Kotlin Multiplatform: A Detailed Guide to Cross-Platform Development

In today’s rapidly evolving digital landscape, businesses often face challenges in developing applications for multiple platforms like Android, iOS, desktop, and web. Kotlin Multiplatform (KMP) is an innovative solution designed to streamline cross-platform development while maintaining high performance and native experience. In this article, we will explore how Kotlin Multiplatform works, its benefits, drawbacks, and ideal use cases.

Kotlin Multiplatform: A Game-Changer in Cross-Platform Development

Kotlin Multiplatform (KMP) is an innovative software development kit (SDK) created by JetBrains, designed to streamline multi-platform application development. It allows developers to write shared business logic once and deploy it across various platforms, including Android, iOS, web, and desktop applications, while still retaining full control over the native UI.

Unlike traditional cross-platform frameworks like Flutter and React Native, which enforce a common rendering engine for UI across platforms, KMP embraces a hybrid approach. It enables teams to reuse core functionalities while keeping the user interface (UI) native, ensuring a seamless user experience tailored to each platform’s unique guidelines and design language.

JetBrains introduced Kotlin Multiplatform as part of Kotlin 1.2 in 2017, and despite still being in beta, it has already gained significant traction among leading companies such as Netflix, Philips, Baidu, VMware, and CashApp. This growing adoption highlights its reliability and potential as a versatile cross-platform solution.

Key Features of Kotlin Multiplatform

Kotlin Multiplatform stands out as a unique cross-platform development solution that balances code reusability, performance, and native experience. Unlike other frameworks that enforce a single approach to building applications, KMP provides flexibility in code sharing, allowing developers to write shared business logic while keeping the UI native. This ensures a high-quality user experience without sacrificing development efficiency. Below are the key features that make Kotlin Multiplatform a powerful choice for modern app development.

• Cross-Platform Code Sharing – Developers can share networking, database management, business logic, and analytics while keeping platform-specific implementations where necessary.
• Multi-Device Support – KMP works on Android, iOS, Web, Desktop (Windows, macOS, Linux), and Embedded systems.
• Interoperability with Java, Swift, and Objective-C – KMP integrates smoothly with existing native codebases, making it easy for companies to migrate existing projects.
• Flexible Gradual Migration – Developers can adopt KMP step by step, starting with small modules rather than rewriting entire applications.

Why Are Major Companies Using Kotlin Multiplatform?

Companies like Netflix, Baidu, and VMware have already adopted Kotlin Multiplatform due to its flexibility and ability to reduce redundant development efforts. By enabling partial code sharing, it allows businesses to keep native UI performance while reducing maintenance costs.

For instance, Memrise, a popular language learning app, uses KMP to share logic related to networking and data persistence, while keeping its UI platform-specific. This approach allows them to maintain a responsive and native UI experience, crucial for user engagement.

Kotlin Multiplatform in Action: How It Works and Why It Matters

Kotlin Multiplatform (KMP) enables developers to share business logic across multiple platforms while keeping the UI native. This unique approach allows developers to maximize code reusability without compromising performance or user experience. Below is a detailed breakdown of how Kotlin Multiplatform works, from writing shared code to executing it on different platforms.

1. Writing Shared Code in Kotlin

At the core of Kotlin Multiplatform is the ability to write shared business logic in Kotlin. This includes:

• Networking – API calls, data fetching, and synchronization.
• Data Storage – Database management, shared preferences, and local storage.
• Business Logic – Authentication, algorithms, and data processing.
• Analytics & Logging – Event tracking and error handling.

This shared code is placed in a common module that is accessible by multiple platform-specific implementations. By using Kotlin’s powerful multiplatform capabilities, developers can significantly reduce redundant code, making maintenance easier and development more efficient.

2. How Kotlin Multiplatform Works on Android

Android runs on the Java Virtual Machine (JVM), which means Kotlin code needs to be converted into Java bytecode before execution. Here’s how the process works:

1. The Kotlin Compiler translates Kotlin code into Intermediate Representation (IR).
2. The IR is compiled into Java bytecode, which can be executed by the JVM.
3. The bytecode is packaged into an Android APK and run on Android devices.

