Migrate Android app to Kotlin Multiplatform: A guide for 2026

TL;DR

Migrating an Android app to Kotlin Multiplatform (KMP) can be done incrementally.
Start by sharing the networking, data, and domain logic layers.
Use tools like Kotlin 2.1+, Ktor, and SQLDelight for a smooth transition.

What is Kotlin Multiplatform and why migrate?

Kotlin Multiplatform (KMP) allows developers to share code across different platforms, notably Android and iOS. Migrating your existing Android app to KMP lets you leverage shared business logic while maintaining platform-specific user interfaces. This approach can significantly reduce development time and effort, enabling faster updates and feature releases.

What parts of an Android app should you share first?

The first layers to migrate are the networking, data, and domain logic components of your app. These layers typically account for about 70% of your codebase, making them prime candidates for sharing. By focusing on these foundational layers, you can create a robust shared module that can be utilized by both your Android and iOS applications.

Migration priority matrix

Layer	Estimated Effort	Recommended Order
Networking	Low	1st
Data	Medium	2nd
Domain Logic	Medium	3rd
UI	High	4th
Platform-Specific	Varies	Last

How do you keep the existing Android UI while adding iOS?

You can keep your existing Android UI intact while creating a separate shared module for your business logic. This allows you to gradually develop the iOS UI without disrupting the Android experience. By using the expect/actual mechanism in Kotlin, you can define platform-specific implementations while sharing the core logic across platforms.

What is the incremental migration strategy?

The incremental migration strategy involves transitioning your app in stages, starting with a shared module and progressively migrating screens. This method allows you to minimize risks and maintain functionality throughout the migration process. A typical timeline for such migrations can range from 3 to 6 months, depending on the size of your app and the complexity of the code.

Step-by-step migration checklist

Establish a shared module: Create a new KMP project and set up a shared module for your networking and data layers.
Implement shared code: Use Ktor for networking and SQLDelight for data management.
Migrate domain logic: Move your business logic to the shared module.
Add iOS targets: Set up an iOS target in your KMP project.
Maintain Android UI: Keep your existing Android UI while developing the iOS UI separately.
Test thoroughly: Use unit tests to ensure shared code works seamlessly across platforms.
Iterate and improve: Continue refining the shared module and expand your migration to more screens.

What are common pitfalls during migration?

One common pitfall is introducing platform-specific dependencies into your shared code, which can lead to complications. Ensure that any libraries you use are compatible with both Android and iOS. Additionally, avoid large-scale migrations all at once; instead, adopt an incremental approach to keep your application functional throughout the transition.

How does KMPShip assist in migration?

KMPShip provides a clean architecture reference for structuring your shared versus platform code. By following their guidelines, you can ensure a well-organized project that adheres to best practices for Kotlin Multiplatform development. This will help you maintain a clear separation between shared and platform-specific logic, making your migration smoother.

Frequently Asked Questions

What is the best way to start migrating an Android app to KMP?

The best way to start migrating is by creating a shared module that includes your networking and data layers. Focus on these areas first, as they contain the bulk of your app’s logic, allowing for a smoother transition.

How long does it typically take to migrate an Android app to Kotlin Multiplatform?

The migration timeline can vary widely, but most developers report a typical timeframe of 3 to 6 months, depending on the complexity and size of the app. The more incremental your approach, the easier it will be to manage.

Can I use existing libraries with Kotlin Multiplatform?

Yes, you can use existing libraries, but be cautious of platform-specific dependencies. Libraries like Ktor for networking and SQLDelight for database access are designed to work seamlessly with Kotlin Multiplatform.

Why is incremental migration preferred?

Incremental migration is preferred because it allows you to maintain functionality throughout the process. It reduces the risk of introducing bugs and provides opportunities for testing and validation at each stage of the migration.

What tools are essential for migrating to KMP?

Essential tools for migrating to KMP include Kotlin version 2.1 or higher, Android Studio for development, Ktor for networking, and SQLDelight for database management. These tools streamline the migration process and enhance your development efficiency.