Kotlin Multiplatform
Kotlin Multiplatform app development company for shared Android and iOS code
We are a Kotlin Multiplatform app development company that shares the parts of your app that should be identical on Android and iOS, such as business rules, networking, data and sync, while keeping the interface native where users notice. It is one of the four routes compared on our cross-platform app development page; this page goes one level deeper into how KMP projects are scoped, structured and run.
Most of our KMP work starts from a good Android app in Kotlin that now needs an iOS version without a second team rewriting the same logic in Swift.
- Shared logic, native UI by default
- Compose Multiplatform where it fits
- Swift-friendly APIs for iOS developers
- Incremental adoption in existing apps
What Kotlin Multiplatform shares, and what stays native
Kotlin Multiplatform (KMP) compiles one Kotlin codebase to Android (on the JVM) and to iOS (as a native framework your Xcode project imports). JetBrains declared KMP stable and ready for production with Kotlin 1.9.20 in November 2023. UI sharing came later: Compose Multiplatform for iOS reached stable in version 1.8.0 in May 2025.
That gives you a choice other frameworks do not. You can share only the logic and build each interface natively in Jetpack Compose and SwiftUI. Or you can share the UI as well, with Compose Multiplatform, and drop to native views for the screens that need them. Flutter and React Native assume you share the UI. KMP lets you decide screen by screen.
Three ways to use KMP
We recommend one of these in writing during discovery, with the reasons.
| Approach | What is shared | Best for | Watch out for |
|---|---|---|---|
| Shared logic, native UI | Models, validation, networking, storage, sync, analytics events | Apps where iOS users expect a true SwiftUI feel; teams with iOS and Android developers | Two UI codebases still need design, build and testing |
| Shared logic plus Compose Multiplatform UI | Most screens as well as logic | Internal tools, B2B apps and products with a strong custom design system | iOS-specific conventions must be designed in; smaller library ecosystem for shared UI |
| Hybrid | Logic everywhere, shared UI on simpler screens, native UI on key flows | Consumer apps that want speed on settings and forms but native polish on the core loop | Clear rules on which screens go where, or the codebase drifts |
Platform-only features such as widgets, Live Activities, Apple Watch and Wear OS apps are written in Swift or Kotlin in every approach.
When KMP is the right call, and when it is not
KMP fits best when you already have Kotlin skills or an Android codebase, when iOS and Android must behave identically on complex rules (pricing, eligibility, offline sync, encryption), and when you still want native UI. Fintech, logistics, health and field-service apps with heavy domain logic tend to get the most out of it.
It is a weaker fit for a brand-new consumer MVP with a small budget and no Kotlin team, where Flutter usually ships both stores faster. It is also weaker if your developers come from React web work, where React Native reuses more of what they know. For a side-by-side with Flutter, read Kotlin Multiplatform vs Flutter.
Signs KMP will pay off
- A working Android app in Kotlin and no iOS app yet
- Business rules that have already drifted between two native apps
- Offline sync or local encryption that must match on both platforms
- An iOS team that wants to keep SwiftUI
- A long product life, so shared logic is maintained once for years
Adding iOS to an existing Android app with KMP
This is the most common KMP project we scope. The Android app keeps shipping throughout.
Module audit
We map which Android code is pure Kotlin and which depends on Android APIs. Pure logic moves first. Anything tied to Android framework classes needs an interface and two implementations.
Extract the shared module
Models, use cases, repositories and API clients move into a shared module. Android-only libraries are swapped for multiplatform ones, for example Ktor for networking and SQLDelight for local storage, where the existing choices do not support iOS.
Platform code through expect/actual and interfaces
Secure storage, biometrics, file access and platform SDKs get a common interface with Android and iOS implementations. We prefer plain interfaces with dependency injection, and use expect/actual declarations sparingly.
Swift-friendly API layer
Kotlin coroutines and flows do not look natural from Swift on their own. We design the shared API so iOS developers get clean async functions and observable state, and we review it with them before the iOS screens are built.
Build the iOS app
SwiftUI or Compose Multiplatform screens on top of the shared module, with a TestFlight build every two-week sprint alongside the usual Play Console internal testing build.
Shared tests and CI
Business logic tests run once in the shared module and execute on both targets. CI builds the Android app and the iOS framework on every pull request, on GitHub Actions macOS runners or Codemagic, which supports KMP.
Have an Android app and need iOS?
