Kotlin vs Flutter- Differences, Pros and Cons 

Want to grow your business with a cross-platform app but do not know which technology to choose for mobile app development? Is the Koltin vs. Flutter question haunting you?  

It is okay, you are not alone.   

A lot of businesses want to go for cross-platform mobile app development for its evident benefits such as faster time-to-market, lower development costs, and a single codebase for multiple platforms.   

However, choosing the most project-appropriate technology among various options like Kotlin, Flutter, React Native, etc., becomes an uphill battle.   

Therefore, in this blog, we will draw comparisons between Kotlin and Flutter, both Google-backed technologies, and try to address the big question, ‘Flutter vs Koltin- which is better for your next project’.  

Starting with the basics of these two cross-platform technologies, we will look at the difference between the two.   

Kotlin  

Kotlin is a free, open-source, and object-oriented programming language with static typing. It was developed by JetBrains as a small project in 2010. Kotlin was originally and formally released in February 2016.   

Then, in 2017, Google announced its support for Kotlin as the official Android programming language and integrated the programming language’s support directly into Android Studio. This allowed developers to convert previous Java (one of the official programming languages of Android development) code into Kotlin. Additionally, they can run Kotlin code alongside Java code in their projects.  

Also read: Ultimate Guide To Migrate From Java To Kotlin 

Thus, Kotlin can be used wherever Java works i.e., backend, web, desktop, etc. Moreover, this programming language has various multi-platform capabilities. These capabilities are leveraged by developers for sharing codes, business logic, and data layers with multiple platforms such as Android, iOS, etc.   

Some key features of Kotlin are:   

• JVM compatibility  
• Offers Kotlin multiplatform; can compile with JavaScript, LLVM code, and JVM bytecode 
• Null safe language; post Kotlin adoption, the Google Home team witnessed a 33% decrease in Null Pointer Exception crashes over 1 year 
• Comes with a compiler to detect errors both at compile time and during runtime  
• Smart cast; the immutable values are explicitly typecast and automatically inserted into their safe cast  
• Offers expansion of functionality of classes w/o the need to change their source code through extension function.   
• Tools-friendly and offers strong support  

Kotlin is known for its server and mobile development capabilities. It has gained a lot of popularity in a short span and has even been used by Jira and Adobe to rewrite their products in Kotlin.   

Now that we know what Kotlin is, let’s understand the programming language deeper by looking at its pros and cons.   

Pros of Kotlin  

Do you know? 67% of Android developers have said that Kotlin has increased their productivity.   

Apart from high productivity and performance, Kotlin is/has:  

• Easy learning curve: If one knows Java, learning Kotlin will be a simple task.   

• Clean and short code: Kotlin’s simple syntax makes the code more concise and comprehensible. There are fewer lines of code and hence, lesser development time and effort.   

• Secure: Shorter code that is easy to read also is secure as the room for flaws reduces early in the development phase and allows for quick mistake identification and rectification.   

• Lazy loading feature for web: This feature of lazy loading reduces app loading times. This is done by loading only the initial content of the app. This feature makes Kotlin one of the most sought-after languages for Android apps.   

Also read: How To Develop An Android Application With Kotlin? 

Cons of Kotlin  

While Kotlin is a popular programming language, it also has the following shortcomings:  

• High development costs: Kotlin offers semi-native functionalities and is also a heavy language for the creation of MVPs and prototypes. Thus, the costs related to Kotlin development are higher.   

Moreover, it is a relatively newer language, and hence, training investments must be made in order to equip the developers for development.   

• Slow compilation speed: The compilation time taken by Kotlin is more than that of Java. Only in some cases, does the former outperform the latter in terms of compilation speed.   

• Limited third-party libraries: Since the platform is in its nascent and developing stage, the access to libraries for users may be less in comparison to other, developed platforms.   

Kotlin is hence a programming language that gained a lot of popularity in a short period and comes with its own set of pros and cons. Next, we will learn about Flutter for a better understanding of Kotlin vs. Flutter.  

Flutter  

Flutter is a portable UI toolkit developed and introduced by Google in 2015. It is based on the Dart programming language. Flutter’s open-source feature allows users to build mobile, web, and desktop apps across multiple platforms such as Android, iOS, Linux, Windows, Mac, etc., using a single codebase.  

