Mobile development often feels like solving the same problem twice—once for Android and again for iOS. It’s time-consuming, repetitive, and not always efficient. Kotlin Multiplatform (KMP) is changing that. It’s a pragmatic solution for teams that want to share core logic across platforms without giving up the performance or feel of native apps.
Instead of forcing a single approach for everything, KMP lets you reuse what matters—like business logic and networking—while still building user interfaces with the tools developers already know and trust. It’s not about replacing native development; it’s about making it smarter and faster.
What is Kotlin Multiplatform?
Kotlin Multiplatform is a development framework created by JetBrains that lets you write shared code in Kotlin and use it across Android, iOS, desktop, and even the web. But here’s the key difference: it doesn’t try to unify everything under one stack. Instead, it focuses on the parts of your app that don’t need to be rewritten for every platform—things like data models, API clients, and business rules.
That means your team can collaborate on one codebase for the logic, and still use Swift for iOS UI or Jetpack Compose for Android. It’s a flexible middle ground that balances speed with control.
Why Developers Are Looking for a Different Cross-Platform Approach
Most cross-platform tools promise “write once, run anywhere,” but reality usually falls short. Apps end up feeling sluggish or unfamiliar, and you spend more time wrestling with limitations than building features. Developers want to reuse code, yes—but not at the cost of performance or platform conventions.
Kotlin Multiplatform offers a different angle. It acknowledges that some parts of the app should be different on each platform, especially the user interface. By letting you share logic where it makes sense, KMP avoids the trade-offs that come with trying to force a one-size-fits-all solution.
Why Kotlin Multiplatform Stands Out
What sets KMP apart is its selective sharing approach. You’re not locked into a specific framework or forced to abandon native tools. You get to keep using Xcode and Swift for iOS, Android Studio for Android, and just plug in shared Kotlin code where it fits.
Another advantage: KMP compiles to native code. There’s no JavaScript bridge or interpreter layer slowing things down. Your logic runs directly on the device, delivering smooth performance and full access to platform APIs.
Inside a Typical KMP Project
A Kotlin Multiplatform project is structured in a way that’s both simple and scalable:
- Shared module (commonMain): This is where all your shared code lives—like data models, repositories, and business logic.
- Platform-specific modules (androidMain and iosMain): These handle anything unique to Android or iOS.
- Gradle build system: This ties everything together, helping you manage dependencies and targets across platforms.
Because of this clear separation, your team can divide responsibilities cleanly. Backend logic can be built and tested independently of the UI, which speeds things up and reduces bugs.
How KMP Compares to Other Tools
Frameworks like Flutter and React Native aim to handle everything, from business logic to UI. That works well for some teams—but not all. The downside is that you often sacrifice native performance, rely on a virtual machine or JS bridge, and end up fighting the framework when you need something custom.
Kotlin Multiplatform doesn’t have that issue. It doesn’t try to replace the native UI layer; instead, it complements it. That gives your app the best of both worlds: shared backend logic and native UI components that look and feel right on each platform.
Reusing Code Where It Counts
One of the biggest time sinks in mobile development is rewriting the same logic for two platforms. API handling, form validation, data parsing—it all ends up duplicated. That’s where Kotlin Multiplatform shines. It lets you write this logic once and share it, cutting down on repetitive work and reducing the chances of introducing inconsistencies.
Imagine having your entire data layer—repositories, API clients, and serialization—all written in a single Kotlin module. Then, both your Android and iOS apps use that same logic. That’s not just convenient; it’s powerful. It means fewer bugs, easier testing, and a smoother development experience for everyone involved.
Adopting Kotlin Multiplatform Without Starting From Scratch
You don’t have to rebuild your app to use KMP. In fact, one of its best features is how easy it is to adopt gradually. If you’ve got a stable Android app or an iOS codebase you don’t want to disrupt, you can still bring in shared modules incrementally.
Start small—maybe with a network layer or a shared authentication flow. Once your team gets comfortable with the workflow, you can expand the shared logic to cover more ground. This gradual rollout approach means less risk, smoother onboarding, and minimal disruption to your existing processes.
A Look Under the Hood: Technical Architecture
Kotlin Multiplatform projects follow a modular design that keeps things clean and organized:
- The commonMain source set holds all the shared code—anything that should behave the same across platforms.
- The androidMain and iosMain source sets are where you plug in platform-specific details when necessary.
- You use Kotlin’s expect/actual keyword mechanism to define platform-dependent behavior in a clean, maintainable way.
This structure gives you full control over what’s shared and what’s native, which is exactly what makes KMP so appealing for real-world teams balancing speed and quality.
Tools You’ll Need to Get Started
Getting started with Kotlin Multiplatform doesn’t require a huge toolchain shift. Most developers already have what they need:
- Android Studio or IntelliJ IDEA for writing and managing Kotlin code.
- Xcode for building and testing iOS components.
- Gradle with the Kotlin Multiplatform plugin for handling builds and dependencies.