Share read access to the repository. We will tell you how much of the code can move into a shared module and the next step to a fixed quote, and we reply within one business day.
Architecture choices that decide whether KMP works
KMP projects succeed or fail on boundaries. The shared module should own state and rules, and expose them through a small, stable API. When UI code reaches into shared internals, every change becomes a two-platform change and the benefit disappears.
Dependencies
Every library in the shared module must support every target. We check this before committing to a design, because a single Android-only dependency deep in the data layer can block the iOS build. Where no multiplatform library exists, we wrap the native SDKs behind an interface.
Concurrency and memory
Shared code uses Kotlin coroutines. On iOS, long-running flows must be cancelled when screens disappear, or they leak. We test memory on real iPhones with Xcode Instruments, not just in the simulator.
Build times and binary size
Kotlin/Native compilation is slower than a JVM build, and the shared framework adds to the iOS app size. We set up Gradle caching and measure the iOS binary from the first sprint, so neither surprises you at release.
What our Kotlin Multiplatform app development company builds
Typical KMP projects, from small shared modules to full apps.
iOS from an Android app
The project above: share the domain and data layers of a mature Android app and build the iOS app on top.
New apps with shared logic
Greenfield apps with native UI on each platform and one shared core. Good when you have, or will hire, both Android and iOS developers.
Shared SDKs
A single Kotlin library for payments, sync, encryption or device communication, published to both your Android and iOS apps or to partners.
Compose Multiplatform apps
Shared UI for internal tools, B2B dashboards and design-system-led apps, with native screens where the platform matters.
Consolidating two native apps
Two existing native apps whose rules have drifted. We move one feature at a time into shared code and delete the duplicate.
Code review and rescue
KMP projects where builds are slow, the iOS side feels second-class, or the shared module has turned into a tangle. We audit and fix the boundaries.
Team, hiring and maintenance implications
KMP needs Kotlin skills for the shared code and at least one developer comfortable with Xcode and Swift for the iOS side. That is the main cost difference from Flutter: you share logic, not people. In return, your iOS app is a normal Xcode project, and an iOS specialist can work in it without learning a new UI framework.
If you have a product team and need capacity, you can hire Kotlin developers with KMP experience on a dedicated or staff-augmentation basis, with a two-week trial. Every project runs under NDA, in your repository, and you own the code and store accounts from day one.
Kotlin Multiplatform projects we have delivered
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Kotlin Multiplatform app development company FAQs
Is Kotlin Multiplatform ready for production?
Yes. JetBrains declared Kotlin Multiplatform stable and ready for production use with Kotlin 1.9.20 in November 2023, and Compose Multiplatform for iOS reached stable in version 1.8.0 in May 2025. Some advanced language features were still marked non-stable at that point, so we check the status of anything we rely on during discovery.
Does Kotlin Multiplatform share the UI as well as the logic?
It can. By default KMP shares business logic, networking and data, and each platform keeps its own UI in Jetpack Compose and SwiftUI. With Compose Multiplatform you can share the UI too. Many apps mix both, sharing simpler screens and keeping native UI for the flows users care most about.
Can we add Kotlin Multiplatform to our existing Android app?
Yes, and that is the most common starting point. We move pure Kotlin code such as models, rules and API clients into a shared module, replace Android-only libraries where needed, and build the iOS app on top. The Android app keeps shipping while this happens, with no feature freeze.
Kotlin Multiplatform or Flutter: which should we choose?
Choose KMP if you already have Kotlin skills or an Android app, want native UI, or have complex shared rules. Choose Flutter if you are starting fresh, want one team writing one UI for both platforms, and want the fastest route to both stores. Our Kotlin Multiplatform vs Flutter guide compares them in detail.
Do iOS developers like working with Kotlin Multiplatform?
They do when the shared API is designed with them. Raw Kotlin coroutines and flows feel awkward from Swift, so we design async functions and observable state that read naturally in Swift, and review the API with the iOS developers. When this step is skipped, the iOS team usually ends up resenting the shared module.
Does Kotlin Multiplatform make the iOS app bigger or slower?
The shared framework adds some size to the iOS binary, and Kotlin/Native builds are slower than JVM builds. Runtime performance of shared logic is generally fine for business apps. We measure binary size and build times from the first sprint and tune Gradle caching, so neither becomes a release-week surprise.
Share the logic, keep the native feel
Book a 30-minute call. We will go through your current codebase and team, tell you whether KMP, Flutter or native fits, and follow up within one business day.