In the battle of cross-platform mobile app frameworks, two players were battling it out for the throne – React Native -for the longest time Vs. Flutter. Over the last decade, a new java-based programming language has gained enough popularity that developers are starting to notice. This new language is Kotlin. There is a new debate that is catching the attention of many developers – Kotlin Vs. Flutter.

Before we start a comparison between Kotlin and Flutter, we need to understand that Kotlin is a programming language and Flutter is a full-stack cross-platform UI toolkit.

Because there are such stark differences in both these mobile app development platforms, we should first understand them individually and then discuss their differences on the following factors:

• Learning Curve
• Performance
• User Experience – UX
• Third-party libraries and Tools Integration
• Scope in Backend Development
• Pricing
• Support for Testing
• Documentation & Community

Kotlin

GitHub Statistics | License – Apache -2.0 | Stars – 35.7k | Fork – 4.4k | Contributors – 475

Kotlin is a general-purpose programming language developed by Jetbrains in 2016. General-purpose means the developers can share code data and business logic with various web programs. Hence Kotlin can interact with XCode and Swift for iOS, Android Studio, and Kotlin for Android. This makes Kotlin a flexible programing language that can interact with different Native environments.

Kotlin is preferred as a general-purpose programming language compared to others because it brings easy solutions to programming misconceptions and errors. Also, the apps built on Kotlin generally observe minimum crashes and downtime.

Kotlin Vs. Java

Kotlin is looked at as a Java alternative. Java is the most known and widely accepted programming language amongst developers. However, ever since Kotlin has stepped into the market, the faith in Java seems to have taken a hit, and developers have started considering Kotlin as a better alternative. Java inspires Kotlin, and it is an improvised version of Java with more beneficial features. The language is clean, minimal, simple, and has fewer rules and formalities than Java. Google also announced Kotlin as an officially supported language to write Android apps in their Google I/O in May 2017. Kotlin Vs. Java is a whole other debate for some other time.

How does Kotlin Multiplatform work?

Kotlin Multiplatform is an additional feature provided by Kotlin for enabling developers to reuse business logic by not imposing any rules on how they want to build their app UI. This ensures that the behaviour, performance, and appearance of the app remain native. Native UI provides the best user experience to customers. Since we compare Kotlin with Flutter, we will see how Kotlin Multiplatform works for two of the best smartphone platforms – Android and iOS.

You start by writing the shared code in Kotlin. For Android – it will get converted to Java bytecode and be executed in the JVM. For Apple, since it doesn’t have a virtual machine, the Kotlin code would be converted to source code (native code for iOS) that goes inside the framework. For converting Kotlin code to source code, you need to use Kotlin Compiler divided into two components –Frontend and Backend. The Frontend part of Kotlin converts the Kotlin Code to IR (Intermediate Representation). The backend converts IR to native code that is machine-executable. This is possible due to the powerful Kotlin/Native Infrastructure built by JetBrains.

Pre-requisites of Kotlin

If you want to learn Kotlin programming language, you should have a basic understanding of –

• Java programming language
• Exposure to any programming environment
• Basic knowledge of basic concepts like – variables, syntax, and commands.

Pros and Cons of Kotlin

When to Use Kotlin?

1. When you want a fast and lightweight application.
2. When the app design needs to be minimal, and the app needs forms and pop-ups to work correctly.
3. When there is no need for a cross-platform environment.
4. The application is a commercial product for the end user.

Popular Mobile Apps based on Kotlin

1. PlanGrid
2. Target
3. SuperAwesome
4. CashApp

Flutter

GitHub Statistics | License – BSD -3 – Clause | Watch – 3.5k | Stars – 114k | Forks – 16.3k | Contributors – 811

Flutter is Google’s open-source and cross-platform UI software development kit. Google introduced Flutter in 2017, and it has been the talk of the town ever since. It helps developers to build unique native-like apps that have cross-platform abilities. It uses Dart as its programming language that makes use of AOT (Ahead-of-Time) compilation.  With Flutter, developers can use a single-code base across various platforms – Mac, Android, iOS, Windows, and Linux.That’s why most tech companies looking to hire expert flutter developer for their app development project.

How does Flutter work?

Flutter is built differently compared to most other frameworks. Flutter framework is composed of widgets. These widgets are rendered on Skia canvas and sent to the platform. The platform shows the canvas and sends the needed events back. The Flutter architecture is divided into three broad categories – Platform, Engine, and Framework. In the platform, Flutter provides a Shell that hosts Dart Virtual Machine. The Shell is platform-specific, giving access to native platform APIs and hosting and establishing control of the platform’s relevant canvas. The next layer is Engine. This layer provides Dart Runtime, Skia Platform Channels, and more. The relevant Flutter engine runs inside the relevant platform Shell. Finally, on top of this, you have Flutter Framework. It is one of the most relevant frameworks for an app developer. It has all the necessary components you would need as a developer to develop your app.

Pre-requisites of Flutter

1. Object Orientated Concepts – Class, Methods, Inheritance, Objects, Abstraction
2. Dart Language
3. Knowledge about Object-Oriented Languages like – C++ and Java

Pros and Cons of Flutter

When To Use Flutter?

1. When you want a full-fledged mobile application.
2. When you want to create an app for retail businesses.
3. When you want to create an app for fintech and banks.
4. When app needs to be made with a tighter deadline and budget restraints.

Popular Mobile Apps based on Flutter

1. Tencent
2. eBay
3. Google
4. Alibaba

The Ultimate Technical Kotlin Vs. Flutter Comparison – 2021

Now that we have a better understanding of both the platforms let us dive straight into the ultimate Kotlin Vs. Flutter comparison and see which one is better suited for your app development needs.

