Cross-platform development is on the upswing, and you may wonder why. Briefly, it allows running applications on multiple platforms – be it iOS or Android – and supports businesses to reach more customers, therefore, earning more money. Hence, there always exists a tug of war between the best cross-platform applications. Therefore, let us look at a similar tug of war, Flutter vs Kotlin, and draw a conclusion on which is the perfect one for 2021.

What is Cross-platform development?

Cross-platform development is the method of developing software products or services for multiple platforms or software environments. Engineers and developers use a variety of methods to assist different operating systems or environments for one application or product. This development approach allows you to develop an Android application, iOS application, and Windows application simultaneously.

Cross-platform application developers create a cohesive API running on top of a native SDK, make use of native IDEs, and build iOS and Android apps that share the same codebase. Native cross-platform applications are mostly built with Xamarin, React Native, Flutter, and Kotlin Multiplatform.

What is Flutter?

Flutter is a cross-platform UI toolkit that lets us create quick, beautiful, and natively compiled applications for mobile, web, and desktop using Dart programming languages. Its popularity has been growing increasingly in the past few years and will continue to increase in the coming years. Google launched Flutter as a Software Development Kit (SDK) to create modern-day mobile applications for iOS and Android. It extends an extensive toolkit along with Flutter API, framework, and widgets to create attractive and fast applications.


Features of Flutter

The following are the essential features of Flutter:

  • Open-Source; for building desktop and mobile apps.
  • Cross-platform development; permits the developer to write the code once that can run on different platforms.
  • Hot Reload; If the Flutter code is modified, changes could be seen instantly with Hot Reload, allowing developers to fix bugs quickly.
  • Widgets; Used for developing specific customizable designs. Offers two sets of widgets: Material Design and Cupertino widgets.
  • Accessible Native Features; Allows easy access to Flutter's native code, third-party integration, and platform APIs for application development.
  • Minimal code; Flutter utilizes the Dart programming with the JIT and AOT compilation method to enhance the overall start-up time, functioning, and performance of an app.

What is Kotlin?

Kotlin is a cross-platform, general-purpose, and open-source programming language. It is a statically typed language that runs on JVM and can be used everywhere Java is used. As an individual language, it offers excellent features over Java and also works well in combination with the older language. Kotlin was developed by JetBrains and announced in 2010 with a small project. The first official publication of Kotlin came in February 2016. It was created under the Apache 2.0 license. Kotlin’s multiplatform abilities permit the developers to share code, logic, and data across several platforms; IOS, Android, Web, and more.


Features of Kotlin

Following are the features of Kotlin Language:

  • Concise: Allows developers to lessen the writing of extra codes.
  • Null safety: Eliminates the NullPointerException from the code. Interoperable.
  • Interoperable: This allows the developer to easily call the Java code alongside Java can also use the Kotlin code.
  • Smart cast: It clearly restricts the immutable values and inserts the value in its safe cast automatically.
  • Tool-friendly: Easy to build programs using the command line as well as any Java IDE.
  • Extension function: Supports extension functions and extension properties helping to extend the functionality of classes without hampering their code.

TUG OF WAR BEGINS: Flutter vs Kotlin

CRITERIA 1: UI Experience

In the tug of war of flutter vs kotlin based on UI Experience, Flutter allows the use of various widgets, these widgets reduce the development time by building a mobile solution in a customized, fast, and efficient manner. Flutter It is after all a software development kit that is primarily meant to support UI developments.

Kotlin on the other hand enables developers to have a bird's eye view of the execution, conduct, and appearance the way they want things to work out in the application. It does not set any restrictions or pre-conceived guidelines, thereby enabling developers to utilize local widgets and libraries. This makes Kotlin quite similar to native app development.

