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Mod Manager for SimCity 4 plugins.

This program handles the process of downloading and installing SimCity 4 plugins, including all their dependencies.

It helps you assemble a full Plugins folder very quickly, and also keeps your plugins up-to-date and organized.

Usage

  • Download: Choose between

    • the desktop application for Windows 10+,
    • the desktop application for Linux, and
    • the cross-platform web-app for other platforms.
  • Verify the checksum of the downloaded ZIP file against the checksums published on Github (optional).

  • Extract the contents of the downloaded ZIP file to any location of your choice.

  • At first launch of the application, it guides you through the initial setup: creating a new Profile and configuring the location of your Plugins folder.

  • Go to Find Packages to search and select packages to install (for example cyclone-boom:save-warning). There are already more than 5000 plugins with compatible metadata to choose from. Once satisfied, go to the Dashboard and hit Update to download and install the plugin files. Files are downloaded directly from Simtropolis or other sites like SC4Evermore, ToutSimCities, SimCityKurier (archived), Hide and Seek! (archived) and GitHub.

  • If you are signed in to Simtropolis, watch out for the “Install with sc4pac” button on the STEX. It appears for plugins that can be installed with sc4pac. Start small and gradually build up your Plugins folder. Don't download everything at once.

    image.png

  • Install null-45:startup-performance-optimization-dll if you use the Windows digital edition of the game. (This adds support for plugin file paths exceeding the 260 character limit on Windows, which could otherwise be a problem for a small number of packages that use deeply-nested, long file names.)

  • Install memo:lua-sandbox-dll if you use the Windows digital edition of the game. (This provides a more secure environment for your plugins by preventing mods from using unsafe Lua functions.)

  • Be aware that Simtropolis has a download limit of 20 files per day for guests. To avoid this limit, go to Settings and set up your personal authentication token for Simtropolis (step-by-step guide). Alternatively, simply continue the installation process the next day.

Plugins folder structure

050-load-first
060-config
075-my-plugins         (your existing manually installed plugins)
100-props-textures
110-resources
140-ordinances
150-mods
170-terrain
180-flora
200-residential
300-commercial
360-landmark
400-industrial
500-utilities
600-civics
610-safety
620-education
630-health
640-government
650-religion
660-parks
700-transit
710-automata
770-network-addon-mod
895-my-overrides       (your manually installed zzz-folders)
900-overrides

Packages are installed into subfolders prefixed by an even number, as the order in which files are loaded by the game is important. This ensures a consistent load order. Files you install manually should be put into subfolders prefixed by an odd number (ideally before 900-overrides).

Migrating an existing Plugins folder

If you already have a non-empty Plugins folder and want to switch to sc4pac, start by moving the bulk of your manually installed files into a new subfolder 075-my-plugins and your zzz-folders into 895-my-overrides to ensure correct load order. Once you install more and more packages and dependencies with sc4pac, delete the corresponding older, redundant, manually installed files to avoid duplication or version conflicts. If a dependency was installed with sc4pac, there is no need to keep older manually installed copies of it.

In the long run, create additional odd-numbered subfolders for better organization of your manually installed files and to fine-tune load order.

Managing multiple Plugins folders

The sc4pac GUI supports creating multiple Profiles. For example, you could use a unique Profile for each of your Regions. Each Profile corresponds to a Plugins folder.

Important: Make sure to select distinct locations for all your Plugins folders to avoid interference between Profiles.

You can use the SC4 launch parameter -UserDir:"..." to start the game with a custom location for the game's user directory, which contains the Plugins folder (and Regions folder).

Uninstalling

  • Uninstall all packages for each Profile (see Dashboard  Profile  Delete options).
  • Delete the download cache folder (see Dashboard).
  • Remove the profiles configuration folder (see Settings).
  • Finally, delete the folder containing the sc4pac program files.

Documentation

Visit the Troubleshooting & FAQ section of the sc4pac Website for more information, or the development & support thread.

To make your own uploads installable with sc4pac, see the topic about the sc4pac STEX integration.

Credits

A big thank you for contributions to sc4pac@smf_16 @nos.17 @Zasco @Flann @Shadow Assassin @Cyclone Boom @CorinaMarie @Null 45 @Ulisse Wolf @timdmackey.


What's New 1.6.1   View Changelog


Released

Changes since version 1.6.0

  • updated external documentation files (no need to redownload)

Upgrading from previous versions:

Simply extract the ZIP file. You can remove the previous application files in favor of the newly extracted files.

