KMP

Learn the Kotlin Multiplatform (KMP) concept.

What is KMP?

Kotlin Multiplatform (KMP) lets you share the same Kotlin code across several platforms. It supports JVM, Android, iOS, JS and Native targets.

A KMP project starts with the kotlin("multiplatform") plugin in Gradle. Shared code goes into the commonMain source set; platform-specific code goes into each target's own source set. In this lesson we model the concept with a simple kmpInfo function.

KMP targets

KMP hosts many targets in the same project: JVM, Android, iOS (arm64, x64), JS and Native (Linux, Windows, macOS).

Each target is added with a separate Gradle block; for example jvm(), iosArm64(), js(). Targets have their own source sets: jvmMain, iosMain, jsMain. Shared code lives in commonMain and every target can use it. Platform-specific parts go into the matching target source set.

Exercise Write kmpInfo

Define fun kmpInfo(): String. It should return "KMP". In main, write println(kmpInfo()).

Show example solution

fun kmpInfo(): String = "KMP"
fun main() {
    println(kmpInfo())
}

Test yourself

Which Gradle plugin starts a KMP project?
- application
- kotlin("jvm")
- kotlin("multiplatform")
- java-library
Show answer

kotlin("multiplatform") — The kotlin("multiplatform") plugin starts a KMP project.

Complete the plugin line

plugins { kotlin("____") }

Show answer

plugins { kotlin("multiplatform") }

Match the KMP parts

kotlin("multiplatform")

Gradle plugin
commonMain

Shared code
iosArm64()

iPhone target
js()

Browser target

Next lesson: commonMain

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