compose-multiplatform

Compose Multiplatform is a declarative UI framework from JetBrains that lets you share UI code across iOS, Android, desktop, and (in beta) web using Kotlin. It's built on top of Jetpack Compose, Google's Android UI framework, and extends it across platforms through Kotlin Multiplatform. It's aimed at Kotlin teams that want one UI codebase instead of maintaining separate native UIs per platform.

Because it sits on top of Kotlin Multiplatform rather than replacing it, you keep the option of writing platform-specific code where you need it and sharing everything else. That's a different model from cross-platform frameworks that abstract the underlying platform away entirely. You're still working with Kotlin end to end, on the UI layer as well as any shared business logic.

Key features

• Shared UI across platforms: write UI once in Kotlin and target iOS, Android, desktop, and web from the same codebase, sharing UIs between, for example, iOS and Android or Windows and macOS.
• Shares Jetpack Compose APIs: since it's based on Jetpack Compose, the same declarative APIs used for Android UI apply to iOS as well, so Android Compose experience carries over directly.
• Native API access on iOS: built on Kotlin Multiplatform, so you can call native APIs like the Camera API and embed native UI views such as MKMapView directly inside a Compose UI.
• Hardware-accelerated desktop rendering: targets the JVM with hardware-accelerated UI rendering on Windows, macOS, and Linux.
• Desktop-specific extensions: includes support for menus, keyboard shortcuts, window manipulation, and notification management on desktop targets.
• Web support in beta: the web target is built on Kotlin/Wasm, described as the newest target for Kotlin Multiplatform projects, running compiled code in the browser via WebAssembly with predictable performance.
• Compose HTML: a separate library, targeting Kotlin/JS specifically, for building web UIs with composable HTML and CSS building blocks. The README notes it is not itself a multiplatform library.

Ideal use cases

Compose Multiplatform is a good fit for Kotlin-first teams that want to share UI logic between Android and iOS, or between desktop platforms, without writing and maintaining separate SwiftUI, UIKit, or platform-specific desktop UI code for each target. It's particularly useful when a team already has Android expertise in Jetpack Compose and wants to extend that same skill set and codebase to other platforms rather than starting over.

It's a weaker fit for teams not already invested in Kotlin, or for projects that need production-grade web support today, since the README marks web support as Beta and specifically asks for feedback on it through a public Slack channel. If your only target is the web and you don't need multiplatform sharing, Compose HTML, which is Kotlin/JS only, or a dedicated web framework, may be a more direct choice than the full multiplatform stack.

Installation

The README doesn't include inline setup commands. Instead, it routes everyone, regardless of target platform, to a single getting-started resource:

• General getting started guide, covering iOS, Android, desktop, and web setup: https://jb.gg/start-cmp
• Web-specific getting started guide, linked separately in the README's Web section: https://jb.gg/start-cmp

Additional resources referenced for going further include a FAQ, sample projects, tutorials (in this repository's tutorials/README.md), a compatibility and versioning guide, and a changelog. For help beyond the docs, the project maintains public Slack channels split by platform, #compose-ios, #compose-desktop, and #compose-web, plus a general #compose channel, and a YouTrack tracker for filing issues if you run into problems getting a project set up.

Because setup differs depending on which platforms you're targeting (iOS and Android through Android Studio, desktop through the JVM, web through Kotlin/Wasm), following the guide for your specific combination of targets is more reliable than a single generic set of commands would be.