Since Android already has a built-in JVM, there is no need for additional runtime environments. This allows for seamless integration with existing Android projects, and developers can use Kotlin Multiplatform without modifying their Android-specific code.

3. How Kotlin Multiplatform Works on iOS

Unlike Android, iOS does not support Java bytecode and does not have a virtual machine like the JVM. Instead, Kotlin Multiplatform uses Kotlin/Native, which allows Kotlin code to be compiled into machine-executable native code.

Here’s how Kotlin Multiplatform enables code execution on iOS:

1. Kotlin Code → Intermediate Representation (IR): The Kotlin compiler first converts the Kotlin code into IR, a common intermediate format that can be further processed for native execution.
2. IR → Native Code Using Kotlin/Native: Since iOS does not support virtual machines, the Kotlin code needs to be fully compiled into a format that can run directly on an iOS device. This is done using LLVM (Low-Level Virtual Machine), which translates the IR into iOS-native machine code.
3. Integration with iOS Frameworks: The compiled Kotlin/Native code can then be packaged as an iOS framework that can be seamlessly integrated into Xcode projects. Developers can call the shared Kotlin logic from Swift or Objective-C code just like they would with any other native framework.

This approach ensures that iOS apps built with Kotlin Multiplatform run at native performance levels and are fully compatible with iOS development tools and libraries.

4. The Role of the Kotlin Compiler in Multiplatform Development

The Kotlin compiler plays a crucial role in transforming Kotlin code into platform-specific executable formats. It consists of two main components:

• Frontend Compiler: Converts Kotlin source code into Intermediate Representation (IR). This IR is a universal format that allows the code to be compiled into different target platforms.
• Backend Compiler: Translates IR into platform-specific code: For Android: Converts IR into Java bytecode, which runs on the JVM. For iOS: Uses LLVM to generate native machine code that runs on iOS devices.

This two-step compilation process ensures that Kotlin code remains flexible and adaptable to different platforms without requiring major modifications.

5. Execution on Different Platforms

Kotlin Multiplatform allows the same core business logic to run on different operating systems while preserving native UI development. Here’s how execution happens on various platforms:

• Android Execution Process: Kotlin code is compiled into Java bytecode. The bytecode runs on Android’s JVM without requiring any additional runtime. The final output is a fully functional Android app with native UI.
• iOS Execution Process: Kotlin code is compiled into Intermediate Representation (IR). The IR is converted into iOS-native machine code using LLVM. The final output is an iOS framework that integrates seamlessly with Swift or Objective-C code.
• Web & Desktop Execution: For web applications, Kotlin Multiplatform can transpile Kotlin code into JavaScript. For desktop applications, Kotlin code is compiled into executable binaries for Windows, macOS, or Linux.

This method ensures that businesses can leverage the same core logic across multiple platforms while keeping their user interfaces native and fully optimized for each operating system.

6. The Advantage of Keeping UI Native

One of the biggest advantages of Kotlin Multiplatform is that it does not enforce a single UI framework across platforms. Instead, it allows developers to reuse only the business logic while keeping the UI native.

Key benefits of this approach:

• Better Performance – Unlike Flutter or React Native, there’s no extra rendering layer, resulting in faster, more responsive apps.
• Native Look & Feel – Each platform retains its unique UI elements, making the app more intuitive for users.
• Flexible Design Choices – Developers are not restricted to using a single UI framework and can integrate Kotlin Multiplatform into existing native projects.

For example, an Android app can continue using Jetpack Compose or XML-based layouts, while the iOS version uses SwiftUI or UIKit, ensuring the best possible experience for each platform’s users.

Why Choose Kotlin Multiplatform? Key Advantages for Modern App Development

Kotlin Multiplatform (KMP) stands out among cross-platform development solutions by offering a unique balance of flexibility, performance, and code reusability. Unlike other frameworks that enforce a single development approach, KMP allows businesses to selectively share code while keeping platform-specific elements independent. This results in faster development, improved efficiency, and a high-quality user experience across multiple platforms. Below, we explore the key benefits of Kotlin Multiplatform in detail.

