A Glimpse into Kotlin’s Future: Highlights from KotlinConf 2025

KotlinConf 2025 provided attendees with an exciting preview of the upcoming enhancements and strategic directions for the Kotlin programming language and its surrounding ecosystem. JetBrains, the language’s creator, took the stage to unveil a series of forthcoming features set to arrive in the next major update, Kotlin 2.2, as well as offering a peek at longer-term developments planned for releases beyond. This annual conference serves as a vital platform for communicating the language’s evolution, showcasing technological advancements, and fostering collaboration within the developer community. The announcements covered a broad spectrum, from core language syntax improvements and compiler advancements to significant strides in multiplatform development, innovative tooling, and strategic partnerships aimed at solidifying Kotlin’s position across various domains.

The overall sentiment conveyed at the conference highlighted a period of robust development and increasing maturity for Kotlin. The teased features and updates demonstrate a clear focus on enhancing developer productivity, improving code safety and readability, expanding the language’s reach across different platforms, and strengthening its ecosystem with better tools and frameworks. Key themes emerging from the presentations included a continued commitment to performance optimization, a deepening investment in multiplatform capabilities, the integration of artificial intelligence tooling, and strategic alliances designed to boost Kotlin’s adoption, particularly in backend development. This comprehensive approach signals JetBrains’ dedication to making Kotlin not just a modern, expressive language but a versatile and powerful tool for a wide range of software development needs.

The conference served as a catalyst for generating excitement among the Kotlin community, providing a roadmap for where the language is headed. By offering early insights into planned features, JetBrains encourages feedback and prepares developers for the changes and opportunities that lie ahead. The emphasis on both foundational language improvements and ecosystem growth underscores the holistic strategy driving Kotlin’s development, aiming to create a seamless and productive experience for developers building applications for diverse targets, from mobile and desktop to web and server-side environments. The teasers from KotlinConf 2025 paint a promising picture of a language and ecosystem that continue to innovate and adapt to the evolving landscape of software development.

Core Language Innovations in Kotlin 2.2

The upcoming Kotlin 2.2 release is poised to introduce several significant language features designed to enhance expressiveness, improve code clarity, and provide developers with more powerful tools for common programming patterns. These additions reflect ongoing efforts by the Kotlin team to refine the language’s syntax and semantics based on community feedback and the evolving needs of modern software development. The planned features aim to address specific pain points, simplify complex logic, and make Kotlin code even more robust and readable.

One notable addition coming in Kotlin 2.2 is guard conditions in when-with-subject. The when expression in Kotlin is a powerful construct for handling multiple branches based on a value. Currently, guards (additional boolean conditions) can only be used in when expressions without a subject. The introduction of guard conditions alongside a subject will allow for more concise and expressive handling of complex conditional logic. This means developers will be able to combine pattern matching on a subject with arbitrary boolean conditions within the same when branch, leading to cleaner code that is easier to understand and maintain. This feature simplifies scenarios where the logic depends on both the type or value of a subject and some other state or condition, eliminating the need for nested if statements or less intuitive workarounds.

Another interesting feature is multi-dollar interpolation. String interpolation in Kotlin, using the $ prefix, is already a convenient way to embed variables or expressions directly within strings. Multi-dollar interpolation appears to extend this capability, potentially offering more advanced or specific types of interpolation, although the precise details often involve handling complex expressions or specific formatting needs in a more streamlined manner than is currently possible. This could lead to even more concise and readable code when constructing dynamic strings, particularly in scenarios involving complex data structures or formatting requirements.

Kotlin 2.2 will also introduce non-local break and continue. Control flow statements like break and continue are typically used to alter the execution flow within loops. By default, they apply to the nearest enclosing loop. Non-local control flow, often achieved through labeled breaks or returns, allows jumping out of multiple nested loops or even out of functions in specific contexts like lambdas. Adding non-local break and continue specifically provides more granular control over loop execution, enabling developers to exit or skip iterations in outer loops directly from within inner loops or lambda functions associated with loops, improving the flexibility and expressiveness of control flow within complex nested structures.

Finally, context parameters are slated for inclusion in Kotlin 2.2. Context parameters (also known as implicit parameters) offer a way to pass parameters to functions or properties implicitly, without needing to explicitly declare them in the call site every time. This can significantly clean up function signatures, especially in scenarios where certain contextual information (like a configuration object, a logger instance, or a specific execution context) needs to be available to many functions within a scope but passing it explicitly everywhere would be verbose. This feature builds upon Kotlin’s existing capabilities for dependency injection and scope management, providing a language-level mechanism for managing ambient context, leading to cleaner and more readable code, particularly in framework development or complex application architectures.