Flutter does not borrow native components from other platforms, instead, it creates its own widgets and uses a graphics processing unit (GPU) to render them. These widgets are categorized into two sets- Material Design, which implements Google’s design language, and Cupertino implements Apple’s guidelines for UIs on iOS.  

Some key Flutter features are:  

• Facilitates cross-platform app development allowing businesses to save time and project costs.   
• Customizable designs could be created using multiple available widgets.  
• Employs JIT and AOT compilation techniques as well as Dart programming to boost an app’s performance and speed.  
• Offers hot reloading feature allowing developers to spot and fix bugs quickly.   

• Makes the platform APIs, third-party integration, and native code of Flutter easily accessible.   

Flutter released its first stable version- Flutter 1.0 in December 2018. Since then, it has been regularly releasing sub-versions to offer advanced features and fix bugs. Flutter 3.7 is the current stable version that was released in January 2023.  

Now that we have learned the basics of Flutter, let’s look at its pros and cons.   

Pros of Flutter  

Flutter is one of the fastest-growing cross-platform app development frameworks due to the following reasons:   

• Hot reload feature: This feature enables developers to track changes in the code easily. The changes made on emulators, simulators, and hardware can be monitored, with real-time code updates. This could be done without having to restart or reload the whole app.  

• Faster code writing: Flutter is an easy-to-learn and use framework that allows developers the ease of development and offers a faster development timeframe. With a single codebase, they can develop apps for multiple platforms. Additionally, with features like hot reload and hot restart, the app quality is also high.  

• Strong community support: Flutter has an extensive community to support its growth and popularity. Flutter comes with extensive community support. There are plenty of guides, resources, discussions, and solutions to current issues and bottlenecks, to facilitate Flutter app development.    

• Quick creation of MVPs: Flutter facilitates quick and lower costs of Flutter app development. This makes it also ideal for building MVPs and prototypes.   

• Multiple libraries and tools: Flutter offers multiple advanced tools and libraries such as Skia Graphics Library.  

Read about why Flutter is better for cross-platform app development in details in our blog titled ‘Flutter For App Development: Why Is It Better?’.  

Cons of Flutter:   

The way a coin has two sides, Flutter also has its cons along with pros. Some of its cons are:   

• Larger app size: Flutter works well with certain app sizes that are generally large and thus, creates issues for developers working on apps optimizing app sizes for devices with limited space such as Android and iOS devices.   

• Extra coding effort in some cases: While one must be well-versed in Dart to work on the Flutter platform. But even if one isn’t, it takes not so significant time to learn it. However, this could negatively impact the project timelines, simply because time is a limited resource during projects.   

• Difficult to learn for new programmers: Flutter lacks enough tutorials and workshops for new programmers.    

Now that we have looked at the description, features as well and the pros and cons of Koltin and Flutter, let’s address the big question that is Kotlin vs. Flutter in our next question.   

Kotlin vs. Flutter  

This has been the trending question for the last few years. With both platforms gaining rapid popularity every year, businesses are confused about which one to choose for their project.   

The tabular representation of comparison between Kotlin and Flutter below will help businesses better understand the two platforms and make the most suitable choice for their next project.   