1. Selective Code Sharing: Full Control Over What to Share

One of the most significant advantages of Kotlin Multiplatform is its flexibility in code sharing. Unlike other cross-platform solutions such as Flutter or React Native, which require a single codebase for everything, KMP allows developers to decide which parts of their application should be shared and which should remain platform-specific.

• Developers can reuse business logic, such as networking, database operations, analytics, and security features, while keeping the UI and platform-specific functionalities native.
• If an app already exists on one platform, KMP enables incremental adoption, meaning developers can start sharing small portions of the code instead of rewriting the entire application.
• Teams can continue using existing Android (Jetpack Compose) and iOS (SwiftUI or UIKit) UI frameworks, ensuring a seamless user experience.

This selective approach reduces technical risks and improves maintainability, making Kotlin Multiplatform a great fit for complex applications that require native-level performance.

2. Enhancing Native App Development Without a Full Rewrite

Many businesses have already built native applications for Android and iOS using separate codebases. Unlike traditional cross-platform tools that require a complete rewrite to unify development, Kotlin Multiplatform can be introduced gradually into existing native projects.

• Developers can start by sharing smaller modules such as API clients, authentication mechanisms, or business logic, without affecting the existing platform-specific UI.
• Companies don’t need to discard their current native apps; instead, they can enhance them by integrating shared Kotlin code progressively.
• This approach allows businesses to reduce duplicate effort over time, while still benefiting from the performance and user experience of native applications.

By providing the ability to expand and optimize existing apps, Kotlin Multiplatform is an ideal solution for businesses looking to future-proof their mobile applications while maintaining full control over platform-specific features.

3. Faster Development and Cost Efficiency

One of the main reasons businesses adopt cross-platform solutions is to reduce development time and costs. Kotlin Multiplatform significantly accelerates development cycles by eliminating redundant work across platforms.

• Developers write business logic once, reducing the need to duplicate code for Android and iOS.
• 30-50% faster development cycles have been reported in projects using KMP, as teams avoid repetitive coding and testing efforts.
• Reduced maintenance costs – Bug fixes and feature updates are applied to the shared codebase, ensuring that both Android and iOS apps stay in sync without additional effort.
• Since Kotlin is already the preferred language for Android development, existing Android developers can easily transition into KMP, reducing the need to hire additional specialists.

By minimizing the need for separate development teams and optimizing workflows, Kotlin Multiplatform helps businesses bring their applications to market faster and at a lower cost.

4. Improved Collaboration Between Android and iOS Teams

One of the biggest challenges in mobile app development is the communication gap between Android and iOS development teams. Kotlin Multiplatform promotes better collaboration by enabling teams to work together on shared logic while still handling UI separately.

• Clear division of tasks – The Android team can work on business logic while the iOS team focuses on UI, or vice versa.
• Code consistency – Since both teams work with the same shared Kotlin code, differences in implementation logic are minimized.
• Faster feature development – The shared code can be developed and tested once, rather than independently on both platforms, reducing misalignment between Android and iOS versions.

This results in a more streamlined development process, improved communication between teams, and a more consistent application architecture.

5. Architectural Consistency Across Platforms

One of the biggest issues with developing separate native applications for Android and iOS is the potential for inconsistencies in architecture, logic implementation, and feature updates. With Kotlin Multiplatform, these inconsistencies are minimized.

• Unified business logic ensures consistency, meaning features behave the same way across all platforms.
• Reduced risk of platform-specific bugs – Fixes applied to the shared codebase are reflected across all platforms, improving reliability.
• Easier debugging and maintenance – Instead of tracking issues separately for Android and iOS, developers can identify and resolve problems once in the shared code.

By enforcing a common architecture, Kotlin Multiplatform helps businesses maintain a higher-quality product that behaves predictably across all devices.

6. Strong Industry Support and Growing Developer Community

Kotlin Multiplatform has gained strong backing from JetBrains and Google, making it one of the most promising cross-platform technologies available today. As more companies adopt KMP, the ecosystem is expanding, providing better tools, libraries, and community-driven solutions.

