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The mod build package is an open-source NuGet package which automates the MSBuild configuration for SMAPI mods and related tools. The package is fully compatible with Linux, macOS, and Windows.



  1. Create an empty library project.
  2. Reference the Pathoschild.Stardew.ModBuildConfig NuGet package.
  3. Write your code.
  4. Compile on any platform.
  5. Run the game to play with your mod.


The package includes several features to simplify mod development (see configure to change how these work):

  • Detect game path:
    The package automatically finds your game folder by scanning the default install paths and Windows registry. It adds two MSBuild properties for use in your .csproj file if needed: $(GamePath) and $(GameExecutableName).

  • Add assembly references:
    The package adds assembly references to SMAPI, Stardew Valley, xTile, and the game framework (MonoGame on Linux/macOS, XNA Framework on Windows). It automatically adjusts depending on which OS you're compiling it on. If you use Harmony, it can optionally add a reference to that too.

  • Copy files into the Mods folder:
    The package automatically copies your mod's DLL and PDB files, manifest.json, i18n files (if any), the assets folder (if any), and build output into your game's Mods folder when you rebuild the code, with a subfolder matching the mod's project name. That lets you try the mod in-game right after building it.

  • Create release zip:
    The package adds a zip file in your project's bin folder when you rebuild the code, in the format recommended for uploading to mod sites like Nexus Mods. This includes the same files as the previous feature.

  • Launch or debug mod:
    On Windows only, the package configures Visual Studio so you can launch the game and attach a debugger using Debug > Start Debugging or Debug > Start Without Debugging. This lets you set breakpoints in your code while the game is running, or make simple changes to the mod code without needing to restart the game. This is disabled on Linux/macOS due to limitations with the Mono wrapper.

  • Preconfigure common settings:
    The package automatically enables .pdb files (so error logs show line numbers to simplify debugging), and enables support for the simplified SDK-style .csproj format.

  • Add code warnings:
    The package runs code analysis on your mod and raises warnings for some common errors or pitfalls. See code warnings for more info.


How to set options

You can configure the package by setting build properties, which are essentially tags like this:


There are two places you can put them:

  • Global properties apply to every mod project you open on your computer. That's recommended for properties you want to set for all mods (e.g. a custom game path). Here's where to put them:

    1. Open the home folder on your computer (see instructions for Linux, macOS, or Windows).
    2. Create a stardewvalley.targets file with this content:
    3. Add the properties between the <PropertyGroup> and </PropertyGroup>.
  • Project properties apply to a specific project. This is mainly useful for mod-specific options like the mod name. Here's where to put them:

    1. Open the folder containing your mod's source code.
    2. Open the .csproj file in a text editor (Notepad is fine).
    3. Add the properties between the first <PropertyGroup> and </PropertyGroup> tags you find.

Available properties

These are the options you can set:

  • Game properties:
    property effect

    The absolute path to the Stardew Valley folder. This is auto-detected, so you usually don't need to change it.


    The absolute path to the folder containing the game's installed mods (defaults to $(GamePath)/Mods), used when deploying the mod files.


    The filename for the game's executable (i.e. StardewValley.exe on Linux/macOS or Stardew Valley.exe on Windows). This is auto-detected, and you should almost never change this.


    The game framework for which the mod is being compiled (one of Xna or MonoGame). This is auto-detected based on the platform, and you should almost never change this.

  • Mod build properties:
    property effect

    Whether to add a reference to Harmony (default false). This is only needed if you use Harmony.


    Whether to copy the mod files into your game's Mods folder (default true).


    Whether to create a release-ready .zip file in the mod project's bin folder (default true).


    The mod name for its folder under Mods and its release zip (defaults to the project name).


    The folder path where the release zip is created (defaults to the project's bin folder).

  • Specialized properties:
    property effect

    Whether to copy game and framework DLLs into the mod folder (default false). This is useful for unit test projects, but not needed for mods that'll be run through SMAPI.


    Whether to configure the project so you can launch or debug the game through the Debug menu in Visual Studio (default true). There's usually no reason to change this, unless it's a unit test project.


