In mobile app development, developers and tech leads are always looking for ways to balance efficiency, maintainability, and performance. 

Kotlin Multiplatform Mobile (KMM) has emerged as a practical solution for code-sharing between Android and iOS, allowing developers to reuse business logic (such as video playback rules, content APIs, caching, analytics, or DRM flows) while keeping platform-specific implementations for UI or media handling when needed.

This article examines KMM’s advantages and trade-offs, compares it with traditional platform-specific API integration, and explores when it’s most effective – particularly for use cases in streaming applications, where performance, scalability, and platform-specific UI flexibility are critical.

To illustrate this, we walk through a real-world example of API integration in a KMM project, contrasted with separate implementations in native Android and iOS codebases.

How KMM achieves code sharing 

Shared Code: Business logic, networking, data models, and other core code are written in Kotlin and compiled into platform-specific binaries (a Kotlin library for Android, a Kotlin framework for iOS.

Platform-Specific Code: UI and platform-specific APIs (e.g., camera, GPS, notifications) remain implemented in native languages Swift/Objective-C for iOS, Kotlin/Java for Android).

When to use KMM 

• Applications with Shared Business Logic: Apps that rely heavily on network requests, data processing, and caching benefit from KMM’s shared code. 
• Enterprise Applications: Businesses aiming to maintain feature parity across platforms with minimal duplication should consider KMM. 
• Gradual Migration from Native to Cross-Platform: Organisations with existing native applications can integrate KMM incrementally. 
• Apps Requiring High Performance with Native UI: Since KMM allows native UI development, it suits apps that require performance optimisation while reducing duplicated logic.

Use cases: Choosing between KMM and platform-specific API integration 

Let’s understand a use case for API integration and compare the approaches of using KMM versus platform-specific implementations.

Example: API integration in KMM vs. native approach 

One of the major benefits of KMM is the ability to write shared business logic once, including external API calls and reuse it across both Android and iOS platforms. This minimises code duplication and simplifies long-term maintenance.

Below is a comparison of how an external API call is handled using KMM versus platform-specific (native) implementations.

KMM Shared Implementation (Kotlin – Shared Module)

This logic resides in the shared module and can be called from both Android and iOS apps, ensuring consistency and reducing duplicate work. 

Android-Specific Implementation (Kotlin)

In a fully native Android approach, you would build and manage your own Retrofit service for API calls.

iOS-Specific Implementation (Swift)

On the iOS side, you’d typically use URLSession with Codable to perform the same task.

Key takeaways from the example 

• KMM allows a single API implementation, reducing duplication.
• Separate API integration requires maintaining two different implementations in Swift and Kotlin.
• Debugging and maintaining one API implementation in KMM is simpler and cost-effective compared to handling two codebases.

How to start with KMM

• Create a KMM Module: Set up a new KMM module in Android Studio, with shared code in commonMain, and platform-specific code in androidMain and iosMain.
• Configure Android Integration: Add the KMM module as a dependency in build.gradle and use shared functions in Android.
• Configure iOS Integration: Build the KMM module into a .framework and integrate it into Xcode.
• Test and Optimise: Ensure smooth communication between Kotlin and Swift, and use logging tools for debugging.

KMM  Compose vs. other cross-platform frameworks 

When building mobile apps, teams are often faced with a key decision: how to build them for both Android and iOS efficiently, without compromising on performance or user experience.

This is where cross-platform frameworks like Flutter, React Native, and Kotlin Multiplatform Mobile (KMM) with Jetpack Compose come into play.

The comparison below explores how KMM + Jetpack Compose stacks up against Flutter and React Native in these key areas highlighting where each shines and which may be best suited depending on project goals.

Advantages of KMM

• Code Reusability & Faster Development: KMM enables developers to write business logic once and share it across platforms, reducing redundant work. This speeds up development while ensuring a single source of truth for API calls, data processing, and caching.
  
• Native Performance & UI Flexibility: Unlike other cross-platform frameworks, KMM allows developers to build fully native UIs using Jetpack Compose for Android and SwiftUI/UIKit for iOS, ensuring a smooth and optimised user experience.
  
• Seamless Integration with Existing Projects: KMM can be introduced incrementally into native projects without requiring a full rewrite. It works alongside existing Android and iOS codebases, making it ideal for teams transitioning from native to shared logic.
  
• Interoperability & Platform-Specific Access: KMM compiles to native code, allowing direct interaction with platform-specific APIs and third-party libraries. This ensures seamless integration with Android and iOS features while maintaining high performance.

Disadvantages of KMM

• Limited iOS Support and Learning Curve: While Kotlin has extensive support for Android, iOS support is still growing. Some third-party Kotlin libraries may not be fully compatible with iOS, requiring custom implementations. Additionally, iOS developers unfamiliar with Kotlin may require additional time to adapt.
  
• Build Complexity and Debugging Challenges: Managing Gradle for Kotlin code and Xcode for Swift-based UI adds complexity. Debugging shared code in iOS requires additional setup, and certain platform-specific functionalities (such as camera or location services) still require native implementations.

Beyond Mobile: The Scope of Kotlin Multiplatform

While KMM is primarily designed for sharing code between Android and iOS, Kotlin Multiplatform (KMP) extends beyond mobile development. KMP enables developers to share code across multiple platforms, including backend (JVM, Ktor, Spring Boot), web (Kotlin/JS), desktop (Compose for Desktop, JavaFX), and even embedded systems. This flexibility makes KMP a powerful tool for cross-platform development beyond just mobile applications.

Conclusion

Kotlin Multiplatform Mobile (KMM) offers a powerful strategy for sharing business logic between Android and iOS while maintaining native performance and flexibility, critical for performance sensitive applications like premium video streaming.

By centralising logic for content discovery, recommendations, user entitlements, analytics, and caching, KMM helps reduce duplication and streamline development across platforms. However, challenges such as build complexity and limited third-party library support on iOS, especially for advanced video playback or DRM workflows should be carefully considered.

For streaming apps that require custom media players, platform-specific video rendering, or deep OS integrations, a separate platform-specific approach may still be warranted. But for teams aiming to accelerate time to market, reduce code redundancy, and retain native UI experiences, KMM is a strong, forward-looking choice.

Ultimately, aligning your tech stack with your product’s performance, scalability, and maintainability goals is key to building a successful streaming application.

At DIAGNAL, our mission is to deliver awesome experiences for our customers and to continuously develop ourselves. We have a strong commitment to efficiency, trust, and flexibility, and work with major media companies around the world, including Celestial Tiger Entertainment, Intigral, LoungesTV, Optus Sport, WRC Promoter, and more. 

To find out more about how we can help, please reach out to us.