• Google officially supports Kotlin as the primary language for Android, making it a natural choice for developers looking to build cross-platform applications.
• Leading tech companies such as Netflix, VMware, Baidu, and CashApp are already using Kotlin Multiplatform in production applications.
• The open-source community around Kotlin Multiplatform is growing, meaning more libraries, documentation, and best practices are becoming available.

As KMP moves toward full stability, it is expected to become an even more robust solution for businesses looking to adopt a flexible cross-platform approach.

 

Limitations of Kotlin Multiplatform: Challenges to Consider

While Kotlin Multiplatform (KMP) offers numerous advantages, it is not without its challenges. Despite its flexibility and ability to share business logic across platforms, there are still technical and ecosystem-related limitations that developers need to consider before adopting KMP for their projects. Below, we explore the key drawbacks of Kotlin Multiplatform in detail.

1. Libraries Are Still Evolving

Kotlin Multiplatform provides a growing selection of libraries for essential development tasks such as networking, data storage, JSON parsing, concurrency, logging, and testing. However, its ecosystem is still relatively young compared to more mature cross-platform frameworks like Flutter and React Native.

Key ch€€allenges related to libraries:

• Limited third-party support: Many popular third-party libraries used in native development for Android (Java/Kotlin) and iOS (Swift/Objective-C) do not yet offer Kotlin Multiplatform support. This means developers often need to write custom wrappers to integrate them into their projects.
• Early-stage libraries: While key functionalities such as HTTP networking (Ktor), database access (SQLDelight), and serialization (Kotlinx.serialization) are available, they lack the extensive community support and documentation found in frameworks like React Native or Flutter.
• Additional effort for native integrations: If a feature requires deep platform-specific functionality (e.g., camera access, Bluetooth, AR, or advanced animations), developers often need to write custom native code in Swift or Kotlin, making implementation more complex.

Impact: For projects that rely heavily on third-party libraries or advanced platform-specific integrations, Kotlin Multiplatform may require additional development effort, increasing project complexity and potential delays.

2. No Built-in UI Sharing: Separate UI Development for Each Platform

Unlike Flutter or React Native, which provide a unified UI framework for cross-platform development, Kotlin Multiplatform only shares business logic. UI development must still be implemented separately for each platform using native tools.

Current UI implementation requirements:

• Android: UI must be created using Jetpack Compose or traditional XML layouts.
• iOS: Developers must use SwiftUI or UIKit for UI design.
• Desktop/Web: UI must be implemented separately using Compose for Desktop or JavaScript frameworks for web applications.

Why is this a limitation?

• Increased development effort: Since UI code is not shared, developers must still build and maintain separate UI components for each platform.
• No automatic design consistency: Unlike Flutter, which enforces a uniform UI across platforms, KMP does not guarantee visual consistency between Android and iOS apps.
• Higher skill requirements: Teams working with KMP need developers who are familiar with both Android UI frameworks (Jetpack Compose/XML) and iOS UI frameworks (SwiftUI/UIKit).

Potential solutions in the future:

JetBrains is actively working on Compose Multiplatform, which aims to provide a shared UI framework for desktop and mobile applications. However, at present, Compose for iOS is not production-ready, making UI sharing across platforms a challenge.

Impact: For projects that prioritize a fully shared UI experience, Kotlin Multiplatform may not be the best choice unless teams are comfortable with maintaining separate UI implementations for each platform.

3. Limitations with Swift and Objective-C Interoperability

Kotlin Multiplatform allows developers to write shared business logic in Kotlin and use it within iOS applications through Kotlin/Native. However, the transition from Kotlin to Swift/Objective-C is not always seamless, and certain Kotlin features do not translate well into iOS code.

Key limitations with Swift and Objective-C compatibility:

• Default parameters in Kotlin are not supported in Objective-C. If a Kotlin function has default parameters, they will not work correctly in Objective-C, requiring overloaded function versions as a workaround.
• Kotlin generics behave differently in Objective-C. Some generic types in Kotlin may not be recognized properly in Swift or Objective-C, leading to additional complexity when working with shared data models.
• Nullable types can cause issues. Kotlin’s null safety system does not always map perfectly to Objective-C, which lacks the same level of null safety, leading to potential runtime errors if not handled correctly.
• Memory management differences: Kotlin/Native uses automatic reference counting (ARC) on iOS, but memory management behaviors can differ from Swift, sometimes leading to unexpected memory leaks or crashes.

