Kotlin vs. Swift: What’s the Difference?

One of the most critical decisions in mobile application (app) development is choosing the right programming language. As of 2025, Android remains ahead in the global mobile operating system race with a nearly 72 percent market share, followed by Apple’s iOS at 27.65 percent [1].

Swift is Apple’s preferred language for iOS development, while Kotlin, backed by Google, is an optimal choice for Android app development. Since their release—Kotlin in 2016 and Swift in 2015—both languages have gained widespread popularity among developers [2,3].

Discover more about Kotlin versus Swift and what sets these programming languages apart, including their strengths and potential limitations.

What is Kotlin?

JetBrains’ Kotlin is a statically typed, free-to-use general-purpose programming language. An estimated 60 percent of Android developers choose Kotlin for its strong capabilities in functional programming [4]. By supporting full Java interoperability, Kotlin makes it possible to integrate Java libraries and frameworks into Kotlin projects. 

What is Kotlin used for?

While Kotlin is primarily associated with Android development, its versatility makes it well suited for server-side web development, client-side web development, desktop applications, multiplatform library development, and data science tasks, including putting machine learning models into production and building data pipelines. 

Even as Java leads in enterprise application development, Kotlin is drawing attention for its streamlined syntax and advanced features such as null safety and invariant arrays. Amazon Web Services (AWS), for instance, reworked the code for its Quantum Ledger Database, switching from Java to Kotlin, which resulted in an improved user experience. Fast food giant McDonald’s relies on Kotlin Multiplatform to ensure their global mobile app performs smoothly across platforms without the need for codebase redundancies.

Is Kotlin compatible with iOS?

Yes, Kotlin offers support for iOS. Kotlin Multiplatform enables code sharing across mobile platforms, allowing you to reuse application logic between iOS and Android apps. 

Pros and cons of Kotlin

Kotlin-based Android apps have a 20 percent lower crash rate, making them more reliable for end-users [4]. However, Kotlin also comes with certain limitations. The following breakdown outlines both its strengths and weaknesses.

Advantages 

With features such as interoperability, simplified syntax, and integrated safety protocols, Kotlin can make it easier to, among other things, ensure your embedded code runs smoothly and avoid coding errors, increasing productivity and streamlining your process. The following are some standout features of Kotlin in mobile app development:

• Better code readability: Kotlin improves code comprehension by reducing boilerplate code through its expressive syntax. This stripped-down code is not only functional but also easier for beginners to learn.

• More reliable code: Built-in safeguards in Kotlin offer protection against common programming errors such as null pointer exceptions.

• Smaller codebase: Due to its smaller code footprint, Kotlin is more efficient and easier to manage than Java. Kotlin’s concise code can save you time and increase your productivity.

• Multiplatform projects: The release of Kotlin 1.2 made it possible to reuse code between Kotlin and Java Virtual Machine (JVM) and JavaScript, enabling you to reuse your code across all tiers—back-end, front-end, and mobile app—of your application. The option to reuse your code not only saves you time, allowing you to focus on adding features rather than starting anew with every project, but also decreases the chances of introducing errors with newly written code. 

Disadvantages

Although Kotlin brings many modern improvements to mobile app development, it also introduces some challenges. You may notice slower compilation times, a less mature ecosystem of tools and libraries, and a smaller community that can make it more challenging for you to find developer support.

• Reduced compilation speed: Although Kotlin offers advantages over Java, it generally has a longer compilation time, which can become a bottleneck in fast-paced development environments.

• Limited tools: Kotlin, being a relatively new language, lacks an extensive ecosystem of libraries, making it harder for you to reuse code.

• Smaller community: Kotlin’s community is still evolving, meaning you may find fewer resources or guidance on code issues.

What is Swift?

Swift, just like Kotlin, is an open source, general-purpose programming language. Developed by Apple, Swift improves upon C-based programming languages like C++ and Objective-C. As part of its modern features, Swift natively supports error handling.

What is Swift used for?

Swift is optimized for developing apps for the full range of Apple platforms, including iOS, watchOS, and macOS. In addition to mobile and desktop app development, Swift is also effective for cloud services and systems software development. 

Additionally, by combining Swift with development tools such as SCADE and Skip, among others, you can create native apps for both iOS and Android using Swift. This can help you develop more functional apps that provide a better user experience and offer enhanced performance compared to web apps. DoorDash and Airbnb are examples of popular apps developed using Swift.

Pros and cons of Swift

Swift matches C-based languages in performance while being both reliable and user-friendly. Take a closer look at its strengths and weaknesses below.

Advantages

Swift offers numerous advantages for iOS development, including a clean syntax, strong security features, and easy integration with legacy code. These features make Swift relatively easy to learn and can save you time by decreasing the chances that you might inadvertently introduce errors into your code.

• Brief and expressive syntax: Swift’s syntax closely resembles the English language, making it highly readable. For example, the keyword “var” helps you define a variable in Swift. 

• Built-in security: Swift’s design prioritizes safety by excluding entire classes of risky or unsafe code, allowing for smoother and more stable software releases.

• Fully compatible with Objective-C and C++: Swift code can integrate with older or legacy C++ and Objective-C code, simplifying the process of scaling or modernizing existing codebases.

Disadvantages

While Swift benefits from strong backing from Apple, it is still relatively new. In fact, similar to Kotlin, Swift has a fairly small developer community. While it is gaining more widespread popularity, it is still used by only 4.9 percent of professional developers [5], which may make it difficult for you to find experienced colleagues who can offer support. Other limitations of Swift include:

• Constraints on backward compatibility: The newest versions of Swift aren’t compatible with older versions, requiring you to update or modify your projects to work with the latest version.

• Lack of annotations: Unlike Kotlin and Java, Swift lacks support for annotations that link metadata with application code. This limitation can make adding context to code elements, such as classes, more challenging.

• Limited Xcode features: Xcode, Apple’s designated integrated development environment (IDE) for Swift, falls short in features like syntax highlighting, autocomplete, and compiling.

Kotlin vs. Swift: What should you choose?

Deciding between Kotlin and Swift often comes down to which operating system—Android or iOS—you’re developing for. ​​Kotlin is ideal for developing Android apps, while Swift is an excellent choice for developing Apple-centric apps.

Remember, neither Kotlin nor Swift is limiting; both languages offer the flexibility to target Android and iOS environments. In practice, however, Kotlin’s official support for Android and Swift’s deep integration with Apple’s platforms make them the preferred choices for their respective ecosystems.

What ranks do Kotlin and Swift hold in the current TIOBE index?

The TIOBE index, which indicates the global popularity of various programming languages and updates monthly, ranks Kotlin 25th and Swift 23rd among the top 50 programming languages in May 2025 [6]. These rankings take into account the global availability of skilled programming engineers, educational resources, and support from third-party vendors.

What are some common editors or IDEs for coding in Kotlin and Swift?

Official Kotlin support is available through JetBrains’ IntelliJ IDE and Android Studio. For Swift, Xcode is the main IDE, while Visual Studio Code serves as a popular alternative.

Learn more about mobile app development on Coursera

Kotlin and Swift are among the leading open source programming languages for building mobile applications. With the Meta Android Developer Professional Certificate, you can learn how to code in Kotlin, craft cross-platform applications using React Native, manage the life cycle of a mobile app using Android Studio, and more. 

With the Meta OS Developer Professional Certificate, you can gain the foundational skills needed to excel in an entry-level iOS developer role. The 12-course series in this program offers guidance on creating user interfaces (UIs) for mobile apps using SwiftUI. The final course culminates in a capstone project that requires you to develop a native iOS mobile application from scratch.