  • Like 45
  • Yes 2
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User Feedback



Recommended Comments

@Dono I've added this point to the FAQ: Creating a back-up.

 

On 10/9/2025 at 12:31 AM, outdatedSIM said:

During installation of sc4pac I read to choose a separate folder for each profile, so I did not take \My Documents\SimCity 4\Plugins, instead I took \My Documents\SimCity 4\Plugins\MAIN - is this correct?

For anyone coming across this – no, usually it's best to name the folder "Plugins". See the detailed example in the FAQ.

  • Like 2

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I have installed the most updated version of Java and it's still telling me that my Java isn't the most up to date and won't run.

Screenshot 2025-11-06 140948.png

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Received this today when trying to download a mod. Any help would be appreciated.

 

```
Sc4pac GUI version: 1.4.0
Sc4pac CLI version: 0.9.0
Platform: windows
Web: false
Java: 25 - OpenJDK 64-Bit Server VM 25.0.1+8-LTS/25.0.1, Eclipse Adoptium, OpenJDK Runtime Environment, C:\Program Files\Eclipse Adoptium\jdk-25.0.1.8-hotspot
OS (Java): Windows 11 10.0 amd64
OS (Dart): windows - "Windows 10 Home" 10.0 (Build 26200)
Dart: 3.5.3 (stable) (Wed Sep 11 16:22:47 2024 +0000) on "windows_x64"
Exe: C:\Users\james\Desktop\sc4pac-gui-windows-x64 (2)\sc4pac-gui.exe
Arguments: [sc4pac:///package?pkg=simfox%3Acandy-garden&channel=https%3A%2F%2Fsc4pac.simtropolis.com%2F]

Error type: /error/extraction-failed
Error title: Failed to extract C:\Users\james\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\16861-simfox-candygarden\%3Fdo%3Ddownload%26r%3D39785.
Error detail: Error on ZipFile C:\Users\james\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\16861-simfox-candygarden\%3Fdo%3Ddownload%26r%3D39785

Redownloading the package might resolve the problem in case of issues with the downloaded file:
- Package: simfox:candy-garden
- Asset ID: simfox-candygarden
- Downloaded and cached file: C:\Users\james\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\16861-simfox-candygarden\%3Fdo%3Ddownload%26r%3D39785

Init phase: InitPhase.initialized
Authority: localhost:51515
Authenticated: false
Profiles config folder: C:\Users\james\AppData\Roaming\io.github.memo33\sc4pac\config\profiles
Profile ID: 1
Profile name: Timbuktu
Plugins folder: C:\Users\james\Documents\SimCity 4\Plugins
Cache folder: C:\Users\james\AppData\Local\io.github.memo33\sc4pac\cache

Server log:
WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by scala.runtime.LazyVals$ (file:/C:/Users/james/Desktop/sc4pac-gui-windows-x64%20(2)/cli/sc4pac-cli.jar)
WARNING: Please consider reporting this to the maintainers of class scala.runtime.LazyVals$
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
WARNING: A restricted method in 
java.lang.System has been called
WARNING: java.lang.System::load has been called by org.fusesource.jansi.internal.JansiLoader in an unnamed module (file:/C:/Users/james/Desktop/sc4pac-gui-windows-x64%20(2)/cli/sc4pac-cli.jar)

WARNING: Use --enable-native-access=
ALL-UNNAMED to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled
```

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I have a problem with using version 1.4.0

