For most teams starting a new app from zero, Flutter is the faster and cheaper way to ship on iOS and Android. In the Kotlin Multiplatform vs Flutter decision, KMP wins when you already have native apps or a strong Kotlin team. It lets you share business logic while each platform keeps its own native UI.

This post compares both stacks on six factors a CTO pays for. It also covers the two myths worth dropping and the mistake we see most. It ends with how we make the call for clients.

How the two stacks actually differ

Flutter draws every pixel itself. You write UI and logic once in Dart, and the Flutter engine renders that UI on its own canvas on each platform. Native features such as Bluetooth or HealthKit come in through plugins or platform channels.

Kotlin Multiplatform shares code, not necessarily UI. You write networking, storage, validation and business rules once in Kotlin. That code compiles to a library on Android and to a native framework on iOS.

The UI can stay in Jetpack Compose and SwiftUI. Or you can share it too with Compose Multiplatform, which reached stable for iOS in 2025.

That difference drives everything below. Flutter asks how much of your app is UI. KMP asks how much of your app is logic that must behave the same on both platforms.

A short conversation often settles this faster than a month of research, so book a 30-minute discovery call and get a straight recommendation for your team and roadmap.

Kotlin Multiplatform vs Flutter, factor by factor

Performance

Both produce native machine code in release builds. Flutter compiles Dart ahead of time. KMP runs on the JVM-based Android runtime and compiles to native binaries on iOS through Kotlin/Native.

For typical business apps, users will not notice a difference. That covers forms, lists, feeds and checkout flows. The differences show up at the edges.

  • Flutter adds its engine to your binary, typically a few megabytes. It renders with its own engine, now Impeller (see the Flutter documentation). Text input, scrolling physics and accessibility are Flutter's re-creations of platform behaviour, and they are very close but not identical.
  • KMP with native UI has no rendering layer of its own. Scrolling, text input and accessibility behave exactly like the platform, because they are the platform. The trade-off is Kotlin/Native's garbage collector on iOS. Allocation-heavy shared code can run slower than the same code in Swift, so profile hot paths early.

Developer availability

Flutter developers are now a recognised hiring category. One Flutter developer can cover both platforms. Dart is rarely anyone's first language, but strong developers pick it up in a few weeks.

Almost every Android developer already writes Kotlin, so the KMP shared layer feels familiar to them. The gap is on iOS. Your Swift developers must use a Kotlin-generated framework, and few of them have done it before.

Engineers who have led a KMP project in production are still scarce. Expect a longer search for that role than for a senior Flutter developer.

Cost

Flutter typically shares most of the codebase, often well over 80%, because UI and logic live in one place. KMP with native UI typically shares 40 to 70%, since you still build each screen twice. The exact split depends on how screen-heavy your app is.

As a rough guide, compare each against building two separate native apps:

  • Flutter typically cuts build cost by 30 to 40%.
  • KMP with native UI typically cuts it by 15 to 30%.
  • KMP with Compose Multiplatform lands closer to Flutter on cost. You also take on Flutter-like trade-offs, because the UI is no longer the platform's own.

Time to market

Flutter is usually faster for a new product. Hot reload, one UI and one team typically save weeks on an MVP. KMP's first-time setup takes longer: Gradle configuration, iOS framework integration and macOS CI runners often take one to two weeks.

The picture flips for existing apps. With KMP you can move one module at a time, such as networking or the pricing engine, while both apps keep shipping. Adopting Flutter in an existing native app is possible with add-to-app, but it is rarely the cheaper route.

Ecosystem maturity

Flutter has been stable since 2018. Its package registry, pub.dev, is large, but plugin quality varies. Before you depend on a plugin, check its last release date and open issues.

KMP has been stable since November 2023. Google officially supports it for sharing business logic between Android and iOS, as outlined in the Android developer documentation. The core libraries are solid: Ktor for networking, SQLDelight or Room for storage, kotlinx.serialization and Koin.

KMP has fewer ready-made packages. You lose less than it sounds, because platform code can always call native SDKs directly with no plugin layer.

Long-term maintenance

With Flutter, you maintain one upgrade path: Flutter SDK, Dart and plugins. The risk comes when Apple or Google change their design language, as Apple did with Liquid Glass (see the Human Interface Guidelines). Flutter has to reimplement those widgets, and you wait or build them yourself.

With native UI on KMP, you get new platform UI as soon as the OS ships it. The maintenance cost moves elsewhere: Kotlin, Gradle and Xcode upgrades must stay compatible. Swift interop also goes through Objective-C headers, which makes coroutines and sealed classes awkward. Tools such as SKIE improve this a lot.

Which stack to choose

Choose Flutter if

  • You are building a new product with no native code worth keeping.
  • Your UI is heavily branded and should look identical on iOS and Android.
  • You have a small team, typically two to four developers, and need both stores within about four months.

Choose Kotlin Multiplatform if

  • You already have native apps and want to stop writing the same logic twice without a rewrite.
  • Your app relies on deep platform features such as home-screen widgets, watch apps, CarPlay, HealthKit or background Bluetooth.
  • Your team is strong in Kotlin, ideally on the backend too, so validation and models can be shared with the server.

Two myths that are now out of date

"Flutter apps stutter on first run"

This was true. Early Flutter compiled shaders while the app ran, which caused visible jank the first time an animation played. Impeller precompiles its shaders and is now the default on iOS and modern Android. When we see jank in a Flutter app today, the cause is almost always the app's own code, such as rebuilding large widget trees.

"Kotlin Multiplatform is experimental"

That label is about two years out of date. KMP went stable in November 2023, and Google followed with official support in 2024. The remaining rough edges are mostly in Swift interop and tooling, not in the core compiler.

The mistake teams make most often

Teams choose on the demo instead of the org chart. A prototype shows which stack is quickest in week one. It says nothing about who will own the code in year three.

The classic version is choosing KMP without buy-in from the iOS developers. They treat the shared framework as a black box, wrap it, and slowly rewrite the logic in Swift. You end up paying for shared code and duplicated code at the same time.

The reverse also happens. A team of experienced native specialists gets told to ship in Flutter, and they spend months fighting the framework. Ask who will maintain the app, then pick the stack they will defend.

How we decide this for clients

We build in both stacks, so we have no reason to push either one. The decision usually takes one or two working sessions plus a short spike.

  1. Map the team. We look at who writes code today and who will maintain it in three years, including any planned hires.
  2. List platform-specific features. If more than about a quarter of the roadmap depends on deep native APIs, we lean towards KMP.
  3. Estimate the UI-to-logic split. Screen-heavy apps with thin logic favour Flutter. Rule-heavy apps such as pricing, compliance or offline sync favour KMP.
  4. Run a one- to two-week spike. We build the hardest screen and the riskiest integration in the leading option, then measure it.
  5. Write the decision down. We record the reasons and the conditions that would reverse them, so the next CTO understands the choice.

FAQ

Is Kotlin Multiplatform better than Flutter?

Neither is better in general. Flutter is usually faster and cheaper for new apps with a single small team. KMP is better when you have existing native apps, need native UI, or already have a strong Kotlin team.

Can Kotlin Multiplatform share UI like Flutter does?

Yes, through Compose Multiplatform, which became stable for iOS in 2025. You then share most of the app, much like Flutter. You also accept that the iOS UI is no longer built with SwiftUI or UIKit.

Will Google drop Flutter in favour of Kotlin Multiplatform?

Google has made no such announcement and continues to release Flutter on a regular schedule. It supports KMP for sharing logic between native Android and iOS apps, which is a different job. Choose based on your team and product, not on rumours about either project's future.