Kotlin 2.1 Released: What's New in the Language for JVM and Multiplatform

Kotlin 2.1 is Out: What Changed in JetBrains' Programming Language

The JetBrains team has officially announced the release of Kotlin 2.1 — a significant update to the popular statically typed programming language. The new release brings stabilization of key features of the K2 compiler, expanded capabilities for multiplatform development, and a number of performance improvements. Let's break down the main changes.

Stable K2 Compiler: Performance and New Features

The main innovation of version 2.1 is moving the K2 compiler to stable status. Previously available as a preview, K2 is now the default compiler for all targets: JVM, Native, JS, and multiplatform. This has led to a significant increase in build speed (up to 20-30% faster in a number of projects) and improved code analysis.

Key compiler improvements:

• Optimization of inline functions — the compiler now handles inline functions better, reducing the size of the generated bytecode.
• Improved type inference — K2 more accurately determines types in complex call chains, reducing the need for explicit annotations.
• Support for new syntax — experimental constructs have been stabilized, including enums with generics and improved work with value classes.

Experimental Features: What Appeared in Kotlin 2.1

Although K2 has become stable, the JetBrains team continued to introduce experimental capabilities. Version 2.1 includes:

• Non-local break and continue — a long-awaited feature that allows using these operators inside lambda expressions, simplifying work with loops in a functional style.
• Named arguments in lambdas — you can now pass named arguments to lambda expressions, which improves code readability when working with higher-order functions.
• Context receivers — an extension of the context receiver mechanism, simplifying dependency injection without explicitly passing parameters.

Kotlin Multiplatform: Improvements for Cross-Platform Development

Kotlin 2.1 has significantly enhanced support for multiplatform projects. The main changes include:

• Unified memory model for Native — all platforms (JVM, Native, JS) now use a single memory management model, simplifying code portability.
• Improved integration with Compose Multiplatform — APIs for working with animations and gestures in declarative UI have been stabilized.
• Support for Android SDK 35 — updated libraries and compatibility tools with the latest versions of Android.

Fixes and Performance

The release includes over 200 bug fixes, including those related to coroutines, serialization, and Gradle plugins. Developers noted a reduction in memory consumption in the IDE when analyzing large projects.

The update is available for download via the official JetBrains website and the SDKMAN package manager. To upgrade to Kotlin 2.1, simply update the plugin version in IntelliJ IDEA or Android Studio and change the version number in the build.gradle.kts file.

Kotlin 2.1 confirms its status as one of the fastest-developing