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Kotlin Multiplatform Development
Shares networking, data and business logic between Android and iOS in Kotlin, while each platform keeps its own native interface.
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What Kotlin Multiplatform is
Kotlin Multiplatform (KMP) lets a team write shared code once in Kotlin and compile it for Android, iOS and other targets. Typically the shared layer holds the data models, networking, local storage, validation and business rules, while the interface stays native on each platform: Jetpack Compose on Android and SwiftUI or UIKit on iOS.
This is a different bet from Flutter or React Native. Those share the interface and the logic and draw the same screens on both platforms. KMP shares the logic and leaves the interface native, which keeps the platform look and feel at the cost of building the UI twice. Compose Multiplatform extends KMP to share interface code too, but it is a separate decision with its own maturity trade-offs.
Suitability
And when it is not. Choosing the wrong tool costs more than any implementation detail.
Good fit for
- Products that already have, or want, fully native Android and iOS interfaces but do not want to implement the same business logic twice
- Teams with strong Kotlin and Android experience who want to extend into iOS without adopting a new language for the core logic
- Apps with complex shared rules, offline sync or data layers where a divergence between platforms would cause real bugs
- Gradual adoption in an existing native app, moving one shared module at a time
Consider alternatives for
- Small apps where the shared logic is thin, so the build complexity outweighs the saving
- Teams with no Kotlin experience and a tight timeline, where Flutter or React Native has a shorter learning curve
- Products that want one shared interface across platforms, where a full cross-platform UI framework is the more direct fit
In practice
01
Shared logic under native interfaces
A shared Kotlin module for networking, caching and domain rules consumed by a native Android app and a native iOS app, so a rule change is made once.
02
Introducing KMP into an existing native app
Moving one well-bounded piece, such as an authentication or sync layer, into shared code first, to prove the approach before committing the wider codebase to it.
03
Evaluating KMP against the alternatives
Scoping work that compares KMP, Flutter and React Native for a specific product, with a recommendation based on the team, the interface requirements and the maintenance horizon.
Considerations
Practical notes from running this in production.
- 01
The iOS side is where KMP projects feel friction: calling Kotlin from Swift, handling coroutines and generics across the boundary, and debugging across two toolchains. It is workable, but iOS engineers need to be involved from the start.
- 02
Build tooling and dependency management add a layer that a single-platform project does not have. Build times, CI configuration and version alignment between Kotlin, Gradle and Xcode need real attention.
- 03
Library support is good for networking, serialization, databases and dependency injection, but thinner than for a single platform. We check that the libraries a project needs have multiplatform support before choosing KMP.
- 04
You still pay for two native interfaces. KMP reduces duplicated logic, not duplicated screens, so the saving depends on how much of your app is logic rather than UI.
FAQ
Is Kotlin Multiplatform something you deliver regularly?
Kotlin is part of our mobile stack, and KMP is an extension of it that we take on per engagement. Flutter and React Native are our usual cross-platform choices because they suit most new products. We would recommend KMP specifically where native interfaces matter and shared logic is substantial, and we say so plainly rather than pitching it by default.
Kotlin Multiplatform or Flutter?
Choose KMP when you want fully native interfaces on each platform and only want to share logic. Choose Flutter when you want one codebase for both the interface and the logic and are comfortable with Flutter drawing its own UI. The right answer depends on how much native feel your product needs.
What is the difference between KMP and Compose Multiplatform?
KMP is the mechanism for sharing Kotlin code across platforms, usually the non-UI layer. Compose Multiplatform builds on it to share interface code written in Jetpack Compose across Android, iOS and desktop. You can adopt KMP without Compose Multiplatform, which is the more conservative route.
Can we add KMP to an existing Android or iOS app?
Yes. A common approach is to extract a bounded module, such as networking or a data layer, into shared Kotlin and consume it from both apps, then expand if it works well. We would review the codebase first to see whether that is realistic.
How long does a Kotlin Multiplatform development project take?
It depends on scope. A focused first release is usually weeks rather than months, while larger platforms are delivered in phases. We give a written estimate after a short discovery conversation and agree milestones before work starts.
By industry
Where we apply Kotlin Multiplatform. Tiles marked "Guide" open a dedicated write-up; the rest open the industry page.
Let’s talk about your Kotlin Multiplatform project
Tell us what you are trying to build or fix. We will come back with scope, approach and an honest view on cost and timeline.