The Popularity and Market Share of Kotlin and Flutter

In terms of popularity, both Kotlin and Flutter are popular with respect to mobile app development. There are plenty of reasons why Flutter why shines, however Kotlin with its own features and functionalities outcome as one of the top mobile app development tool. We’ll discuss the technical terms of each later in this article, but first, we need to focus on the current point ‘popularity and market share of these technologies.

Google Trends Comparision Between Kotlin Vs Flutter

StackOverflow Stats – Kotlin vs Flutter

If we consider StackOverflow, then there are also 55,585 questions tagged with Kotlin versus a whopping 83,484 questions tagged with Flutter.
Here is a StackOverFlow Trend Graph of Flutter and Kotlin

2. Learning Curve of Kotlin Vs Flutter

One of the first things new developers are interested in knowing when deciding on a new framework is the learning curve that comes with it. Overall, Kotlin is easier to learn since Google has many detailed courses available for Kotlin, and it is also interoperable with Java. However, the focus of Kotlin currently is more on its extension –Kotlin Multiplatform. And there is limited documentation and resources available for it in the market compared to Flutter.  Flutter has better comprehensive documentation compared to Kotlin.

Winner for this round of Kotlin Vs. Flutter – Flutter.

2. Kotlin Vs Flutter Performance

Performance is an important factor to consider in the debate of Kotlin Vs. Flutter. When we discuss performance, Flutter gains points for Hot Reload and Hot Restart feature, allowing developers to change their codes and see its effect instantly, which speeds up the development process, making it easier to build apps. Kotlin has a different approach and provides more native features and components like Bluetooth, a Camera, and more.

Winner for this round of Kotlin Vs. Flutter – Draw.

3. User Experience – UX perspective of Kotlin Vs Flutter

Flutter is a widget-oriented cross-platform framework. It has unparalleled customization options, allowing Flutter developers to create unique, functional, and scalable applications. Kotlin is a general-purpose language that makes it cross-platform capable. Using this language, Kotlin developers can easily create efficient applications without any issues.

Winner for this round of Kotlin Vs. Flutter – Draw.

4. Third-party libraries and Tools Integration

Flutter is an open-source, cross-platform SDK. It provides easy integration of third-party UI development tools. Kotlin is a programming language that is capable of developing native-like cross-platform apps. For this, it makes use of native tools like SwiftUI and Jetpack Compose.

Winner for this round of Kotlin Vs. Flutter – Kotlin.

5. Scope in Backend Development

Google backs Flutter; hence it lets Flutter developers leverage Firebase (Backend-as-a-service platform) to write codes at the backend. Kotlin multiplatform allows developers to directly write the backend code without any hassle.

Winner for this round of Kotlin Vs. Flutter – Kotlin.

6. Pricing

We are comparing pricing in regards to the app development costs with Kotlin and Flutter framework. Both Kotlin and Flutter are open-source and free to make use of platforms. Flutter provides the fastest way to build an MVP – Minimal Viable Product. Moreover, it significantly reduces app development cost and time as you can make Android and iOS apps using a single codebase at the same time with Flutter. Since Kotlin is also open-source, you can directly download it from Github and start using it.

Winner for this round of Kotlin Vs. Flutter – Draw.

Also Check our Article : Top 8 Hidden Cost of App Development

7. Support for Testing

Flutter has immense testing support for various features to test widgets, conduct unit testing, and app integration. Flutter’s well-documented support also is a plus point. Flutter also works on Firebase, which is an efficient backend-as-a-service tool. Flutter can integrate quickly with iOS and Android platforms, which makes the testing process easier. However, with Kotlin, you don’t need to integrate. Kotlin is multiplatform which enables developers to work using their native framework. This helps developers work with their native tools for cross-platform apps too.

Winner for this round of Kotlin Vs. Flutter – Kotlin.

8. Documentation and Community

Flutter is relatively new and rising as a platform. It has one of the most impressive and extensive documentation amongst all popular frameworks for a relatively newer framework. Kotlin has decent documentation ready and is constantly working on improvising it for its developers. As far as community goes, Flutter already has 811 contributors even after being a new platform compared to Kotlin that has 475 contributors on GitHub.

Winner for this round of Kotlin Vs. Flutter – Flutter.

9. Job Opportunity

Last but certainly not least, when comparing Kotlin and Flutter, we need to consider Job and Market Share of these two mobile app development frameworks. As a fresher who is looking to learn either one of the frameworks for career purpose or as a company that is trying to decide between the two frameworks, market share and job opportunity can be important metrics to consider. Here are the overall market stats gave by App Brain on both these mobile app development frameworks –

Kotlin Vs. Flutter Comparison Table

To Conclude
As we can see above, Kotlin and Flutter are both capable platforms for developing efficient cross-platform apps. They both bring different advantages and limitations to the market. And since Kotlin is a programming language, we cannot directly declare a winner in the hot debate of Kotlin Vs. Flutter. It is anyway more beneficial for a developer to have a clearer idea of which tool to use for their requirements.

When to Use Kotlin?

Kotlin is an ideal programming language for revamping your existing application. It is 100% interoperable with Java and simplifies the app editing process significantly. Kotlin also makes writing highly sophisticated and heavy codes easier. Its fail fast compiler detects bugs automatically and resolves them instantly.

When to Use Flutter?

Flutter is mostly famous for its unparalleled hot-reload feature. Using this, a developer can instantly check the changes they make to the source code. Flutter is ideal for making an MVP product or prototype to show it to your potential investors.