These features, taken together, represent a solid step forward for the Kotlin language itself, offering developers more powerful and convenient ways to express their logic, handle control flow, and manage context, all contributing to the ongoing goal of making Kotlin a more productive and enjoyable language to work with.

Future Language Enhancements Post-Kotlin 2.2

Looking beyond the immediate Kotlin 2.2 release, JetBrains also provided a glimpse into potential language features that are currently in the design or experimental phase and are being considered for inclusion in future updates. These features often represent more significant changes or address more complex language design challenges, and their eventual inclusion will depend on ongoing development and community feedback. The preview offers insight into the long-term vision for Kotlin’s evolution, focusing on further refining areas like destructuring, null safety, error reporting, and API design constraints.

One set of features focuses on enhancing destructuring declarations. Destructuring in Kotlin allows extracting multiple values from objects (like data classes) or collections into separate variables in a concise way. The teased enhancements include positional destructuring and name-based destructuring. Positional destructuring, as the name suggests, would likely allow destructuring elements based on their position, which is common for pairs, triples, or components of data classes with a defined order. Name-based destructuring, conversely, would enable extracting values based on their property names, potentially offering more flexibility and self-documentation, especially when dealing with objects where the order of properties is less semantically significant than their names. These features would provide developers with more versatile tools for extracting data from complex objects, making code that works with structured data more concise and readable.

Another critical area of focus is further improving nullability. Kotlin is renowned for its strong null safety features, which significantly reduce the occurrence of null pointer exceptions. “Enhanced nullability” suggests continued work in this area, possibly introducing more sophisticated type analysis, flow analysis improvements, or new syntax to handle nullability in complex scenarios, such as interactions with Java code, generic types, or specific platform APIs. Striving for enhanced nullability demonstrates a commitment to making Kotlin code even safer and more robust in its handling of potentially null values, further reducing the risk of runtime errors.

Improvements are also planned for rich errors. The quality of error messages is crucial for developer productivity. “Rich errors” implies that future compiler versions will provide more detailed, context-aware, and actionable error messages. Instead of generic error codes or cryptic messages, developers might receive explanations of why an error occurred, suggestions for how to fix it, and pointers to relevant documentation or code locations. Enhanced error reporting significantly speeds up the debugging process and lowers the barrier to entry for new Kotlin developers, making the development experience smoother and less frustrating.

Finally, features related to API design and usage constraints were teased, including must-use return values and ‘CheckReturnValue’. Some functions return important values (like resource handles, status codes, or computation results) that must be used by the caller to avoid errors or resource leaks. Languages sometimes use annotations or language constructs to enforce that the return value of such functions is not ignored. “Must-use return values” and potentially an annotation like 'CheckReturnValue' would allow API designers to mark functions whose return values are critical, enabling the compiler to issue warnings or errors if the caller discards the result. This feature promotes safer and more correct API usage, preventing common programming mistakes related to neglecting function outputs, thereby improving the overall reliability of Kotlin applications.

These forward-looking features indicate that the Kotlin language is not resting on its laurels but is actively exploring ways to become even more expressive, safer, and developer-friendly across a wider range of use cases and programming paradigms.

The Impact of the K2 Compiler

A major highlight from KotlinConf 2025 was the status update on the K2 compiler and its growing adoption. The K2 compiler is the next generation of the Kotlin compiler, rewritten from the ground up to be faster, more stable, and more extensible. Its development has been a significant multi-year effort by the JetBrains team, representing a foundational improvement for the entire Kotlin ecosystem.

A key announcement was that the K2 compiler is now the default compiler in IntelliJ IDEA 2025.1. This is a crucial milestone, moving K2 from an experimental or optional component to the standard for the most widely used Kotlin Integrated Development Environment. Making K2 the default signals JetBrains’ confidence in its stability and performance for everyday development tasks, including code analysis, highlighting, completion, and compilation within the IDE. This integration means that the majority of Kotlin developers using IntelliJ IDEA will now automatically benefit from K2’s advantages without needing to configure anything manually.

One of the most significant advantages of the K2 compiler is its performance. JetBrains presented compelling data demonstrating the compiler’s positive impact on build times. Using K2 on the IntelliJ monorepo, a massive codebase comprising over 12 million lines of Kotlin code and encompassing most JetBrains projects, resulted in a decrease in compilation time by over 40%. This is a substantial improvement, particularly for large-scale projects where compilation speed directly impacts developer productivity and iteration cycles. Faster compilation means developers spend less time waiting for builds, leading to quicker feedback loops and a more efficient development workflow. This performance boost is a direct benefit of the K2 compiler’s re-architected internals, designed for better parallelization and more efficient processing of Kotlin code.

