the edge tiles, use Purchase It! mod instead (you'll get up to 25 tiles with much better performance).
  • Metro Overhaul Mod - causes some strain due to lots of network prefabs (version 9+ seems better). Check how it affects your fps before investing heavily in MOM infrastructure.
  • Clouds & Fog Toggler - causes intermittent fps drop. Try Hide It! or (guessing) Toggle It! mod instead.

Broken and incompatible mods
https://steamcommunity.com/sharedfiles/filedetails/?id=2034713132
- Trees and props
Updated: January 2020
If you spam your city with huge numbers of trees and props, that can cause huge fps drop.

This is particularly true if you are using lots of different tree and prop assets.

For example, if you only have 2 types of tree, that's only two tree textures that your graphics card needs to render the scene. However, if you have dozens or even hundreds of types of tree, then the texture for each one needs sending to your graphics card. That takes time, and if you fill its VRAM it will need to process the scene in multiple batches which takes even longer.

There are many occasions where I've gone crazy with Forest Brush, with like 50 types of tree and shrub, to create diverse foilage across entire mountain ranges. Big fps drop and I had to choose some specific types of tree and remove all of those form the map to revive the frame rate.

Tip: Forest Brush mod can sort items by triangles, etc., and hovering trees in its list shows details about thier complexity. When painting lots of trees, limit to just a few types of tree and minimise the use of any tree that's overly complex.

So try and limit how many tree and prop assets you use; the fewer the better. It's not so much how many times a tree or prop is used (that will still have an effect), but more importantly how many different types of them are used.
- Prop removal mods
Updated: March 2020
If you have weak graphics card, getting rid of unwanted props can boost fps...

As mentioned earlier in the guide, Hide It is a great way to remove lots of clutter from the map and user interface.
https://steamcommunity.com/sharedfiles/filedetails/?id=1591417160
If there's a vanilla or DLC prop you never want to see anywhere, use the "Skip assets" feature of Loading Screen Mod. That way, it won't even get loaded in to RAM = faster loading time

Likewise, if there's a workshop prop you don't ever want to see, you can disable it - even if it's part of another workshop asset that you want to keep. Main Menu → Content Manager → Assets.. then find and disable the props you don't want; they won't even get loaded = faster loading time.

If you've subscribed lots of 'vehicle props' (where an asset creator creates prop versions of their vehicles), a faster alternative might be this mod which converts vehicles (and trees!) in to props - it means much faster loading and guaranteed reduction in RAM as it's reusing the exact same textures, meshes and materials as the original vehicle/tree - just remember to unsubscribe all your old 'vehicle prop' assets first:
https://steamcommunity.com/sharedfiles/filedetails/?id=2033714682
Roads have a load of props, and your map has a load of roads. People have actually taken time to comment saying this helped increase their fps. It's particularly effective on potato computers:
https://steamcommunity.com/sharedfiles/filedetails/?id=1117087491
Removes grass tufts and cliff boulders:
https://steamcommunity.com/sharedfiles/filedetails/?id=547533304
Removes ferry route buoy props:
https://steamcommunity.com/sharedfiles/filedetails/?id=949061920
Remove lots of ugly props from buildings to declutter residential and commercial zones:
https://steamcommunity.com/sharedfiles/filedetails/?id=518456166
Remove pretty much any prop or tree from any building or even whole map (Increases game load time, but can boost in-game performance):
https://steamcommunity.com/sharedfiles/filedetails/?id=878991312
Remember, always test! Use the fps counter stuff at top of guide - if something doesn't improve fps on your computer, ditch it.
- Traffic reduction mods
Updated: January 2020
Limit amount of traffic or types of vehicles. Good for potato computers, and also useful for large cities where you're hitting vehicle, citizen and path unit limits...

These mods make game more realistic and also reduce amount of traffic which can gain you some extra fps, especially on potato computers.

This fills cargo vehicles more completely, meaning you need fewer vehicles to transport your cargo:
https://steamcommunity.com/sharedfiles/filedetails/?id=1721492498
This balances your industry more, and greatly reduces the crazy traffic in farming district:
https://steamcommunity.com/sharedfiles/filedetails/?id=1562650024

You can prevent certain vehicles from spawning, which may help on older computers or weak graphics cards:
https://steamcommunity.com/sharedfiles/filedetails/?id=1548831935
Tip: Use Mesh Info (linked earlier in this guide) to identify bloaty vehicles and prevent them from spawning.

