Publish a Kotlin/Native library as NuGet

Configure a Kotlin Multiplatform module, package its native binaries and generated C# API, then add the resulting MyCatLib package to a .NET project.

1. Apply the plugin and build shared libraries

Apply Kotlin Multiplatform and the NuGet plugin, then give every supported native target the same shared-library baseName:

plugins {
  kotlin("multiplatform")
  id("io.github.xxfast.kotlin.native.nuget") version "<version>"
}

kotlin {
  mingwX64 {
    binaries {
      sharedLib {
        baseName = "mycatlib"
      }
    }
  }

  macosArm64 {
    binaries {
      sharedLib {
        baseName = "mycatlib"
      }
    }
  }
}

Replace <version> with the version shown in Getting started, and keep it pinned. Only configured targets in the supported target table are added to the package.

2. Configure the NuGet package

Publish every public declaration below rootPackage into the corresponding C# namespace:

nuget {
  publish {
    packageId = "MyCatLib"
    version = "1.0.0"
    authors = "yourname"
    description = "A Kotlin/Native library for cat lovers"
    rootPackage = "com.example.cats"
  }
}

For example, add this API under src/nativeMain/kotlin/com/example/cats/Cat.kt:

package com.example.cats

interface Pet {
  val name: String
  fun speak(): String
}

enum class Mood { HAPPY, SLEEPY, GRUMPY }

abstract class Animal(override val name: String) : Pet

class Cat(
  name: String,
  val lives: Int = 9,
) : Animal(name) {
  var brother: Cat? = null
  var mood: Mood = Mood.SLEEPY
  val toys: List<Toy> = listOf(Toy("Mouse", "Gray"))
  val onMeow: () -> String = { "Meow! My name is $name" }

  override fun speak(): String = "Meow!"
}

data class Toy(val name: String, val color: String)

class Box<T>(val item: T)

fun owner(name: String): String? = if (name == "Oreo") "Isuru" else null

The root package maps to the MyCatLib C# namespace. After adding the NuGet package to a .NET project, use the generated API like this:

using MyCatLib;

using var oreo = new Cat("Oreo", 9);
Console.WriteLine(oreo.Name);    // Oreo
Console.WriteLine(oreo.Speak()); // Meow!

using var mylo = new Cat("Mylo", 9);
oreo.Brother = mylo;
oreo.Mood = Mood.Happy;

See Publishing Kotlin to C# for the supported Kotlin constructs and their generated C# shapes. The complete package metadata options are in the nuget {} DSL reference.

3. Build and consume the package

Build the package from the project root:

./gradlew packNuget

The package is written to build/nuget/MyCatLib.1.0.0.nupkg. See Gradle tasks for the complete output layout.

Add that directory as a NuGet package source, then add a PackageReference from the C# consumer. For example, create a NuGet.Config beside the .NET solution:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
    <add key="mycatlib-local" value="../my-cat-lib/build/nuget" />
  </packageSources>
</configuration>

<ItemGroup>
  <PackageReference Include="MyCatLib" Version="1.0.0" />
</ItemGroup>

Adjust the relative feed path for your directory layout. Keep the package reference version in sync with publish {}. NuGet brings in the generated C# source and selects the native binary for the consumer's runtime identifier.

A framework-dependent C# build also needs a runtime identifier so MSBuild copies the matching native asset beside the host. For a cross-platform project, use the SDK host RID:

<RuntimeIdentifier>$(NETCoreSdkRuntimeIdentifier)</RuntimeIdentifier>
<SelfContained>false</SelfContained>

Do not hardcode one host RID into a cross-platform test project. For deployment, select the RID of the target environment.

4. Publish the package to a feed

The local package source above is useful while developing and testing the library. To distribute MyCatLib, publish the generated package to NuGet.org or a private NuGet feed instead.

packNuget creates the .nupkg, but does not upload it. With the .NET SDK installed and credentials for the destination feed, push the package with dotnet nuget push:

dotnet nuget push build/nuget/MyCatLib.1.0.0.nupkg \
  --source https://api.nuget.org/v3/index.json \
  --api-key <NUGET_API_KEY>

For a private feed, replace --source with that feed's endpoint and use credentials accepted by the feed. Consumers then reference MyCatLib with the same normal PackageReference shown above and restore it from the published feed. They do not need the mycatlib-local entry in their NuGet.Config.

Last modified: 21 July 2026