Choosing Kotlin vs Flutter for Your Next Application
The platform you choose for implementing your apps is the single most impactful decision you'll make in the early stages of your project. Performance, usability, scalability, and longevity will all be determined by the technologies you choose more than almost anything else. Both Flutter and Kotlin have grown in popularity and have been used year after year for precisely this reason. Each technology offers a unique, performant, and capable solution that attracts high-quality development teams.
Our top-rated Android development companies routinely use both technologies to implement client applications with the best available tools for each role. Here, we help you to take a close look at when you should use Kotlin vs Flutter, how to compare the two distinct technologies, and find the best route to build effective decision-making when it comes to all your technology challenges.
Throughout this article, we closely compare the Flutter framework and Kotlin language, take a detailed look at cross-platform vs native app development, and analyze the Google software kit vs Google's language tools to decide how each technology fits into your development teams.
What is Kotlin?
The most important point to note when comparing these two technologies is the variable, though overlapping, roles they play in the technology stack. Kotlin is a general-purpose programming language used for a wide range of software development applications. In 2017, Google adopted Kotlin as an official language of Android development and later moved the language to preferred status in 2019.
Kotlin is most widely appreciated as a successor to the Java language, taking advantage of the JVM (Java Virtual Machine) and the tools that support the language. Many of the top Java development companies available today have a growing interest, knowledge, and experience with Kotlin development.
Similar to Flutter, Kotlin supports cross-platform application development using the Multiplatform Mobile SDK to share application logic between apps across diverse platforms. The emergence of a modern programming language with cross-platform capabilities and an exceptional set of development tools has resulted in Kotlin booming in popularity in recent years.
What is Flutter?
In technical terms, Flutter is an SDK (software development kit) designed to produce cross-platform applications across mobile, desktop, and the web among other modern platforms. In practical terms, Flutter is a framework used by software engineers to develop applications targeting these platforms with Dart code.
Similar to Kotlin, Flutter is a relatively new technology to developers. First released as an alpha in 2017, the framework initially grew as a mobile development tool before expanding to include additional domains with recent updates. In the short time Flutter has been available, its use has rapidly grown among developers to surpass even React Native as the most popular cross-platform tool.
Our ultimate guide to Flutter development has a detailed breakdown of the technology and its use, including everything you need to understand and get started in practical Flutter development.
Pros and Cons of Flutter vs Kotlin
Between Kotlin and Flutter, each technology has advantages and drawbacks that set them apart from each other and from other competing tools. To accurately compare one against the other we need to take a look at the pros and cons of each technology and find out where we should use each tool for maximum effect, or opt for a different solution entirely.
Pros of Flutter Development
Exceptional UI Customisation
Flutter has put UX and UI considerations front and center in the framework's design priorities. High-quality user interactions are key to the success of Flutter applications and the promotion of services the platform supports. Flutter widgets allow developers to build interfaces from inherently reusable components tailored to each target platform.
While many frameworks restrict what developers can do when it comes to UI and layout, Flutter boasts of providing “control over every pixel” to allow developers to build their apps precisely as they imagine them.
Rapid Application Development
Another key advantage of Flutter is the chance for developers to reduce the time-to-market for future applications. By creating opportunities for more modular engineering, increased code reuse, and improved development tooling — Flutter enables developers to do more with their code and unlock efficiency and productivity in their teams.
Recent versions of Flutter enable development across mobile, desktop, and the web in addition to a range of smart devices in automotive and consumer technology spaces. This development boost is one of the key reasons this technology has seen a surge in popularity in recent years.
High-Quality Developer Support
Since the release of Flutter, the platform has richly benefited from vast amounts of developer feedback and support to create a suite of tools and technologies that are difficult for other technologies to match. Recent improvements to the platform have included Hot Reload, continuous integration tooling, IDE improvements, and the outstanding documentation that has come to be associated with Google products.
These tools are improving the productivity and efficiency of Flutter while enhancing the user experience of developers leaning on the technology daily.
Cons of Flutter Development
While Flutter's popularity and use have contributed to the framework rapidly maturing since its release — practically speaking, the technology has only been available in a production-ready state over the last 5 years. Xamarin, in comparison, has been around for well over a decade while many web frameworks and tools have been in use for over twenty years. This maturity problem is only compounded by Flutter's reliance on the relatively new Dart programming language.
There are fewer development teams familiar with Flutter and Dart in comparison to other technologies out there. This is an issue that can make the right developers hard to find and costly to retain.
Larger Application Footprint
Flutter's biggest advantage, its in-built rendering engine that provides much of the platform's performance characteristics, has some drawbacks of its own. By including everything an app might need right out of the box, the size of even a relatively minimal Flutter application is forced to grow as a result.
The rendering engine, widgets, and internal tools that a Flutter app depends on take up a significant amount of space. In some scenarios, this will be a significant factor in convincing users to download and run an application on an already crowded device. This restriction effectively rules out Flutter as a technology platform for building iOS or Android instant apps.
The other major advantage of Flutter, its exceptional UI and UX credentials, can also be a drawback for some applications and use cases. While Flutter's UI tools make it easy for apps to be consistent with each other across multiple platforms, it makes it more difficult for individual apps to be completely consistent with the platform they run on.
Users will note a slight shift in design and style from the platform's native buttons and animations when loading a Flutter-based app. This shift can be a minor note to be aware of in some cases or a major issue for certain types of applications. Google has published two sets of widgets to bridge iOS and material design differences but some departures in native style and layout are something for designers to keep in mind.