Removing seagulls (they're sort of traffic, right?) can gain you a few extra fps, especially in big cities and on potato computers. Also helps reduce strain on citizen limit:
https://steamcommunity.com/sharedfiles/filedetails/?id=564141599
Removes animals; helps reduce CPU load and also less stuff to render for weak graphics cards. Also helps reduce strain on the citizen limit:
https://steamcommunity.com/sharedfiles/filedetails/?id=1706704781
Gets rid of dead people, freeing up space for the liviing. Reduces number of hearses on the road. Good for older computers:
https://steamcommunity.com/sharedfiles/filedetails/?id=803074771
Even more drastic, get rid of death, garbage and crime:
https://steamcommunity.com/sharedfiles/filedetails/?id=769744928
- Other useful mods
Updated: March 2020
These mods are useful for reducing load for older computers or weak graphics cards...

An extreme way to reduce GPU load is to render the world at a lower resolution (less than 100%) and then scale it up to fit the screen. The graphics will look awful, but it will greatly increase frame rate if your GPU is the bottleneck:
https://steamcommunity.com/sharedfiles/filedetails/?id=812713438
Turning off tree movement may improve fps if your graphics card is weak:
https://steamcommunity.com/sharedfiles/filedetails/?id=1388613752
Turning off the clouds and fog can help with weak graphics cards. Although some users report this mod actually reduces fps so make sure you test what effect it has on your computer:
https://steamcommunity.com/sharedfiles/filedetails/?id=523824395
Turning off problem notifications might help with weak graphics cards or older computers:
https://steamcommunity.com/sharedfiles/filedetails/?id=917543381
Exiting the game
Updated: March 2020
You can even speed up exiting the game to desktop with a mod!
https://steamcommunity.com/sharedfiles/filedetails/?id=2037888659
Hardware Performance
Updated: January 2020
Performance tuned hardware is worth the effort

Benchmarking
Windows users can use the free User Benchmark[www.userbenchmark.com] app to benchmark hadware components. It runs speed tests on each of your hardware components (CPU, RAM, Disk, Graphics, etc) and then compares them to results from thousands of other users around the world.

If any of your components are running slowly, compared to other users with the same component, it will tell you and then you can investigate why. Often you might need to update drivers (always get latest drivers from manufacturer website) or possibly tweak settings in your BIOS. For example, my memory was performing really slow (I forgot to set its speed in BIOS after replacing motherboard):


Cooling
If your CPU or GPU overheat they will throttle down to a much slower clock speed, and everything will grind.

To prevent throttling, limit the frame rate (yes, I know, crazy, right?) with the "-limitfps" launch option.

Make sure your fans, fins and air filters aren't clogged with dust! I've had to vacuum dust out of my rig several times already to keep the cooling working at full capacity.

Liquid cooling is often the most effective, if you can afford it, but the liquid can corrode the cooler and clog it up. Do your research before investing time and money in liquid cooling!

Overclocking
Overclocking forces your hardware to run faster than it normally would, but there are risks involved: It can physically destroy your CPU, RAM and GPU.

Modern gaming motherboards often include automatic overclocking features that will do most of the scary stuff for you, but often you'll still need to read the internets and do some manual tweaking for god-tier results.

Overclocking the CPU will get much better results than overclocking the GPU.

Always speak to the internet before overclocking and make sure you have proper cooling in your rig. There's no point overclocking if that overheats your rig and causes throttling = it will be even slower than before you overclocked!

Getting Help
If you need help with hardware, a good place to start is r/pcmasterrace on Reddit.
Asset Creators only...
Updated: September 2019
If you aren't an asset creator, skip this section.

Model Size
Here's what CO had to say on asset creation:

Originally posted by CO_Dae:
The model size is not limited other than by Unity's limit of about 65000 vertices per mesh, but even approaching that is too much for single assets. To give some rough guidelines, the triangle count of the building models in the stock game ranges from less than 1000 triangles for the smallest and simplest buildings to about 5000 for large and complex buildings. A few exceptional buildings use up to 10-15k triangles. Vehicles typically have 500-1000 triangles, while trees vary from a few hundred for simple bushes to about 2000 for the more complex ones. Also note that a large number of props can also make the asset rendering slower, which is why there is a limit in the asset editor.