 

```
Sc4pac GUI version: 1.4.0
Sc4pac CLI version: 0.9.0
Platform: windows
Web: false
Java: 25 - Java HotSpot(TM) 64-Bit Server VM 25.0.1+8-LTS-27/25.0.1, Oracle Corporation, Java(TM) SE Runtime Environment, C:\Program Files\Java\jdk-25
OS (Java): Windows 11 10.0 amd64
OS (Dart): windows - "Windows 10 Home" 10.0 (Build 26200)
Dart: 3.5.3 (stable) (Wed Sep 11 16:22:47 2024 +0000) on "windows_x64"
Exe: C:\Users\Admin\Desktop\sc4pac 1.4.0\sc4pac-gui.exe
Arguments: []

Error type: /error/extraction-failed
Error title: Failed to extract C:\Users\Admin\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\22400-maxis-prop-names-and-query-fix\%3Fdo%3Ddownload.
Error detail: Error on ZipFile C:\Users\Admin\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\22400-maxis-prop-names-and-query-fix\%3Fdo%3Ddownload

Redownloading the package might resolve the problem in case of issues with the downloaded file:
- Package: t-wrecks:maxis-prop-names-and-query-fix
- Asset ID: t-wrecks-maxis-prop-names-and-query-fix
- Downloaded and cached file: C:\Users\Admin\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\22400-maxis-prop-names-and-query-fix\%3Fdo%3Ddownload

Init phase: InitPhase.initialized
Authority: localhost:51515
Authenticated: false
Profiles config folder: C:\Users\Admin\AppData\Roaming\io.github.memo33\sc4pac\config\profiles
Profile ID: 1
Profile name: GAMER
Plugins folder: C:\Users\Admin\Documents\SimCity 4\Plugins
Cache folder: C:\Users\Admin\AppData\Local\io.github.memo33\sc4pac\cache

Server log:
WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by scala.runtime.LazyVals$ (file:/C:/Users/Admin/Desktop/sc4pac%201.4.0/cli/sc4pac-cli.jar)
WARNING: Please consider reporting this to the maintainers of class scala.runtime.LazyVals$
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
WARNING: A restricted method in 
java.lang.System has been called
WARNING: java.lang.System::load has been called by org.fusesource.jansi.internal.JansiLoader
 in an unnamed module (file:/C:/Users/Admin/Desktop/sc4pac%201.4.0/cli/sc4pac-cli.jar)
WARNING: Use --enable-native-access=
ALL-UNNAMED to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled
```

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The same problem. Java is updated.

```
Sc4pac GUI version: 1.4.0
Sc4pac CLI version: null
Platform: windows
Web: false
Java: null
OS (Java): null
OS (Dart): windows - "Windows 10 Home Single Language" 10.0 (Build 19045)
Dart: 3.5.3 (stable) (Wed Sep 11 16:22:47 2024 +0000) on "windows_x64"
Exe: D:\Application\SimCity 4 Tools\SC4Pac\sc4pac-gui.exe
Arguments: []

Error type: /error/unexpected
Error title: The Java version installed on your system is too old. Install a more recent version of Java.
Error detail: java.lang.UnsupportedClassVersionError: io/github/memo33/sc4pac/cli/CliMain has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

Init phase: InitPhase.connecting
Authority: localhost:51515
Authenticated: null
Profiles config folder: null
Profile ID: null
Profile name: null
Plugins folder: null
Cache folder: null

Server log:
Exception 
in thread "main" 
java.lang.UnsupportedClassVersionError: io/github/memo33/sc4pac/cli/CliMain has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)

    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)

    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
```

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9 minutes ago, memo said:

@Burinis The Java version installed on your system is too old. Install a more recent version of Java.

No. I have Version 8 Update 471. But it still doesn't work.

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1 hour ago, Burinis said:

No. I have Version 8 Update 471. But it still doesn't work.

What a nice security breach you have

Java 8 is obsolete, and Oracle no longer provides the latest versions of Java to the public. Uninstall Java 8, restart your computer, and install the latest version of Java available here (the latest version is Java 25).

https://adoptium.net/temurin/releases

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1 hour ago, Ulisse Wolf said:

What a nice security breach you have

Java 8 is obsolete, and Oracle no longer provides the latest versions of Java to the public. Uninstall Java 8, restart your computer, and install the latest version of Java available here (the latest version is Java 25).

https://adoptium.net/temurin/releases

THANKS!!! IT HELPED!!!

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Hi.

I like the mod manager very much.

I have a question. Is it possible to uninstall a specific mod, because I do not see any option for this ?

Best Regards.

