What is Kotlin Multiplatform? Pros and Cons of KMP in Mobile App Development

If you’ve read a bit about mobile app development, you probably know that native apps often ensure the best performance but it requires writing code for iOS and Android separately. Flutter, on the other hand, offers budget savings and faster time to market, but its apps lack native experience.

What if I told you that there’s a third option worth consideration? Kotlin Multiplatform gives the app the native touch and doesn’t require writing the entire code twice for Android and iOS.

Get to know Kotlin Multiplatform and find out when it’s a good alternative for Flutter and native code.

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Key takeaways

• Kotlin Multiplatform (KMP) is an open-source SDK that allows sharing code between platforms, saving time and money in the development process.
• KMP supports mobile, web, and desktop app development, with the Compose Multiplatform framework enabling UI sharing.
• While still a young technology, KMP offers several advantages over fully native code, including faster app development, time and budget savings, and a native look. It is also easy to learn for Android developers.
• KMP ensures consistent architecture and features across all platforms, providing a seamless user experience.
• When comparing Kotlin Multiplatform to Flutter, KMP offers facilitated implementation with native code and access to native libraries, although Flutter has more custom libraries and tools.

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What is Kotlin Multiplatform?

Kotlin Multiplatform (KMP) is an open-source SDK that combines the benefits of native and cross-platform app development. It enables sharing parts of code between many platforms.

As a result, there’s no need to build every element of the Android and iOS apps separately, so you save time and money.

As the name suggests, the Kotlin programming language is essential to this technology. Common code in Kotlin compiles into native code for Android, iOS, desktop, and web systems. It allows sharing an entire business logic or part of it, using APIs dedicated to specific platforms and easily accessing native features.

Currently, with KMP, you can develop the following:

• Mobile apps (Android, iOS)
• Web apps
• Desktop apps (macOS, Windows, Linux)

Compose Multiplatform

With the Compose Multiplatform framework, you can also share the UI implementations, although it currently only supports Android and desktop apps.

The possibilities of Compose Multiplatform are constantly growing, though. Soon, it will support even iOS and web apps, which should significantly speed up the app development process.

Kotlin Multiplatform is still a young technology. JetBrains, a company that developed it, released a stable version of KMP in November 2023, although this project was announced back in 2017. No wonder that some elements still need improvements, especially regarding sharing UI.

Benefits of choosing KMP over fully native code

Faster app development

KMP shortens time-to-market because building apps for two platforms takes less time, thanks to sharable parts of code. Software developers can choose app elements they want to share between Android and iOS. Some parts can be written with KMP, and others in platform-specific code.

Time and budget savings

Completing the KMP project takes less time than building two native apps entirely separately. The development process ends earlier, which saves money.

Native look

Kotlin is a language that compiles into native code, ensuring fast performance. Although KMP is based on a language mainly used for building Android apps, it can be combined with Compose UI and SwiftUI, which provides better UX for iPhone users.

Easy-to-learn for Android developers

KMP relies on Kotlin, a language well-known to Android developers, so they don’t need to learn a new one to take advantage of Kotlin Multiplatform.

Scalable growth

Many product owners decide to move to KMP even though they already have existing native apps. Why? App development with shared business logic is faster, and KMP makes code sharing easily scalable. You can gradually move native code to Kotlin Multiplatform, starting from the most essential features. As a result, the migration process doesn’t significantly slow down app development.

Consistent architecture and features across all platforms

Shared logic enables the creation of the architecture only once on both platforms. It also applies to features. This way, they work in the same way. So, when users move from iPhone to Android, the only difference they see is in the UI, as both apps ensure the native experience.

Kotlin Multiplatform vs Flutter – what should you choose?

You may wonder what the difference between Flutter and KMP is if they both enable code sharing between multiple platforms. The two of them can also be combined with native code.

You should know that these solutions offer unique benefits but also limitations. Knowledge about them is essential when selecting the technology for your mobile app project.