The maturity and stability of the K2 compiler are also opening up new possibilities for the Kotlin ecosystem. With the compiler internals becoming more reliable and well-defined, the Kotlin team is now more confident in proceeding with the design of a new stable compiler plugin API for the frontend. Compiler plugins are powerful tools that allow developers to extend the compiler’s functionality, enabling custom code analysis, generating code based on annotations or specific language constructs, and enforcing domain-specific rules. A stable API means that third-party developers and library authors can build compiler plugins with the assurance that they will continue to work with future compiler versions, fostering innovation and allowing the community to tailor the Kotlin compilation process to their specific needs. This move is expected to lead to a richer ecosystem of tools and libraries that leverage the power of the compiler, unlocking new levels of productivity and code quality for Kotlin projects.

The transition to K2 as the default compiler and the foundation for future tooling marks a pivotal moment in Kotlin’s development. It not only delivers immediate performance benefits but also lays the groundwork for a more extensible and powerful language ecosystem moving forward.

Enhancements in Build Tools and Ecosystem

Beyond the core language and compiler, KotlinConf 2025 also provided updates on tools and initiatives that are vital for the broader Kotlin ecosystem. These include advancements in build systems and the introduction of new frameworks leveraging AI.

Amper, the experimental Kotlin and JVM build tool, continues to evolve. Amper is designed to simplify the build configuration process for Kotlin projects, aiming to provide a more intuitive and less verbose alternative to existing build tools like Gradle or Maven, particularly for multiplatform projects. The update indicated that Amper now has a clear configuration path, meaning its setup and usage are becoming more well-defined and stable. Furthermore, IDE support has been enhanced, making it easier for developers to work with Amper-based projects directly within their development environments, including features like syntax highlighting, code completion for build scripts, and integrated build execution. Improved error reporting is also part of the update, helping developers quickly understand and fix issues in their build configurations. The continued development of Amper suggests JetBrains’ commitment to exploring and potentially offering a streamlined, Kotlin-native build experience, which could simplify project setup and management, especially in complex multiplatform scenarios.

In the realm of artificial intelligence, a significant announcement was the open-sourcing of Koog. Koog is described as a framework for developing AI agents in Kotlin. This initiative signals Kotlin’s entry into the rapidly growing field of AI agent development, providing a structured approach for building applications that leverage AI models and decision-making processes. Open-sourcing Koog makes the framework accessible to the entire community, encouraging collaboration and innovation in developing AI-powered applications using Kotlin. This aligns with the increasing importance of AI across various software domains and positions Kotlin as a viable language for building intelligent systems.

These updates highlight JetBrains’ efforts to not only improve the core language but also to provide robust tooling and frameworks that support emerging areas of software development, ensuring that Kotlin remains a relevant and competitive choice for developers tackling modern challenges, including simplifying builds and venturing into AI.

Advancements in Kotlin Multiplatform

Kotlin Multiplatform (KMP) continues to be a major focus area for JetBrains, aiming to provide developers with the ability to share code across different platforms while retaining the ability to write platform-specific code where necessary. KotlinConf 2025 brought several key updates demonstrating significant progress and increasing maturity in this domain.

A notable improvement is the introduction of a new plugin for IntelliJ IDEA and Android Studio specifically designed to enhance the KMP development experience. This plugin likely offers better project structure visualization, improved tooling for managing multiplatform modules, streamlined debugging across different targets, and enhanced support for platform-specific dependencies and configurations. Such IDE integration is crucial for developer productivity, making it easier to set up, develop, and maintain complex multiplatform projects.

For developers targeting Apple platforms, an exciting update is the experimental release of Swift Export coming to Kotlin 2.2.20. Swift Export is a technology that facilitates the usage of Kotlin code directly from Swift, the primary programming language for iOS, macOS, watchOS, and tvOS development. While Kotlin/Native already allows compiling Kotlin code to native binaries that can be linked with Swift projects, Swift Export aims to provide a more seamless and idiomatic interoperability layer, potentially generating Swift APIs that feel more natural to Swift developers. This feature significantly lowers the barrier for integrating shared Kotlin code into existing or new iOS projects, making KMP a more attractive option for mobile development teams working across Android and iOS. Its experimental release in 2.2.20 indicates that while it’s not yet fully stable for production, it’s becoming ready for wider testing and feedback from the community.