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Hi, thank you for creating this awesome tool. Im having trouble using it tho. I got around the inital extraction error that was caused by Simtropolis token, but now I have a new issue. Log down below. 

```
Sc4pac GUI version: 1.4.0
Sc4pac CLI version: 0.9.0
Platform: windows
Web: false
Java: 25 - OpenJDK 64-Bit Server VM 25.0.1+8-LTS/25.0.1, Eclipse Adoptium, OpenJDK Runtime Environment, C:\Program Files\Eclipse Adoptium\jdk-25.0.1.8-hotspot
OS (Java): Windows 11 10.0 amd64
OS (Dart): windows - "Windows 10 Pro" 10.0 (Build 26100)
Dart: 3.5.3 (stable) (Wed Sep 11 16:22:47 2024 +0000) on "windows_x64"
Exe: D:\Games\SimCity4\ModManager\sc4pac-gui.exe
Arguments: []

Error type: /error/extraction-failed
Error title: Failed to extract C:\Users\mihke\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\36841-i-r-fix\%3Fdo%3Ddownload.
Error detail: Error on ZipFile C:\Users\mihke\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\36841-i-r-fix\%3Fdo%3Ddownload

Redownloading the package might resolve the problem in case of issues with the downloaded file:
- Package: memo:i-r-fix
- Asset ID: memo-i-r-fix
- Downloaded and cached file: C:\Users\mihke\AppData\Local\io.github.memo33\sc4pac\cache\coursier\https\community.simtropolis.com\files\file\36841-i-r-fix\%3Fdo%3Ddownload

Init phase: InitPhase.initialized
Authority: localhost:51515
Authenticated: true
Profiles config folder: C:\Users\mihke\AppData\Roaming\io.github.memo33\sc4pac\config\profiles
Profile ID: 1
Profile name: Mike
Plugins folder: C:\Users\mihke\Documents\SimCity 4\Plugins
Cache folder: C:\Users\mihke\AppData\Local\io.github.memo33\sc4pac\cache

Server log:
WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by scala.runtime.LazyVals$ (file:/D:/Games/SimCity4/ModManager/cli/sc4pac-cli.jar)
WARNING: Please consider reporting this to the maintainers of class scala.runtime.LazyVals$
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
WARNING: A restricted method in 
java.lang.System has been called
WARNING: java.lang.System::load has been called by 
org.fusesource.jansi.internal.JansiLoader in an unnamed module (file:/D:/Games/SimCity4/ModManager/cli/sc4pac-cli.jar)

WARNING: Use --enable-native-access=
ALL-UNNAMED
 to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled
```

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@mihkelyo Once you've set up the token, redownload the affected package (as suggested in the error message) using "Redownload & Reinstall", or empty the entire Cache folder if multiple packages are affected.

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unfortunately this changed nothing. Running into the same error.
 Edit: nevermind, actually deleting the cache folder fixed it. Tyvm!

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To anyone who still sees this error:

Quote

Error title: Failed to extract …

Error detail: Error on ZipFile

The issue has been fixed on the Simtropolis server side, today. Many thanks to @Cyclone Boom for making the changes. If you still see this error, use the "Redownload & Reinstall" button for the affected packages, or empty the Cache folder. Both approaches trigger a new download of the affected files.

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Mac users: For some reason on my mac the launch command included in the install that automatically opens a webpage doesn't work — doing it this way the website says 'authentication failed'. I have to manually run it from a terminal and paste the key into a web-browser to get it working. 

  • Like 1
  • Thanks 1

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Hi, I'm wanting to make an upcoming upload Sc4pac compatible, I have a submenu patch file I wanted to include in the upload. Do I need to have it as a separate download or is there a way to have it included? 

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On 12/21/2025 at 11:54 AM, Knives said:

Mac users: For some reason on my mac the launch command included in the install that automatically opens a webpage doesn't work — doing it this way the website says 'authentication failed'. I have to manually run it from a terminal and paste the key into a web-browser to get it working. 

Could you provide more color on how to run it in terminal and paste the key into a browser?  I've tried Safari, Chrome and Firefox and nothing seems to be working.  Here's what I see in Terminal and Safari.  Thanks!

Image 1-24-26 at 5.22 PM.png

Image 1-24-26 at 5.22 PM-1.png

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On 1/15/2026 at 8:32 PM, Dono said:

Hi, I'm wanting to make an upcoming upload Sc4pac compatible, I have a submenu patch file I wanted to include in the upload. Do I need to have it as a separate download or is there a way to have it included? 

@Dono There's no need for any special considerations. Sc4pac doesn't care at all what your mod does. Simply include the patch in the mod.

13 hours ago, mbgriffith1 said:

I've tried Safari, Chrome and Firefox and nothing seems to be working.  Here's what I see in Terminal and Safari.

@mbgriffith1 Fixed in version 1.4.3.

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A huge THANK YOU for making the Mod Manager work so well also under Linux. Works flawlessly in Fedora 42 KDE and has been a time and lifesaver. My first SimCity was on SNES in the 90's, but I'm actually new to the game and it's great to have this level of support when I got the itch to come back.

  • Like 1

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On 2/16/2025 at 1:21 AM, coxiesclub said:

I can not get this program to run on my newer computer. Keeps giving the error of not having the latest java. I have downloaded all there is to update. 

i have the same issue!

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