    A comma-delimited list of regex patterns matching files to ignore when deploying or zipping the mod files (default empty). For crossplatform compatibility, you should replace path delimiters with [/\\].

    For example, this excludes all .txt and .pdf files, as well as the assets/paths.png file:

    <IgnoreModFilePatterns>\.txt$, \.pdf$, assets[/\\]paths.png</IgnoreModFilePatterns>

Code warnings


The NuGet package adds code warnings in Visual Studio specific to Stardew Valley. For example:

You can hide the warnings if needed using the warning ID (shown under 'code' in the Error List).

See below for help with specific warnings.

Avoid implicit net field cast

Warning text:

This implicitly converts '{{expression}}' from {{net type}} to {{other type}}, but {{net type}} has unintuitive implicit conversion rules. Consider comparing against the actual value instead to avoid bugs.

Stardew Valley uses net types (like NetBool and NetInt) to handle multiplayer sync. These types can implicitly convert to their equivalent normal values (like bool x = new NetBool()), but their conversion rules are unintuitive and error-prone. For example, item?.category == null && item?.category != null can both be true at once, and building.indoors != null can be true for a null value.

Suggested fix:

  • Some net fields have an equivalent non-net property like monster.Health (int) instead of (NetInt). The package will add a separate AvoidNetField warning for these. Use the suggested property instead.
  • For a reference type (i.e. one that can contain null), you can use the .Value property:
    if (building.indoors.Value == null)
    Or convert the value before comparison:
    GameLocation indoors = building.indoors;
    if(indoors == null)
       // ...
  • For a value type (i.e. one that can't contain null), check if the object is null (if applicable) and compare with .Value:
    if (item != null && item.category.Value == 0)

Avoid net field

Warning text:

'{{expression}}' is a {{net type}} field; consider using the {{property name}} property instead.

Your code accesses a net field, which has some unusual behavior (see AvoidImplicitNetFieldCast). This field has an equivalent non-net property that avoids those issues.

Suggested fix: access the suggested property name instead.

Avoid obsolete field

Warning text:

The '{{old field}}' field is obsolete and should be replaced with '{{new field}}'.

Your code accesses a field which is obsolete or no longer works. Use the suggested field instead.

Wrong processor architecture

Warning text:

The target platform should be set to 'Any CPU' for compatibility with both 32-bit and 64-bit versions of Stardew Valley (currently set to '{{current platform}}').

Mods can be used in either 32-bit or 64-bit mode. Your project's target platform isn't set to the default 'Any CPU', so it won't work in both. You can fix it by setting the target platform to 'Any CPU'.


How do I set the game path?

The package detects where your game is installed automatically, so you usually don't need to set it manually. If it can't find your game or you have multiple installs, you can specify the path yourself.

To do that:

  1. Get the full folder path containing the Stardew Valley executable.
  2. See configure to add this property:
  3. Replace PATH_HERE with your game's folder path (don't add quotes).

The configuration will check your custom path first, then fall back to the default paths (so it'll still compile on a different computer).

How do I change which files are included in the mod deploy/zip?

For custom files, you can add/remove them in the build output. (If your project references another mod, make sure the reference is not marked 'copy local'.)

To exclude a file the package copies by default, see IgnoreModFilePatterns under configure.

Can I use the package for non-mod projects?

You can use the package in non-mod projects too (e.g. unit tests or framework DLLs). Just disable the mod-related package features (see configure):


If you need to copy the referenced DLLs into your build output, add this too:


For SMAPI developers

The mod build package consists of three projects:

project purpose
StardewModdingAPI.ModBuildConfig Configures the build (references, deploying the mod files, setting up debugging, etc).
StardewModdingAPI.ModBuildConfig.Analyzer Adds C# analyzers which show code warnings in Visual Studio.
StardewModdingAPI.ModBuildConfig.Analyzer.Tests Unit tests for the C# analyzers.

The NuGet package is generated automatically in StardewModdingAPI.ModBuildConfig's bin folder when you compile it.

Release notes

Upcoming release

  • Improved analyzer performance by enabling parallel execution.


Released 30 March 2021.