The setup process is well-documented and supported by JetBrains, and once you’ve done it once, setting up future projects becomes second nature.
Writing Shared Logic with Modern Kotlin Tools
KMP works beautifully with popular Kotlin libraries, making it easier to share robust, testable logic. A few standouts:
- Ktor for building HTTP clients that work across platforms.
- Kotlinx.serialization for handling JSON and other formats.
- SQLDelight or Realm for database operations in shared code.
These tools allow you to write elegant, type-safe code that works reliably no matter where it runs. The result? Cleaner architecture, fewer bugs, and faster delivery.
What About the User Interface?
Unlike some cross-platform tools, Kotlin Multiplatform doesn’t try to unify the UI layer. And that’s a good thing. The UI is where each platform shines with its own design language and user expectations.
Instead of forcing one UI framework across platforms, KMP encourages using native components—SwiftUI for iOS, Jetpack Compose or XML for Android. You can still keep your logic centralized and shared, while giving users a UI that feels familiar and polished.
If you’re aiming for consistency across platforms, you can still coordinate the look and feel by aligning design systems and component behaviors. But with KMP, you’re never locked into an unnatural one-size-fits-all approach.
Testing and Debugging with Kotlin Multiplatform
Testing shared logic is one of the biggest advantages of using Kotlin Multiplatform. Since your core code runs in a common module, you can write unit tests once and apply them across platforms. No more duplicating test suites for Android and iOS.
For platform-specific code, you can still use the tools you’re already familiar with: JUnit or Espresso for Android, XCTest for iOS. But having a large portion of the app’s functionality covered by shared tests gives you better confidence in your codebase and simplifies CI workflows.
Debugging is also fairly straightforward. Android developers can use standard debugging tools in Android Studio, while iOS developers can integrate the shared module and inspect behavior using Xcode. And as tooling improves, this cross-platform debugging experience continues to get smoother.
Where Kotlin Multiplatform Really Shines
Kotlin Multiplatform is a great fit for projects where the backend logic is complex and needs to behave identically across platforms. Some ideal use cases include:
- Startups building MVPs that need to iterate quickly on Android and iOS without doubling engineering effort.
- Apps with heavy data processing or business logic, where consistency is more important than shared UI.
- Companies with existing native apps looking to reduce long-term maintenance by sharing select features.
It’s not an all-or-nothing proposition—you can start small and scale the shared codebase as your app evolves.
What to Watch Out For
No tool is perfect, and Kotlin Multiplatform has its limitations. The biggest learning curve usually comes from setting up the project structure and handling platform-specific differences. Newcomers might need some time to get used to the expect/actual pattern and managing dependencies across multiple build systems.
Tooling has come a long way, but some rough edges still exist, especially around iOS integration. Swift interop works well, but occasional manual tweaks might be needed to smooth out compatibility or optimize performance.
The good news is that the community is active, documentation is improving rapidly, and JetBrains is continually refining the developer experience.
The Kotlin Multiplatform Ecosystem
The ecosystem around KMP is growing fast. There are libraries specifically built for cross-platform projects, including:
- Koin and Kodein for dependency injection
- Moko libraries for handling things like permissions, resources, and MVVM architecture
- Multiplatform Settings for key-value storage
There’s also strong support from the Kotlin community, with open-source projects, tutorials, and sample apps that help developers ramp up quickly. If you run into an issue, chances are someone else has tackled it and shared their solution.
Looking Ahead: The Future of KMP
JetBrains continues to invest heavily in Kotlin Multiplatform, and its roadmap looks promising. Recent updates have improved memory management, reduced build times, and enhanced Swift interop—making it more production-ready than ever.
As more teams adopt KMP and contribute back to the ecosystem, we’re likely to see even better tooling, stronger libraries, and more use cases. It’s becoming increasingly clear that KMP isn’t just a niche experiment—it’s a practical option for modern cross-platform development.
Main Key Takeaways
- Kotlin Multiplatform lets you share business logic across platforms without sacrificing native performance or experience.
- You can adopt KMP incrementally, making it a low-risk option for modernizing existing codebases.
- Shared testing, fewer bugs, and less duplicated effort lead to more efficient teams and faster delivery.
- Native UIs are preserved, meaning you don’t have to compromise on design or responsiveness.
- The ecosystem is growing, and the tooling continues to improve with each Kotlin release.
Frequently Asked Questions
Can I build UIs with Kotlin Multiplatform?
Not directly. KMP focuses on sharing logic. You’ll still build UIs using native tools like SwiftUI or Jetpack Compose.
Is Kotlin Multiplatform stable enough for production?
Yes, especially for sharing non-UI code. Many teams are using KMP in production for networking, data handling, and shared logic.
How is it different from Flutter or React Native?
Flutter and React Native aim to unify the UI layer. KMP focuses on code reuse where it counts—behind the scenes—while keeping native UI intact.
What platforms does KMP support?
Android and iOS are the most common, but it also supports desktop (macOS, Windows, Linux) and web via Kotlin/JS.
