Flutter vs Kotlin Multiplatform: The 2024 Guide

Write your code once and deploy it everywhere. Sounds great, right? Well, here's the thing about cross-platform mobile development: everyone wants it to be easier.

Enter Flutter and Kotlin Multiplatform, two contenders in the "write once, run anywhere" arena.

Flutter, backed by Google, is the flashy newcomer with its own language (Dart) and a "everything is a widget" philosophy. Kotlin Multiplatform, on the other hand, is like that friend who always brought great snacks to movie night and has now decided to host the whole party – familiar and reliable, but suddenly aiming to do a lot more.

Is it worth it to learn Dart for Flutter, or should you stick with Kotlin?

Let's break down these two contenders and see if one is actually better than the other.

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The table below highlights the quick differences between Flutter vs Kotlin Multiplatform.

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What is Flutter?

Flutter is a reactive cross-platform mobile development framework created by Google and uses Google’s Dart language. Flutter was initially unveiled at the 2015 Dart developer summit. Three years later, Google released the first stable release version — Flutter 1.0 — on December 5, 2018,  at the Flutter Live event. It is used to develop applications for Android, iOS, Windows, Mac, Linux, Google Fuchsia, and the web using a single code base. Google’s strong support helped Flutter quickly overtake other cross-platform options like React Native. At its core Flutter is a reactive framework that comes with a large number of ready-to-use widgets. Flutter’s applications are compiled using arm C/C++ library so that it’s closer to machine language and gives a near-native performance.

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Flutter pros

Some of the advantages of cross-platform mobile app development using Flutter include:

• Hot Reload: One of the biggest pros of using Flutter is the ability to get a near-instant reflection of changes. Hot Reload allows developers to make changes to the codebase and not have to restart the application to see the change reflected.
• Cross-platform development from one codebase: With Flutter, writing one codebase can support iOS and Android platforms. The same codebase can also be used for the other platforms supported by Flutter including the web. And with Flutter having its widgets and designs you have the option to create the exact same app on both platforms. Or have them vary if you wish.
• Cut down on debugging time: Having the same exact app for both platforms and the same codebase means that you will only need to debug once instead of separately for each platform.
• Fast fluid UI: Flutter apps boast a fluid and fast UI and this is thanks to the Skia Graphics Library. With the library, the UI is redrawn each time when a view changes. With help from the GPU, this helps Flutter UI deliver a smooth and fast experience.
• Great app design: Flutter has its own custom widgets and doesn’t use native system components. Flutter also has a very user-friendly UI. This distinct yet very attractive look gives Flutter a big advantage over React Native.
• Same app UI, even on older devices: The non-reliance on native components and having cross platforms be the exact same also works for older vs newer devices. Apps will look the same whether on older iOS/Android devices or newer versions.
• Perfect for MVPs: A huge factor when looking for cross-platform development options is how quickly and easily it can build an app. There is a huge demand for building an MVP (Minimum Viable Product) for an app and Flutter is the best option to accomplish this.
• Flutter community and support: Traditionally due to Flutter being a newer option than React Native, community support has always been a disadvantage when compared. But due to its surging popularity Flutter has surpassed React Native in popularity and community support. Flutter currently has 158,000+ stars on Github while React Native has 113,00+ stars. Google has also continued to strongly support Flutter and its development and now it is a very stable and mature option.
• Open source and completely free: Flutter is completely free to use, as opposed to other options like using an app builder or no-code solutions for your cross-development needs.‍

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Flutter cons

While Flutter is surging in popularity amongst the cross-platform development tools out there at the moment, it is certainly not perfect. Some of the disadvantages of Flutter include:

• Dart language: While the Dart language itself is a very strong programming language, it was only developed alongside Flutter. In order to develop apps on Flutter, you will need to specifically learn how to use and write Dart. This barrier for entry can be discouraging to many users who prefer to easily adapt to a common language such as Javascript as is the case with React Native.‍
• Libraries compared to native development: Libraries have come a long way but there is still some functionality that would otherwise be available or better implemented in native development thanks to the variety of libraries.‍
• App sizes: Although Flutter has been working on this and they have their own guide to reducing file sizes, Flutter apps tend to be a larger size than native ones.

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Check out our essential list of Flutter resources and development tools.

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What is Kotlin Multiplatform?

At first glance, comparing Kotlin and Flutter might raise some eyebrows due to Kotlin being traditionally known as a programming language. However, JetBrains  released Kotlin Multiplatform in 2020 as an additional feature of the language that helps it expand beyond Android app development. Kotlin Multiplatform lets developers use a single codebase to develop apps for both iOS and Android.

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Kotlin Multiplatform pros

• Modular integration: Probably the biggest benefit in favor of Kotlin is that it’s an SDK and not a framework. This means that teams with existing apps can simply add a module or migrate a small part to assess its viability without a huge commitment. This really helps Kotlin address the biggest deterrent when moving to a new codebase.‍
• Easy to learn: Kotlin as a programming language is very popular already and its syntax is very similar to other popular languages such as Swift and Java. This also helps reduce the barrier for entry and encourages developers to pick up Kotlin as an alternative.‍
• A single codebase for the business logic: Cross-platform development solutions by definition let you use a single code base for various platforms and Kotlin Multiplatform is no different. The advantage of Kotlin is that it lets you share logic and libraries below the UI layer. This enables developers to directly interact with their native environment (iOS/Android).‍
• Native UI experience: Kotlin Multiplatform unlike Flutter does not demand developers to follow its own UI. It lets you utilize native UI elements to its fullest as if you are developing natively.‍
• Native performance: This utilization of native components helps Kotlin developed apps perform as efficiently as they would as natively developed apps. This is a much sought-after advantage for various developers looking to make something beyond an MVP.

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Kotlin Multiplatform cons

• Fresh out of beta: Kotlin Multiplatform was introduced in Kotlin 1.2 and as of Kotlin's 1.9.20 release in November 2023, the SDK is out of beta and production ready. However, this is only true for the core parts of Kotlin Multiplatform and many advanced parts are still in beta. It has surprising adoption in big products(VMware, 9GAG, McDonald's, CashApp, Netflix, and Baidu), but companies will want to hold off on using advanced features that are not production ready‍
• Community support and libraries: Being a relatively new alternative, libraries and community support is somewhat limited. However, it's worth mentioning that they have been rapidly growing over the past few years and show no sign of slowing.‍
• Not a closed solution: Kotlin Multiplatform still needs mobile teams to be at least familiar with the different tech stacks. Utilizing a lot of native components means that it won't be sufficient to be familiar with only Kotlin on its own. This isn’t the case with Flutter where you can do everything purely using Flutter.‍
• Takes more development resources: When compared with Flutter, Kotlin isn’t the best solution to create an MVP or prototype as fast as possible. Its need for various semi-native components increases the cost of development both in terms of time and resources.

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Who wins?

Over Kotlin Multiplatform's relatively short life, it has become a serious contender among cross-platform solutions. Ultimately, the choice between Flutter and Kotlin Multiplatform will depend on your app's needs.

Teams that are developing an MVP app or need to prioritize development and iteration speed over native performance and are able to pick up Dart quickly might be better off with Flutter. If your team prioritizes native performance and UI, or you don't want to invest in learning a new language, Kotlin Multiplatform could be the technology for you.

It is worth noting that this verdict is a huge testament to Kotlin Multiplatform and the team at JetBrains. Kotlin Multiplatform has come a very long way over the course of just four years, becoming a serious contender to much older and more mature cross-platform technologies.