Kotlin Multiplatform vs Flutter: A Simple Comparison for Android Developers

# Kotlin Multiplatform vs Flutter: A Simple Comparison for Android Developers

As an Android developer, you've probably heard of Kotlin Multiplatform (KMP) and Flutter as options for building cross-platform apps. Both aim to help us write code once and run it on both Android and iOS — but they go about it in very different ways.

If you're wondering which one might be a better fit for your next project, here's a simple breakdown of the core differences between them, with a focus on what makes sense for us Android folks.

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## 🌱 1. Language and Ecosystem

Kotlin Multiplatform (KMP):
You use Kotlin — the same language you already love and use daily. KMP lets you share code (like business logic, networking, and data layers) between Android and iOS, but keeps the UI platform-specific.
➕ Big win: You don't need to leave the Android/Kotlin ecosystem.
➖ You still have to write native UI for iOS (Swift/SwiftUI), which means knowing or learning some iOS development.

Flutter:
Uses Dart, which is a different language from what most Android devs are used to. Flutter is all about writing everything (UI + logic) in one codebase.
➕ The UI looks and behaves the same on both platforms.
➖ You'll be working outside the traditional Android view system (no XML, no Jetpack Compose).

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## 🧱 2. UI Development

KMP:
No shared UI. You build UI separately for Android (in Jetpack Compose or XML) and iOS (in SwiftUI/UIKit).
➕ Native look and feel, best performance.
➖ Double the work on the UI layer.

Flutter:
UI is built with Flutter widgets, which are rendered using Flutter's own engine.
➕ Fast development with hot reload, lots of pre-built widgets.
➖ Not native — can feel a bit off if not styled carefully.

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## 🔄 3. Interoperability

KMP:
Great interop with Android because it's Kotlin. iOS interop is also strong thanks to the Kotlin/Native compiler, but needs some setup.
➕ On Android, it feels just like writing normal code.
➖ On iOS, there's a learning curve around how shared code maps to Swift.

Flutter:
Talks to native code using "platform channels". You can use Kotlin/Swift to write platform-specific code when needed.
➕ One codebase.
➖ Interop requires writing boilerplate for communication between Dart and platform code.

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## 🚀 4. Tooling and Performance

KMP:
Uses Android Studio/IntelliJ and Xcode for respective platforms.
Performance is native since you're using platform-native code.
➕ Best for apps where performance matters, like real-time features or hardware interactions.

Flutter:
Excellent tooling (DevTools, hot reload, UI inspector).
Performance is usually very good, but not "true native".
➕ Best for fast prototyping, design-heavy apps.

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## 🎯 Final Thoughts

If you're an Android developer:

- Choose KMP if you want to stay in the Kotlin world, keep using Android's native tools, and are okay writing some Swift for iOS UI. It's a great choice for teams who already have Android and iOS devs and want to unify business logic.

- Choose Flutter if you want to write everything once, including UI, and are okay stepping outside of the native Android ecosystem. Flutter shines for startups, design-focused apps, or when you're working solo.

Both are powerful — it just depends on what kind of app you're building and how much native control you need.

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💬 _Have you tried KMP or Flutter yet? I'd love to hear your experience — especially from other Android developers navigating this choice!_

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This post is part of my series on mobile development technologies. Check out my other posts on Android development, team building, and career growth.