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A concise multiplatform language developed by JetBrains
With 2.5 million developers worldwide using Kotlin, the language continues to thrive and evolve. From exciting language and ecosystem updates and robust AI tools that empower Kotlin development to major Kotlin Multiplatform milestones and a strategic partnership for the backend, KotlinConf 2025 brought a wave of news that set the tone for the year ahead. Here’s everything you need to know.
Kotlin 2.2 and language evolution
Kotlin 2.2 is on the horizon – and it brings a fresh set of features, including:
- Guard conditions in when-with-subject
- Multi-dollar interpolation
- Non-local break and continue
- Context parameters in Beta
K2 compiler: Now the default in IntelliJ IDEA 2025.1
K2 mode has become the default in IntelliJ IDEA 2025.1, meaning that your IDE now reuses parts of the much faster K2 compiler for code analysis.
You can see the significant decrease in compilation time for the IntelliJ monorepo, which includes nearly all JetBrains projects, covering over twelve million lines of Kotlin code.
When we turned on K2 mode for the repo, compilation time dropped by over 40%.
New language features on the way
While build speed was a major motivation behind the K2 compiler, we had another key goal in mind: enabling a steady, high-quality rollout of new language features.
We aim to continuously make Kotlin more ergonomic, improve its type safety, and speed up the core feedback loop. Upcoming language features include:
- Positional destructuring
- Name-based destructuring
- Enhanced nullability
- Rich errors
- Must-use return values
- `CheckReturnValue`
We also know that great language features are only part of the story. Compiler plugins play a crucial role in enabling new programming paradigms. With the K2 compiler, we’re now more confident in the stability of the compiler internals. We’re also designing a stable compiler plugin API for the frontend, making it easier to extend the compiler with custom checks and code generation.
Kotlin build tool innovation – Amper
Amper, our experimental Kotlin and JVM build tool, continues to evolve on its road to Alpha. Like Kotlin, it’s developer-friendly, and you can build extensive tooling for it. Amper also has a clear configuration path, IDE support, and error reporting. It supports all the capabilities of Kotlin, whether you are writing a multiplatform application, a backend implementation with a Spring or Ktor client, or a command-line tool.
Growth of the Kotlin Foundation and reopening of the Grants Program
The Kotlin Foundation is expanding this year with the addition of two new members. Block, Inc. joins as a Silver Member, and Meta joins as a Gold Member. Their support helps us further our mission of advancing the Kotlin ecosystem and driving Kotlin’s widespread adoption.
For the past two years, the Kotlin Foundation Grants Program has celebrated standout open-source contributions to the community. We’re proud to recognize the 2024 winners: Konsist, Compose Rich Editor, Multiplatform Settings, Ultron, and Orbit MVI.
And good news – the Grants Program is reopening this year! If you’re building something impactful in the Kotlin ecosystem, this is your chance to apply for a grant and get recognized. We can’t wait to see what you create.
Introducing Koog: A framework for building AI agents in Kotlin (now open source)
Kotlin and AI are increasingly intertwined. You can now build everything with AI in Kotlin and get AI-powered support while doing it.
Today we’re open-sourcing Koog, a new framework for developing advanced and reliable AI agents in Kotlin. It includes predefined workflows and patterns, which you can use directly or combine with each other. You can now pair LLM intelligence with Kotlin’s expressiveness to develop AI-powered apps.
On the flip side, AI is here to assist Kotlin developers, whether you’re working on server-side apps, Android applications, multiplatform projects, or even AI agents.
JetBrains AI is deeply integrated into our IDEs, offering smart features. You can chat with AI about the codebase, ask project-specific questions, and get context-aware answers.
Code completion is powered by Mellum, JetBrains’ own LLM designed specifically for code-related tasks. It’s fast, accurate, and designed to be used in production on large codebases. There’s now a version fine-tuned specifically for Kotlin. Today we’re open-sourcing it to make it available for the broader developer and research community.
Recently, we also introduced Junie, an AI coding agent capable of performing complex tasks across all types of Kotlin applications – from server-side and Android to Kotlin Multiplatform. We’re going to open the EAP for Junie on GitHub soon. Stay tuned!
Kotlin Multiplatform: New KMP plugin in IntelliJ IDEA + Android Studio and Compose Multiplatform Updates
Kotlin Multiplatform is also getting several major updates, including Kotlin Multiplatform support in JetBrains IDEs and Android Studio and Compose Multiplatform for iOS officially reaching Stable status. Here are some of the main highlights announced during the keynote:
- There’s a brand-new KMP plugin for IntelliJ IDEA and Android Studio – learn more.
- The first experimental release of Swift Export is coming in Kotlin 2.2.20.
- Compose Multiplatform for iOS is now Stable.
- Compose Hot Reload is here.
Compose Multiplatform for iOS is Stable
Compose Multiplatform for iOS is now Stable and ready for production. It gives you everything you need to build beautiful, responsive apps on iOS – with native-like scrolling, iOS-native text selection, drag-and-drop functionality, variable font support, and natural gestures.
On top of that, Compose Hot Reload is already available. It lets you update your UI and see changes instantly – no restarts, no state loss. Enjoy faster iteration and smoother development.
Kotlin/Wasm and Compose for web progress
The web target for Compose Multiplatform continues to evolve, with ongoing performance improvements and web implementations for more APIs, bringing it even closer to feature parity with our other platforms.
Meanwhile, Kotlin/Wasm is improving rapidly, with faster incremental builds, smaller output binaries, and a better developer experience. Both Kotlin/Wasm and Compose Multiplatform for web are expected to reach Beta later this year.
Kotlin for server side: Growing adoption and Spring partnership
Nearly half of all Kotlin developers use the language on the backend – a number worth celebrating! And there’s a lot of amazing work being done with server-side Kotlin today.
Watch the showcase video to hear from the teams putting it into action.
To support this momentum, JetBrains is partnering with the Spring team to make Kotlin a top choice for professional server-side work. The areas of collaboration include:
- Full null safety for Kotlin and Spring apps
- Official learning materials in Kotlin
- Faster Kotlin reflection with `kotlinx.reflect`
Backend ecosystem: Ktor 3 and revamped Exposed
Ktor 3 brings big improvements to the core, including up to 3x faster I/O performance, enhanced configuration support, and new features like server-sent events, WebAssembly support, and more.
Ktor’s adoption is growing fast – up 37% over the last year, and we continue to enhance its feature set to meet your needs as users of the framework.
The Exposed library has been fully reworked. Thanks to the rewritten core of the library, support for new SQL concepts, and better documentation and onboarding materials, working with Exposed has really levelled up, and with its new plugin, you can enjoy first-class IDE support.
Official Kotlin LSP in development
Last but not least, Kotlin is expanding to more development environments – starting with the official Kotlin Language Server Protocol (LSP) and a new Kotlin extension for Visual Studio Code. Although still in its early stages, it already includes basic support for code completion, navigation, inspections, quick-fixes, Java interoperability, and basic project import. An Alpha release is planned for later this year, with much more to come. In the meantime, you can experiment with the pre-Alpha build and share your feedback with us.
Wrapping up
We’re incredibly grateful to the Kotlin community for shaping the language, sharing feedback, and pushing boundaries. The wide range of updates set the stage for an exciting year ahead.
Let’s build the innovative and ambitious future of Kotlin together!
Missed the keynote? We’ll also be live-streaming the main track, featuring sessions from the heart of the event. Watch now!
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