Pros of Kotlin
Modernized Programming Language
One of the biggest advantages to Kotlin is that its designers have had a chance to re-write the rule book when creating the language. This means modernization in tools and techniques for developers to take advantage of when designing future applications. Improvements to null safety, efficiency, and maintainability are three key reasons that the language is rapidly growing in popularity and use.
Compared to Java, Kotlin has a suite of syntax, performance, and reliability improvements that have emerged from a modernized design. This marks one of the key reasons the language was chosen as the primary tool for Android development in 2019.
Interoperable with Java
Kotlin and Java are entirely interchangeable when it comes to building and implementing apps for either mobile or desktop. For developers new to Kotlin or those new to mobile development in general this is a feature that can speed up learning and deployment of the language by a significant degree.
Complete interoperability between the two languages means that developers can migrate apps in discrete units of code rather than re-design the entire codebase right from the ground up. The good news for engineers is that many of the tips and guides to being a better Java developer also apply to Kotlin application development.
Reduced Boilerplate Code
One of the greatest advantages of Kotlin is its ability to reduce the amount of boilerplate code necessary to build applications. Data classes, inline functions, and properties combine together to create a modern language capable of handling the demands that mobile app development places on it.
This unique advantage of Kotlin is something that can save developers time and provide a much-needed most in morale and motivation by allowing the focus to be shifted to the most interesting, challenging, and critical areas of an application.
Cons of Kotlin
Comparatively Limited Resources
Despite Kotlin growing in popularity day by day, there's still a limited number of resources, developers, and tools available for the language in comparison to more mature solutions. This problem is similar to the one faced by Dart developers and teams. It's worth noting, however, that these challenges become less and less significant every month.
Despite the Kotlin language having many similarities to Java, it's still a technology that will require some time for developers to get to grips with its features and make full use of its advantages.
Decrease in Compilation Speed
When it comes to runtime performance, Kotlin code is typically head and shoulders above comparable Java applications. In compilation performance though, Java has a significant edge that could cost valuable iterations, CI (continuous integration) issues, or simply lead to more frustrated developers.
Kotlin's optimizations and streamlined resources come with many advantages, but can trade off compilation performance as a result.
False Sense of Security
The improvements that come to Kotlin over Java are extremely valuable in software engineering projects. Null safety, language improvements, and coroutines all have a valuable place in modern software engineering but they shouldn't be depended on exclusively for security.
Kotlin's null safety, for example, can be overwritten by allowing non-null variables to be initialized late. Developers not expecting null exceptions in Kotlin code could be easily caught out by a relatively small slip-up.
Kotlin vs Flutter for Modern Application Development
When it comes to choosing the best outright tool for modern cross-platform application development there really isn't a clear and definitive answer.
Flutter is an exceptional application framework with a rich set of development features, elegant UI design, and represents a low-cost entry into software engineering. Yet, teams with vast knowledge and experience in the technology are still comparatively hard to come by. Additionally, using Flutter for some types of projects limits the ability to create mobile-based instant apps and could limit the target audience as a result.
Kotlin, in comparison, is an excellent programming language that can offer remarkable runtime performance, robust and reliable applications, and highly-maintainable cross-platform code. On the other hand, it's also a language likely to increase development costs over Flutter, offers fewer resources and tools in comparison to related languages, and can add complexity to a project rather than reduce it.
Each of the advantages and drawbacks to both Kotlin and Flutter needs to be carefully examined, investigated, and thought out in relation to your own particular projects and use cases. Each technology will have a potential role to play in specific teams, projects, and organizations. How you use them to their full potential is entirely up to you.
Q1. Is Kotlin better than Flutter?
Both Kotlin and Flutter are exceptionally performant and productive tools when it comes to modern application development. Kotlin, a general-purpose programming language first released back in 2011, is an exceptional tool for creating performant applications.
In comparison, Flutter is a cross-platform framework used to create applications that target Android, iOS, desktop, and the web. Both tools can create remarkable applications for a wide variety of platforms and use cases. Both Kotlin and Flutter have advantages and drawbacks that make them well worth considering for different types of projects across different teams of developers.
Since Flutter's launch in 2017, Google's application framework has rapidly grown in popularity to surpass Kotlin and even React Native to become the most popular application framework currently available. While no technology, language, or framework is entirely perfect — either one of these two tools will allow developers to deploy exceptional applications.
Q2. Is Flutter going to replace Kotlin?
Though Flutter has seen a boom in popularity over the last 4-5 years, it's highly unlikely that the technology is going to entirely replace Kotlin or Swift in the near future.
Android recently promoted Kotlin as the primary language to use when creating native apps for the mobile platform. Since that time Java libraries, frameworks, and code has been gradually replaced by Kotlin with developers quickly migrating to the new native solution to take advantage of its unique benefits.
Flutter applications, similar to other application frameworks, still require native bindings to the underlying operating system at some level. Flutter is somewhat unique in binding to Android at a lower level than most other technologies, but the framework still relies on native code to run its applications. As a result, Flutter is unlikely to entirely replace Kotlin on Android unless Google migrates Dart to native status on Android.
Q3. Is Netflix moving to Kotlin?
Yes! In the company’s technology blog, Netflix announced that the studio's Android and iOS apps were successfully migrated to a Kotlin Multiplatform solution.
The studio announced their desire to improve client-side persistence and offline support in their mobile apps and a switch to Kotlin Multiplatform to provide that support. This switch allowed the company to decouple the underlying code from their platform, create an architecture that is shared by both the Android and iOS applications, and still allow developers to explore additional technology solutions to add to their application offering.
When launched, the company cited the recent maturing of the technology as one of the key reasons for adopting it into their tech stack. Improved iOS build tools and simplification of the maintenance and integration necessary between the two platforms made the choice an easy one for project managers at Netflix to make.
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