What’s New in Kotlin 1.4? Performance Boosts, Fresh Features, and Community Highlights

Over the past years we have worked hard to make Kotlin a fun, pleasant, and efficient programming language, and Kotlin 1.4 continues that effort with major performance and quality upgrades.

Community and Ecosystem

In the last 12 months more than 5.8 million people edited Kotlin code, a 1.5× increase over the previous year. According to the 2020 StackOverflow survey Kotlin ranks 13th among professional developers and is among the top‑5 most loved languages.

Companies using Kotlin include:

Server‑side: Atlassian, Adobe, ING Bank

Android: Google Home, Duolingo, Zomato

Multiplatform mobile: VMware, PlanGrid, CashApp, Mirego’s Trikot

Web: JetBrains Space, Karhoo, VisionForge (MIPT)

More than 30 000 Kotlin developers discuss on Slack and Reddit, over 90 000 follow the official Twitter account, and there are 200+ user groups worldwide.

Kotlin 1.4 Online Event

The Kotlin 1.4 online event will be streamed from October 12‑15. You can read the full article and subscribe to the live stream at the end of the page.

Focus on Quality

This release improves the overall development experience: IDE performance, stability, and faster code highlighting (1.5‑4× speedup) and autocomplete (response time > 500 ms cut in half). These gains require IntelliJ IDEA 2020.1+ or Android Studio 4.1+.

We fixed over 60 performance issues, including IDE freezes and memory leaks, and introduced a new experimental Kotlin compiler front‑end for further speed gains.

IDE New Features

JetBrains added a coroutine debugger, a flexible Kotlin Project Wizard for creating multiplatform projects, and more than 40 quick‑fixes, intentions, and inspections accessible via Alt+Enter.

New Compiler

The new compiler focuses on speed, uniformity across platforms, and an API for compiler extensions. Highlights include a stronger type‑inference algorithm and Alpha‑stage new JVM and JS back‑ends.

Language Features

Kotlin interface SAM conversion

Explicit API mode for library authors

Mixed named and positional arguments

Trailing commas

Improved callable references

Support for when with break and continue inside loops

Library Improvements

The standard library adds new collection operators, delegate‑property enhancements, and an ArrayDeque implementation. The stdlib dependency is now added automatically to Gradle Kotlin projects.

Other ecosystem updates:

kotlinx.coroutines 1.3.9

kotlinx.serialization 1.0.0‑RC

ktor 1.4.0

kotlinx.atomicfu 0.14.4

kotlinx.html 0.7.2

kotlinx‑nodejs 0.0.6

Kotlin/JVM

We encourage trying the new Alpha JVM back‑end and note that default methods are generated for Java 8 targets.

Kotlin/JS

Kotlin 1.4 introduces a new Gradle DSL with CSS and style‑loader support, improved npm handling, and an Alpha‑stage JS back‑end that generates TypeScript definitions and smaller binaries.

Kotlin/Native

Significant performance gains, better interop with Swift/Obj‑C, and simplified CocoaPods dependency management are included.

Kotlin Multiplatform

New project structure lets you share code between specific target subsets (e.g., iOS ARM64 and x64 simulators). You can declare dependencies once in shared source sets, and the Klib format continues to evolve.

We are also developing an Android Studio plugin that runs, tests, and debugs Kotlin code on iOS devices and simulators, with a public preview coming soon.

More Details

Full change lists and migration guides are available on the Kotlin 1.4 “What’s New” page and in the compatibility guide.

How to Help Improve Kotlin

The Kotlin plugin in IntelliJ IDEA and Android Studio can collect anonymous usage statistics. Enabling this helps the team understand which features work well and where to focus effort.

Top Issue Reporters Since Kotlin 1.3

Igor Wojda (145 issues), Louis CAD (87), Marc Knaup (86), AndroidDeveloperLB (83), Robert Stoll (68), Morgan Bartholomew (62), Victor Turansky (54), Guan Tianyi (51), Scott Pierce (38), Andreas Malik (37), Steven Schäfer (37), Björn Kautler (36), Róbert Papp (34), Toshiaki Kameyama (30), Nicholas Bilyk (29), Michael Bailey (26), Jake Wharton (25), Lamberto Basti (24), Serge Pro (23), Egor Andreevici (21).

Get Started with Kotlin 1.4

Try Kotlin online at play.kotl.in, set the compiler version to 1.4.0 in Gradle or Maven, and update the Kotlin plugin via IDE preferences or the Plugins page. Command‑line compilers are available on the GitHub releases page.

Thanks!

Thank you to everyone who tried the EAP, provided feedback, and contributed pull requests. Your input shapes Kotlin’s evolution.