CRITERIA 2: Testing Support

Flutter offers the user a rich set of testing features that do unit testing for widgets while incorporating the level. Having great documentation on testing, it also has a fascinating widget testing feature. With the help of this feature, the user makes widget tests to examine the UI, and operate them at unit test speed. Looking at the other aspect of Flutter vs Kotlin, when a developer is considering the backend development services, Kotlin is one such platform that has an advantage over the others in the market. Though Flutter operates with Firebase, which is an effective Backend as a Service Platform securing backend opportunities, Kotlin further allows developers to generate the backend code.

CRITERIA 3: Community Support

The comparison of Flutter vs Kotlin gets tough when it comes to community support as both the cross-development platforms have great community participation. But evaluating the freshness of the Flutter framework, indifference to Kotlin, it has more active membership participation and escalating popularity. The Flutter documentation is also pretty detailed and up to date. It is a great place for anyone without preceding knowledge of the framework to start with, as it also provides information based on the learning curve and experience.


When it comes to speed, Flutter performs well but lags in a few things when compared to Kotlin. The tough competitor in the Flutter vs Kotlin loop, Kotlin is typically faster as it composes to the format of the target platform. If speed is a HUGE consideration, Kotlin is surely the better candidate.

CRITERIA 5: Integration of third-party libraries and tools

Kotlin works within the ecosystem of the native platform in place of having its own. It empowers app developers to deploy the same libraries and third-party tools that they were using while natively developing applications such as SwiftUI and Jetpack Compose. Kotlin also gives developers the advantage of not looking for tools and libraries to connect with the native environment. 

On the other hand of Flutter vs Kotlin based on integration with third-party libraries and tools, Flutter SDK allows the calling of platform-certain APIs as available in iOS and Android languages such as Swift, Objective C, and Java. These platform-specific languages are not reliant on code generation but make full use of flexible messaging.  

TUG OF WAR: Flutter vs Kotlin, CONTINUES...







Developed By

framework first introduced by Google.

programing language first introduced by JetBrains.


Dart programming language to build mobile applications.

Itself a programing language that uses Java, JVM, JavaScript, and Native for creating applications.


On GitHub has 88.7k stars and 11.7k folks.

On GitHub has 31.1k stars and 3.8k folks.


Amazing, as it uses Dart programming, and no need to use JavaScript Bridge for starting interactions with the app.

Slightly slow, as it uses JavaScript and 100% interoperable in Java that decreases the speed of an application.

App Size


Less as compared to Flutter.

Learning curve

Developers must have to learn Dart programming to build an application.

Easy learning curve as it is very similar to Java.


Entirely free to utilize this system technologies and their libraries.

Also, free!

Deployment Options

Can deploy on Mobile, Desktop, and Web.

Can deploy on Mobile, Desktop, and Web.

Popular Apps

Hamilton, Google Ads, Alibaba, Cryptograph, etc.

Pinterest, Coursera, Evernote, etc.

Advantages and Disadvantages: Flutter vs Kotlin



  • Great performance
  • Apt for scalability
  • Easy learning curve
  • Great community support and maintenance


  • Expensive development cost
  • Increased app development timeframe
  • Fewer third-party libraries



  • Quicker application development timeframe
  • Hot reload feature
  • Elegant user interfaces
  • Fantastic community support
  • Low-cost app development


  • Larger app size
  • Newer framework ecosystem
  • The fairly new job market


In the era of many technologies and offerings, getting to one that is perfect in everything is kind of impossible, therefore, in this tug of war, Flutter vs. Kotlin, the winner cross-development application may hold a lot of amazing things but have some disadvantages at the same time.

If very heightened UI levels are not on the top of the list and you are in a hurry to launch the app somehow, flutter will make it a good choice. This is so because it offers end-to-end development. Things would be done for your satisfaction. However, if you want to carry out an enhanced and customized user interface that is high on business logic—nothing can beat Kotlin.

Therefore, in answer to the question of which cross-development application, Flutter vs Kotlin, to choose in 2021, the tug of war is well won by Kotlin.