Pros of Kotlin Multiplatform

Facilitated implementation with native code

Some apps must have many features that connect with native elements, such as the camera or NFC payments. Although you can build them in Flutter, if the app has a lot of such features, it should be faster in KMP.

Access to native libraries

There aren’t as many custom libraries and tools compatible with KMP as there are with Flutter. However, with KMP technology, it’s possible to use native libraries, so it’s easier to develop custom elements. Hopefully, as Kotlin Multiplatform grows, the number of accessible libraries and APIs should grow.

Easier to find Kotlin experts than Dart

KMP relies on a popular language used in Android app development. Finding a Kotlin developer who has learned how to use Kotlin Multiplatform isn’t so hard. Flutter, on the other hand, uses the far less well-known programming language called Dart. There aren’t as many specialists with experience in Dart, so recruiting one can take longer.

Pros of Flutter

Faster UI development and time-to-market

In Kotlin Multiplatform, UI rendering isn’t shared between Android and iOS platforms, so developers must handle it separately.

Flutter, however, allows them to develop UI once for both operating systems. Of course, it doesn’t provide a fully native experience, but the UI design is consistent across two systems. Thus, Flutter ensures faster time to market and allows you to save some budget on UI development.

More compatible tools, packages, widgets, and libraries

Flutter is an older and more mature technology with more dedicated libraries and tools to choose from. They make it easier and faster to build apps, so the development cost is smaller.

KMP’s libraries aren’t so well-developed yet, even though Kotlin Multiplatform technology also offers some promising solutions. However, they mostly allow us to build elements of the app that are related to app logic, such as logging, testing, local data storage management, or networking.

Hot reload enables instant change testing

When software developers make a change in Flutter code, they can immediately see how it affects the app. This is possible thanks to a hot reload feature.

It speeds up the app development process because a person who writes code can quickly check if it works as intended. Kotlin Multiplatform does not offer a similar option.

Big community ensures fast growth

In 2023, Flutter took the second place in the overview of the fastest-growing technology skills, according to Statista. The number of developers who improve and optimize Flutter’s performance is rapidly growing. As a result, it constantly offers new opportunities.

Examples of Kotlin Multiplatform apps

The theory sounds promising, but how do Kotlin Multiplatform apps actually work? Below, we present a few examples of apps developed with this technology.

McDonald’s Global Mobile App

The team of McDonald’s Global Mobile App chose Kotlin Multiplatform to save time on writing business logic. With this cross-platform technology, they only have to write it once for both systems. They also wanted a native UI to ensure the best possible performance.

Read more about this project on Medium.

Source: Apple App Store

Memrise App

You probably know this app for learning languages. Memrise also uses Kotlin Multiplatform because it allows the sharing of business logic across Android and iOS mobile platforms. Before, they had to write the same code in Kotlin and Swift, so KMP was a time-efficient solution.

Read more about their approach on Medium.

Source: Apple App Store

Quizlet App

The purpose of Quizlet is to facilitate learning. The team decided to try cross-platform development because they wanted to reduce the time required to write code on two platforms. As they say, Kotlin Multiplatform solved their previous performance problems and made the app less prone to errors.

Get to know the details from their blog post.

Source: Apple App Store

9GAG App

After trying native programming, React Native, and Flutter, the 9GAG team finally chose Kotlin Multiplatform. It helps them work faster, so users can enjoy new features earlier. On top of that, KMP ensures the same experience on both iOS and Android.

Find more info about this project on Medium.

Source: Apple App Store

Final thoughts on KMP in mobile app development

Kotlin Multiplatform is a cross-platform option worth consideration when you want to develop app for two mobile operating systems, ensure the best UX for Android and iOS users, and save time and money without hurting the performance.

If you want to know which technology is better in case of your app – Kotlin Multiplatform, Flutter, or native code – send us a message. Our team can analyze your project and explain to you pros and cons of available solutions.