Workarounds for Swift integration issues:

• Writing additional Swift wrappers around Kotlin code to handle type mismatches and default parameters.
• Using explicit Objective-C-compatible types instead of relying on Kotlin’s type system.
• Carefully testing Kotlin/Native implementations in real iOS environments to catch unexpected behavior.

Impact: While Kotlin/Native enables business logic sharing on iOS, its interaction with Swift and Objective-C requires additional attention, which can slow down development and increase complexity.

4. Challenges in iOS Development with Kotlin Multiplatform

Since Kotlin was originally designed for JVM-based environments, Kotlin/Native for iOS is still evolving and has some challenges when compared to Swift or Objective-C.

Key iOS development challenges with KMP:

• Lack of Swift-specific features: While Kotlin/Native integrates with iOS, it does not fully support Swift-specific capabilities such as property wrappers, async/await syntax, or SwiftUI bindings.
• Longer build times: Compiling Kotlin/Native code for iOS takes longer than standard Swift builds, which can slow down development cycles.
• Debugging Kotlin code in Xcode is limited: Since Kotlin/Native does not run in a virtual machine (like Java on Android), debugging shared code in Xcode is less intuitive compared to debugging Swift code.
• Concurrency differences: Kotlin uses coroutines, while Swift uses Grand Central Dispatch (GCD) and async/await, making concurrency management across platforms more complex.

Potential future improvements:

JetBrains is actively working on improving Swift compatibility and enhancing Kotlin/Native’s performance for iOS applications. However, these challenges mean that for now, iOS development with Kotlin Multiplatform requires additional effort and expertise.

Impact: For teams with strong Swift experience, transitioning to Kotlin/Native for iOS development may require additional learning and adjustments to existing workflows.

While Kotlin Multiplatform offers unparalleled flexibility in cross-platform development, it still has certain limitations that developers must consider.

Mobian and Kotlin Multiplatform: Building Scalable Cross-Platform Applications

Mobian is a software development company specializing in cross-platform mobile and web solutions. With expertise in Kotlin Multiplatform (KMP), we focus on building scalable applications that share core logic while maintaining native performance across Android and iOS. Our approach enables businesses to streamline development processes, reduce costs, and deliver high-quality applications that meet industry-specific requirements in fields such as FinTech, MedTech, and enterprise solutions.

Kotlin Multiplatform in Our Development Process

Kotlin Multiplatform allows us to write shared code for key application components such as business logic, data management, and network communication, while keeping platform-specific implementations where necessary. This ensures a balance between code reusability and native performance. By adopting KMP, we:

• Reduce redundancy by minimizing duplicated code across multiple platforms.
• Enhance maintainability with a unified codebase that simplifies updates and feature enhancements.
• Ensure platform-native user experiences while benefiting from shared business logic.
• Optimize performance by integrating native APIs when needed for platform-specific functionalities.

Advancing Cross-Platform Development with KMP

As Kotlin Multiplatform continues to evolve, Mobian remains committed to leveraging its capabilities for efficient and scalable application development. Our experience with KMP allows us to create flexible and future-proof solutions tailored to the needs of businesses looking for reliable cross-platform applications.

 

Conclusion

Kotlin Multiplatform provides a powerful and efficient way to build full-stack applications that run seamlessly on Android, iOS, and desktop. By leveraging Ktor for backend services and Compose Multiplatform for shared UI, developers can create applications with a single codebase while maintaining native performance and platform-specific optimizations. This not only reduces development time but also ensures consistency across platforms, minimizing potential errors and maintenance efforts.

With the Kotlin Multiplatform Wizard, developers can quickly set up projects that integrate server-side and client-side logic, share data models, and streamline API communication using Ktor. As the ecosystem evolves, Kotlin Multiplatform continues to simplify cross-platform development, making it a compelling choice for modern applications that require efficiency, scalability, and maintainability.