official JetBrains project GitHub license Download

Library support for Kotlin coroutines in Kotlin/JVM and Kotlin/JS. This is a companion version for Kotlin 1.2.50 release.

launch {
    println("Hello from Kotlin Coroutines!")


  • common — common coroutines across all backends:
    • launch and async coroutine builders;
    • Job and Deferred light-weight future with cancellation support;
    • delay and yield top-level suspending functions.
  • js — Kotlin/JS implementation of common coroutines with Promise support.
  • core — Kotlin/JVM implementation of common coroutines with additional features:
    • CommonPool coroutine context (default on JVM);
    • Channel and Mutex communication and synchronization primitives;
    • produce and actor coroutine builders;
    • select expression support and more.
  • reactive — modules that provide builders and iteration support for various reactive streams libraries:
    • Reactive Streams, RxJava 1.x and 2.x and Project Reactor.
  • ui — modules that provide coroutine dispatchers for various single-threaded UI libraries:
    • