Kotlin/JS

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Score7.0

Rank#40 of 97

PriceFree

Free planYes

Runs onLinux, macOS, Web, Windows

Summary

Kotlin/JS is a Kotlin compiler target that translates Kotlin code, the Kotlin standard library and compatible dependencies into JavaScript. Projects can target browsers or Node.js, including server-side and serverless applications. It supports ES5, ES2015 and ES2020 output, along with ESM, CommonJS, UMD and AMD modules. Configuration uses the Kotlin Multiplatform Gradle plugin, which supports bundling settings and JavaScript dependencies from npm. Kotlin/JS can share common logic between web frontends and JVM backends, or between Android, iOS and web clients. Kotlin wrappers are available for React and other JavaScript frameworks, including React Redux, React Router and styled-components. Browser tests can use Karma or an experimental browser testing DSL; Node.js projects use Mocha. The documentation notes that Karma is deprecated and is not expected to receive further features or fixes. The Gradle plugin generates JavaScript source maps. Kotlin/JS is open source and free, and is listed for Linux, macOS, web and Windows.

Who it is for

It suits web developers who want to write frontends in Kotlin or share business logic with JavaScript or TypeScript codebases. It also fits developers targeting Node.js applications.

What is good

Targets browsers and Node.js.
Supports four JavaScript module systems.
Can share logic across listed client platforms.
Gradle plugin generates JavaScript source maps.
Open source and free.

What to know first

Karma is deprecated.
The alternative browser testing DSL is experimental.

Verdict

Kotlin/JS brings Kotlin code and shared logic to browser and Node.js projects. Its testing options include a deprecated browser tool and an experimental alternative.

Kotlin/JS plans and pricing

All plans

Kotlin/JS Free Kotlin compiler target for JavaScript; configured with the Kotlin Multiplatform Gradle plugin kotlinlang.org · 29 Sept 2026

Compared on accounts payable software

Invoice capture: aikotlinlang.org
Approval workflows: Yeskotlinlang.org
PO matching: Yeskotlinlang.org
Multi-entity support: Yeskotlinlang.org

Facts

Purpose: Kotlin/JS transpiles Kotlin code, the Kotlin standard library, and compatible dependencies to JavaScript.kotlinlang.org · 29 Sept 2026
Environments: Kotlin/JS projects can target browsers or Node.js.kotlinlang.org · 29 Sept 2026
ECMAScript targets: The current Kotlin/JS implementation targets ES5, ES2015, and ES2020.kotlinlang.org · 29 Sept 2026
Gradle setup: Kotlin/JS is configured through the Kotlin Multiplatform Gradle plugin, which supports bundling configuration and JavaScript dependencies from npm.kotlinlang.org · 29 Sept 2026
JavaScript modules: Kotlin/JS supports ESM, CommonJS, UMD, and AMD module systems.kotlinlang.org · 29 Sept 2026
Integrations: JetBrains provides Kotlin wrappers for React and other JavaScript frameworks, including support for React Redux, React Router, and styled-components.kotlinlang.org · 29 Sept 2026
Code sharing: Kotlin/JS can share common logic between web frontends and JVM backends, and between Android, iOS, and web clients.kotlinlang.org · 29 Sept 2026
Server-side use: The Node.js target supports server-side or serverless applications, and kotlinx-nodejs provides type-safe access to the Node.js API.kotlinlang.org · 29 Sept 2026
Testing: Kotlin/JS supports browser tests through Karma or a new experimental browser testing DSL, and uses Mocha for Node.js projects.kotlinlang.org · 29 Sept 2026
Testing limitation: The Kotlin documentation says Karma is deprecated and is not expected to receive new features or bug fixes.kotlinlang.org · 29 Sept 2026
Debugging: The Kotlin Multiplatform Gradle plugin automatically generates JavaScript source maps for project builds.kotlinlang.org · 29 Sept 2026
Support: The Kotlin documentation directs users to the #javascript channel in Kotlin Slack to discuss Kotlin/JS with the community and team.kotlinlang.org · 29 Sept 2026
Intended users: The documentation describes Kotlin/JS use cases including web developers sharing business logic with JavaScript or TypeScript codebases and developers building web frontends in Kotlin.kotlinlang.org · 29 Sept 2026