Compose Hot Reload

Build Compose UIs faster and let your creativity flow when designing multiplatform user interfaces.

With Compose Hot Reload, you can make UI code changes in a Compose Multiplatform app and see the results instantly, without needing to restart. The JetBrains Runtime intelligently reloads your code whenever it changes.

Important

Compose Hot Reload needs a JVM target in your multiplatform project. We're exploring adding support for other targets in the future.

Prerequisites

• Kotlin 2.1.20 or higher.
• Compose compiler 2.1.20 or higher.
• Compose Multiplatform 1.8.2
• JetBrains Runtime. To be compatible with JetBrains Runtime, your project needs to target Java 21 or earlier.

Set up your project

There are two ways to add Compose Hot Reload to your project:

• Create a project from scratch in IntelliJ IDEA or Android Studio
• Add it as a Gradle plugin to an existing project

Create a project from scratch

Follow the Kotlin Multiplatform quickstart guide to set up your environment and create a project. Be sure to select the desktop target when you create the project.

Apply the Gradle plugin to your project

1. In your project, update the version catalog. In gradle/libs.versions.toml, add the following code:

   composeHotReload = { id = "org.jetbrains.compose.hot-reload", version.ref = "composeHotReload"}
   

2. In the build.gradle.kts of your parent project, add the following code to your plugins {} block:

   plugins {
       alias(libs.plugins.composeHotReload) apply false
   }
   

   This prevents the Compose Hot Reload plugin from being loaded multiple times in each of your subprojects.

3. In the build.gradle.kts of the subproject containing your multiplatform application, add the following code to your plugins {} block:

   plugins { 
       alias(libs.plugins.composeHotReload)
   }
   

4. An installation of the JetBrains Runtime is required: Launching Compose Hot Reload with the Kotlin Multiplatform IDE plugin will re-use IntelliJ's installation of the JetBrains Runtime. If you want Gradle to automatically download the JetBrains Runtime, add the following code to your settings.gradle.kts file

   plugins {
       id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
   }
   

5. Click the Sync Gradle Changes button to synchronize Gradle files:

   

Use Compose Hot Reload

You can run your application with Compose Hot Reload from inside your IDE or from the CLI by using Gradle tasks.

From the IDE

In IntelliJ IDEA or Android Studio, in the gutter, click the Run icon of your main function:

• If you have the Kotlin Multiplatform IDE plugin installed, select Run 'MainKt [hotRunJvm]' with Compose Hot Reload (Beta).
• Otherwise, select Run 'MainKt [jvm]'.

From the CLI

Run tasks

The Compose Hot Reload plugin automatically creates the following tasks to launch the application in 'hot reload mode':

• :hotRunJvm: For multiplatform projects. The async alternative is :hotRunJvmAsync.
• :hotRun: For Kotlin/JVM projects. The async alternative :hotRunAsync.

You can run these Gradle tasks from the command line:

./gradlew :app:hotRunJvm

After making changes, save all files to automatically update your app's UI.

Custom target name

If you define a custom JVM target name, Gradle uses a different task name. For example, if your target name is desktop:

kotlin {
    jvm("desktop")
}

The task name is :hotRunDesktop.

Command-line arguments

Here's a list of all the possible arguments that you can use with the Gradle run tasks:

Argument	Description	Example
--mainClass <Main class FQN>	The main class to run.	./gradlew :app:hotRunJvm --mainClass com.example.MainKt
--autoReload --auto	Enable automatic reloading. Default: false.	./gradlew :app:hotRunJvm --autoReload ./gradlew :app:hotRunJvm --auto
--no-autoReload --no-auto	Disable automatic reloading.	./gradlew :myApp:hotRunJvm --no-auto ./gradlew :myApp:hotRunJvm --auto

Configure the main class

You can configure the main class directly in your build script instead of passing it as a command-line argument.

You can configure it in the Compose Hot Reload task:

tasks.withType<ComposeHotRun>().configureEach {
    mainClass.set("com.example.MainKt")
}

Or if you use Compose Multiplatform, in the application {} block:

compose.desktop {
    application {
        mainClass = "com.example.MainKt"
    }
}

Reload tasks

Warning

You can't run reload tasks with the --autoReload or --auto command-line argument.

The Compose Hot Reload plugin also provides Gradle tasks to recompile and reload your application:

• reload: Reload all, currently running, applications.
• hotReloadJvmMain: Reload all applications that use the jvmMain source set.

For example:

./gradlew :app:reload

Use developer builds

If you want to try the latest changes in Compose Hot Reload, you can use dev builds. To use the latest 'dev' builds of Compose Hot Reload, add the firework Maven repository in your settings.gradle.kts file:

pluginManagement {
    repositories {
        maven("https://packages.jetbrains.team/maven/p/firework/dev")
    }
}

dependencyResolutionManagement {
    repositories {
        maven("https://packages.jetbrains.team/maven/p/firework/dev")
    }
}

FAQ

I'm developing an Android-only app without Kotlin Mutliplatform. Can I use Compose Hot Reload?

Compose Hot Reload is designed to work with Compose Multiplatform. To use Compose Hot Reload with an Android-only project, you need to:

• Switch from the Jetpack Compose plugin to the Compose Multiplatform plugin.
• Add a separate Gradle module and configure the JVM target according to the instructions.

My project is a desktop-only app with Compose Multiplatform. Can I use Compose Hot Reload?

Yes! However, be aware that you can't start the application via the run button in the gutter (CMP-3123). Instead, use Gradle tasks.