Compose Multiplatform, JetBrains’ declarative UI framework for building UIs across multiple platforms with Kotlin, also saw important updates. The stable version of Compose Multiplatform for iOS was announced. This is a major milestone, signifying that Compose Multiplatform is now considered ready for production use on Apple’s mobile operating system. It allows developers to build user interfaces for both Android and iOS using a single codebase and the declarative Compose API, drastically reducing the amount of platform-specific UI code required. Achieving stability on iOS opens up significant possibilities for teams looking to maximize code reuse while delivering native-feeling user experiences on both major mobile platforms.

Adding to the Compose Multiplatform story is the introduction of Compose Hot Reload. Hot Reload is a feature that allows developers to see the results of their UI code changes almost instantly, without needing to recompile and redeploy the entire application. This dramatically speeds up the UI development workflow, enabling faster iteration and experimentation. Bringing this capability to Compose Multiplatform, particularly for targets like desktop and potentially mobile during development, further enhances the productivity benefits of using Compose, making the process of building UIs across different platforms much more efficient and enjoyable.

These updates collectively represent a strong push forward for Kotlin Multiplatform, addressing key challenges related to tooling, platform interoperability (especially with Swift), and the developer experience for building cross-platform user interfaces with Compose. KMP is clearly a strategic priority, and these advancements make it a more compelling choice for developers aiming to share logic and UI code across diverse environments.

Ecosystem Growth and Strategic Partnerships

Kotlin’s success is not solely dependent on the language itself but also on the strength and breadth of its ecosystem, including frameworks, libraries, and integrations with other technologies. KotlinConf 2025 highlighted significant developments in this area, including strategic partnerships and updates to key frameworks.

A particularly noteworthy announcement was the partnership with the Spring team to improve Kotlin for server-side work. Spring is one of the most popular frameworks for building enterprise-level applications, particularly in the Java ecosystem. A formal partnership between JetBrains and the Spring team signifies a concerted effort to ensure that Kotlin remains a first-class citizen within the Spring ecosystem. This could involve optimizing Spring’s features for Kotlin idioms, improving documentation and tooling support for Kotlin+Spring projects, and potentially co-developing features that leverage Kotlin’s strengths, such as coroutines for asynchronous programming. This collaboration is expected to make Kotlin an even more attractive and seamless choice for backend developers working with Spring, further solidifying its position in the server-side domain.

The Ktor framework, JetBrains’ own asynchronous framework for creating connected applications (like web servers and clients), also received important updates in its upcoming Ktor 3 release. These updates include enhanced configuration support, likely offering more flexible and robust ways to configure Ktor applications, making them easier to set up and manage in various environments. Server-sent events (SSE) support is also being added, providing a standard way for servers to push updates to clients over a single HTTP connection, which is useful for building real-time features without the overhead of WebSockets for simple updates. Furthermore, WebAssembly support is planned, which would allow Ktor applications or parts of them to run in environments that support WebAssembly, such as web browsers or serverless functions, expanding Ktor’s potential deployment targets. These Ktor updates demonstrate continued investment in JetBrains’ native web framework, offering developers powerful tools for building modern, connected applications with Kotlin.

Finally, updates were given on the development of tooling to support Kotlin development in Integrated Development Environments beyond JetBrains’ own products. The Kotlin Language Server Protocol (LSP) and a new Kotlin extension for Visual Studio Code were mentioned as being in the early stages of development. The Language Server Protocol is a standard that allows language-specific features (like code completion, diagnostics, go-to-definition, etc.) to be provided to various code editors via a separate server process. Developing a robust Kotlin LSP implementation makes it possible to offer a rich Kotlin development experience in any editor that supports LSP, not just IntelliJ IDEA or Android Studio. A dedicated extension for Visual Studio Code, one of the most popular code editors globally, is a direct application of this effort, aiming to provide excellent Kotlin support for developers who prefer that environment. This move is crucial for broadening Kotlin’s reach and making it easily accessible to developers regardless of their chosen tooling, fostering wider adoption and community growth.

The announcements at KotlinConf 2025 collectively painted a picture of a vibrant and forward-looking language ecosystem. From core language refinements and compiler breakthroughs to significant advancements in multiplatform development, innovative AI tooling, and strategic partnerships with major frameworks like Spring, Kotlin is clearly positioned for continued growth and relevance in the software development landscape. The focus on performance, developer experience, and expanding platform reach underscores JetBrains’ commitment to making Kotlin a powerful and versatile language for building modern applications across diverse environments. The teasers provided a clear indication that the future of Kotlin is bright, promising more efficient, safer, and enjoyable development experiences for the global community.