Kotlin Multiplatform v1.8.20-Beta Release Notes & Developer Guide

Kotlin 1.8.20-Beta advances the K2 compiler with alpha JavaScript support and WebAssembly improvements including WASI compatibility. The release delivers significant performance optimizations for range operations and inline classes, adds Base64 to common stdlib, and enhances Java interoperability through raw type support. Over 100 compiler fixes address context receivers, value classes, and cross-platform compilation issues.

Highlights

• K2 compiler reaches alpha support for JavaScript backend with improved stability
• WebAssembly backend now supports WASI and improved browser compatibility
• Custom equals and hashCode implementation for value classes on JVM
• Experimental @Volatile annotation support in Kotlin/Native
• Base64 encoding added to common stdlib for cross-platform use
• Significant performance improvements for range operations and inline class boxing
• Raw type support in FIR for better Java interoperability