KMP or Flutter - what should startups choose for their app development?

Startups often operate in rapid environments where speed is critical. A good cross-platform framework enables rapid development by allowing a single codebase to be used across multiple platforms, which reduces development time. It also means that fewer developers are needed, which consequently reduces development costs as well. React Native used to be a popular choice with its JavaScript-based approach, but lately, more and more people are opting for new choices like Flutter, and especially Kotlin Multiplatform which gained the ability to compete with cross-platform technologies that are far more established and older.

Why does Netflix use Kotlin Multiplatform?

Kotlin Multiplatform (KMP), developed by JetBrains, is a capability within the Kotlin programming language that allows developers to write shared code for multiple platforms, such as Android, iOS, web, and desktop while enabling platform-specific implementations where necessary. It means that KMP, depending on the implementation, can share part of the logic, the entire business logic, or both the logic and UI.

KMP advantages

1. Independent integration: Kotlin is an SDK rather than a framework. What does it mean? Businesses with apps can easily evaluate their potential by adding a module or migrating a few features. This significantly helps Kotlin in addressing the main obstacle to switching to a new codebase.
2. Cost-effectiveness: It reduces the time required to build apps by minimizing the need for separate iOS/Android development teams, thus lowering development and maintenance costs.
3. Native performance: KMP allows direct access to native APIs and libraries. It means developers can implement custom features that are unique to each platform. That way KMP takes advantage of the latest platform-specific functionalities and provides a rich user experience.
4. Separate UI development: Developers can use platform-specific UI components and provide tailored functionalities for iOS and Android. By creating separate UI for each platform, users get that “native feeling, " meaning they have intuitive and familiar behavior since some things work differently for iOS and Android.

KMP challenges

1. Investment in adopting KMP: Developers who are not already familiar with Kotlin or multi-platform development concepts need to understand how to effectively share code across platforms. However, the growing community and extensive documentation are valuable resources that can help ease this transition.
2. Development time: Developers need to implement separate UI, and that can lead to increased development time and effort for creating and maintaining multiple user interface codebases. Still, it is a faster option than not sharing a business logic.
3. New and still maturing: Compared to some other frameworks, this implies less prepared libraries and plugins, but it also offers an ideal opportunity to grow on a cutting-edge technology that is quickly gaining popularity and support.

Having considered all the pros and cons, Netflix decided to use Kotlin Multiplatform for its studio applications, enabling the team to share business logic across platforms while maintaining native user interfaces and performance. With a shared codebase, Netflix develops features once and deploys them across multiple platforms, speeding up the development process.

What is Flutter?

Flutter, created by Google, is an open-source UI toolkit that enables developers to build natively compiled applications for mobile, web, and desktop from a single codebase using the Dart programming language.

Flutter advantages

Hot reload: This allows developers to instantly view changes without restarting the app, which speeds up the development process.

UI/UX capabilities: Flutter has a rich set of customizable widgets, which allow developers to create highly flexible and visually appealing user interfaces that provide a consistent experience across all platforms.

Single codebase: Developers write code once and deploy it on multiple platforms such as iOS, Android, web, and desktop. It means there is a code that covers both business logic and UI. This approach significantly reduces development time, effort, and costs.

Strong community and support: The developer community around Flutter is big, matching the size and activity of communities behind other well-known frameworks such as React Native. With frequent updates, bug updates, and the launch of new features, this vibrant community helps Flutter evolve quickly.

Flutter challenges

Large app size: Flutter includes its own set of UI components which makes the app size larger than the native ones. Kotlin Multiplatform and React Native tend to have smaller app sizes since they support native components provided by the platform.

New language: Dart is a completely new language used for Flutter and it may bring challenges compared to more established languages like JavaScript or Python. Developers may find fewer resources which makes it harder to find solutions.

Limited Native flexibility: In case developers need highly tailored or platform-specific features that aren't easily found in the Flutter community, they might have to rely on third-party plugins or write platform-specific code, which might complicate the development process.

So, what is the best choice to make?

The best option depends on your app’s needs, as well as the time and budget available.

For startups looking to build an app efficiently and affordably, Kotlin Multiplatform (KMP) is usually a good solution. KMP lets you use the same code across different platforms while still getting the fast, smooth performance you expect from each device. It's perfect if you already know Kotlin because it cuts down on learning time and speeds up how quickly you can launch your app.

On the other hand, Flutter is an option if your app doesn’t require a lot of platform-specific code. Therefore, it allows you to quickly launch your app by having a single codebase across multiple platforms like iOS, Android, web, and desktop.

Of course, keep in mind that using Flutter doesn’t mean you can’t have a native feel, or that you can’t quickly launch your app with KMP. It is just that KMP requires separate designs for iOS and Android, but that ensures your app feels just right on each type of phone.