Parameters	Kotlin	Flutter
Language stack	JVM, Native, Java, and JavaScript	Dart programming language
Learning Curve	Easier to learn since it is related to Java.    However, the present focus on Kotlin multiplatform with limited documentation and resources, makes the learning curve a bit hard.	Requires skill in Dart language. And has better documentation than Kotlin.
Pre-requisites	Java programming language  Any programming language exposure. Understanding of basic concepts such as variables, syntax, and commands.	Object oriented concepts such as class, methods, objects, abstraction, inheritance. Dart programming language  Understanding of object-oriented languages such as C++ and Java.
App size	Smaller compared to Flutter	Bigger or large-sized apps
Performance	High-performance; general-purpose programming language. Apps made with Kotlin are fast, with code compiled in the same format of the platform it is written for.	High-performance; strives for 60 frames per second and  primarily targets the frontend part of the app.
Hot reload	Lacks hot reload feature.	Ensures faster app development with hot reload feature.
Third party integrations	To form a connection with the native environment, there is no need for third-party tools and libraries.	Requires third-party libraries and tools to connect to the native app environment.
Backend development scope	Kotlin multiplatform feature helps programmers to build a backend without any BaaS platform.	Partners with Firebase (backend-as-a-service-platform) to allow developers to write backend code.
Pricing	Free and open source, however, Kotlin SDK only provides semi-native features, therefore, some additional expenses may be charged.	Free and open-source; technologies and associated libraries can be utilized without cost.
Testing support	Provides testing support.	Does not provide testing support.
Documentation and community support	Limited documentation and community support.	Extensive documentation and community support.
Time-to-market	A bit slower than Flutter, however, offers more concise syntax and ensures maximum code reusability leading to faster app development.	A bit faster than Kotlin.
Platforms supported	Android, JVM, iOS, macOS, Windows, Linus, JavaScript, WebAssembly	Android, iOS, Google Fushia, web, Linux, macOS, Windows
Deployment	Deployment is restricted to mobile, desktop, and web.	Deployed beyond web, desktop, and mobile.
UI Design and Experience	Design: No preconceived regulation.   Experience: Offers a free environment for the creation of app’s UIs; does not restrict UI development styles, allow developers to leverage native features whenever required or write platform-specific code.	Design: Proprietary widgets   Experience: Offers unified UI experience across each platform; manages every UI aspect in order to deliver native performance on iOS and Android with a single codebase.
Component library	Small but growing	Big and further growing

While it costs roughly between $15,000-$200,000+ to build a Flutter app, it costs between $70,000- $500,000 to build an app with Kotlin and Java.  

Read the complete cost breakdown and the factors affecting the cost of a Flutter app in our blog titled ‘How Much Does it Cost to Build a Flutter App?’.  

In the next section, we will look at the use cases for both these cross-platform technologies.   

When should you use Kotlin?   

Every technology has some areas or scenarios where it performs the best. Koltin should be leveraged when:   

• Business wants to develop a fast and lightweight app  
• A cross-platform environment isn’t needed  
• The application serves as a commercial product for the end-user; Most suitable for retail, and fintech apps  

Kotlin popularity:   

• Kotlin has 46.1k stars, 1.5k watchers, and 5.7k forks on GitHub.   

• As per the StackOverflow Developer Survey 2020, Kotlin was the 4th most loved programming language.   

• As per the 2022 survey, it is used by 9.16% of developers worldwide, with a median yearly salary of $55,071 in 2021 which increased to $69,318 in 2022. 

Popular apps made using Kotlin:   

More than 95% of the top 1000 Android apps contain Kotlin code. A large number of leading brands use Kotlin for production, including Philips, Netflix, Leroy Merlin, and VMware.  

Some of the most popular apps made using Kotlin are:  

• Netflix  
• Airbnb  
• Twitter  
• Adobe  
• Swiggy  
• Duolingo  
• Trello  

When should you use Flutter?  

Flutter gives the best results when:   

• A business needs to build an MVP with responsive widgets and mobile features and has time and budgetary constraints  
• When a business needs to build a single code with front-end and back-end functionality   
• When an e-commerce store, or banking and finance app needs to be built  
• Suitable for medium to large businesses, especially for suppliers and franchises  

Also Read: 11 Best Practices of Flutter You Must Know 

Flutter popularity:   

• Flutter has 158k stars, 3.6k watchers, and 26.2k forks on GitHub.   

• As per the StackOverflow Developer Survey 2022, Flutter was one of the most popular and wanted cross-platform tools. Moreover, it was used by 12.64% of developers globally.   

Popular Flutter apps:   

Many big brands have trusted Flutter for their app development. Some of them are:   

• Google for Google Ads, Pay, etc.  
• eBay for eBay Motors  
• Alibaba for Xianyu  
• BMW for MyBMW  

Conclusion  

Therefore, in this Kotlin vs. Flutter dilemma and debate, we think that both technologies have their strengths and weaknesses and are more suitable for certain uses/scenarios. Moreover, the choice depends upon the business size, budget, and most importantly, the project requirements.

Moreover, Flutter is a framework while Kotlin is a programming language, so no clear winner could be announced between the two.

The safest bet for a business is to consider its unique requirements and consult a suitable, experienced, and reputable software development company such as BigOhTech or a dedicated development team to choose the most relevant cross-platform technology for its next project.