  • Added a build warning when the mod isn't compiled for Any CPU.
  • Added a GameFramework build property set to MonoGame or Xna based on the platform. This can be overridden to change which framework it references.
  • Added support for building mods against the 64-bit Linux version of the game on Windows.
  • The package now suppresses the misleading 'processor architecture mismatch' warnings.


Released 23 September 2020.


Released 11 September 2020.

  • Added more detailed logging.
  • Fixed path's format is not supported error when using default Mods path in 3.2.


Released 07 September 2020.

  • Added option to change Mods folder path.
  • Rewrote documentation to make it easier to read.


Released 01 February 2020.

  • Added support for semantic versioning 2.0.
  • 0Harmony.dll is now ignored if the mod references Harmony directly (it's bundled with SMAPI).


Released 26 November 2019.

  • Updated for SMAPI 3.0 and Stardew Valley 1.4.
  • Added automatic support for assets folders.
  • Added $(GameExecutableName) MSBuild variable.
  • Added support for projects using the simplified .csproj format.
  • Added option to disable game debugging config.
  • Added .pdb files to builds by default (to enable line numbers in error stack traces).
  • Added optional Harmony reference.
  • Fixed Newtonsoft.Json.pdb included in release zips when Json.NET is referenced directly.
  • Fixed <IgnoreModFilePatterns> not working for i18n files.
  • Dropped support for older versions of SMAPI and Visual Studio.
  • Migrated package icon to NuGet's new format.


Released 28 October 2018.

  • Added support for SMAPI 2.8+ (still compatible with earlier versions).
  • Added default game paths for 32-bit Windows.
  • Fixed valid manifests marked invalid in some cases.


Released 27 July 2018.

  • Added support for Stardew Valley 1.3.
  • Added support for non-mod projects.
  • Added C# analyzers to warn about implicit conversions of Netcode fields in Stardew Valley 1.3.
  • Added option to ignore files by regex pattern.
  • Added reference to new SMAPI DLL.
  • Fixed some game paths not detected by NuGet package.


Released 01 November 2017.

  • Fixed compatibility issue on Linux.


Released 11 October 2017.

  • Fixed mod deploy failing to create subfolders if they don't already exist.


Released 11 October 2017.

  • Added: mods are now copied into the Mods folder automatically (configurable).
  • Added: release zips are now created automatically in your build output folder (configurable).
  • Added: mod deploy and release zips now exclude Json.NET automatically, since it's provided by SMAPI.
  • Added mod's version to release zip filename.
  • Improved errors to simplify troubleshooting.
  • Fixed release zip not having a mod folder.
  • Fixed release zip failing if mod name contains characters that aren't valid in a filename.


Released 28 July 2017.

  • Fixed issue where i18n folders were flattened.
  • The manifest/i18n files in the project now take precedence over those in the build output if both are present.


Released 28 July 2017.

  • Added option to create release zips on build.
  • Added reference to XNA's XACT library for audio-related mods.


Released 10 July 2017.

  • Further improved crossplatform game path detection.
  • Removed undocumented GamePlatform build property.


Released 09 July 2017.

  • Improved crossplatform game path detection.


Released 05 June 2017.

  • Added support for deploying mod files into Mods automatically.
  • Added a build error if a game folder is found, but doesn't contain Stardew Valley or SMAPI.


Released 23 January 2017.

  • Added support for setting a custom game path globally.
  • Added default GOG path on macOS.


Released 11 January 2017.

  • Fixed detection of non-default game paths on 32-bit Windows.
  • Removed support for SilVerPLuM (discontinued).
  • Removed support for overriding the target platform (no longer needed since SMAPI crossplatforms mods automatically).


Released 31 December 2016.

  • Added support for non-default game paths on Windows.


Released 24 October 2016.

  • Exclude game binaries from mod build output.


Released 21 October 2016.

  • Added support for overriding the target platform.


Released 21 October 2016.

  • Initial release.
  • Added support for detecting the game path automatically.
  • Added support for injecting XNA/MonoGame references automatically based on the OS.
  • Added support for mod builders like SilVerPLuM.