Please post details of your asset stats (triangles, texture sizes, etc) on your workshop pages so users don't need to guess what impact your asset will have on their game. Taking a screen shot of your asset stats shown by Mesh Info mod is a quick way to achieve that.

Texture, Material and Mesh sharing
Please read LSM Guide for Asset Authors to learn how to optimise your assets for Loading Screen Mod. This makes a huge difference for end users, as it can save them huge amounts of RAM and greatly speed up game loading if the assets they use are optimised for resource sharing.

Also, please read the small guides at bottom of that LSM Guide. If your asset is throwing errors, users are likely to downvote it and unsubscribe it.

CSL Modding site
If you haven't already found it, head over to https://cslmodding.info which contains loads of excellent information and guides on asset creation.
Mod Developers only...
Updated: December 2019
If you aren't developing mods, skip this section.

Make sure you're not using a debug version[github.com] of mono dll.

And check you don't have any DEBUG builds of mods installed. In particular, per-frame log file spamming can decimate frame rate.

The games' UI component system is slow, so please try and minimise the number of UI components you use. In particular, avoid anything that udpdates per frame (eg. `Update()` method).

If you want to speed up testing of your mod in-game, here are some suggestions:
  • In LSM, disable "Load enabled assets" option, but keep the "Load used assets". This will greatly reduce loading time.
  • See "Launching the App" section above to reduce app launch time.
  • Bugfixing saves from users? See Tips for working with savegames[github.com].
Got any other tips?
If you can think of other useful things to add to this guide, or have any comments, let me know in the comments below.

If you found the guide useful, please consider supporting me on ko-fi[ko-fi.com].
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118 Comments
Enter Plasma Sep 13 @ 7:26am 
Thanks for the great guide!
I've written my own performance guide that builds on top of yours, and is mostly for hardware and more advanced performance tuning.
Check it out here: https://steamcommunity.com/sharedfiles/filedetails/?id=2227833834
tobyborrett Sep 4 @ 5:45am 
FPS can be shown on all OS's with Monitor It! You can also get RAM and swapfile usage. ;)
tobyborrett Sep 4 @ 5:35am 
Hey, great guide, enjoyed reading it but was using all the tips already. As a Linux daily driver, here's some answers to your questions:
GPU drivers are included with the OS on most mainstream distros, C:S doesn't need professional drivers so nothing needs to be done here.
To display FPS, I just use steams tool, it works exactly the same or it can be enabled via command line. Also, some monitors have a built in feature to do this.
My version of Linux doesn't have a high performance mode as far as I know.
Hope this helps, and thanks again for the great guide
Fran-cys Aug 27 @ 11:16pm 
My Specs are Lenovo L340

intel i5-9300H
4 + 8gb ram
Nvidia gtx 1650

How do i run?
emma1293 Jul 24 @ 5:11am 
all week this game has been crashing for me i have done everything from uninstalling the game to checking drivers there's nothing wrong with my computer drivers... i have a report to send to developer but i have no idea had to send to developer!... i've asked in another thread but people were just rude! this game worked fine for ages even if i didn't have a 16gb like it's been said loads of times!
CaddyShack Jun 20 @ 7:30pm 
My game has started freezing right as it opens the save while playing on my brand-new highly optimized for gaming laptop :steamsad:

I've had to go back to this very handy and useful guide to diagnose what I can do to help it not freeze up.
vilamno Jun 3 @ 7:26pm 
If I have enough disk space for pagefile(1TB), will there be upper limit for it?
NOiZE Jun 1 @ 11:33pm 
Disabling Vehicle prop generation in the settings of the "Tree and Vehicle Props" mod reduced my loadtime by 6 minutens! (from 14 to 8 minutes)

unsubscribing from Prop it Up reduced it by another 3 minutes!
NOiZE May 31 @ 7:37am 
Just wanted to share that I just removed MOM and I only got back 20 seconds in reduced loading time.
aubergine18  [author] May 26 @ 10:18am 
You might get some increase with more RAM, but the main issue with this game is how it utilises the CPU. I'll post here when new FPS Booster mod is released (hopefully soon).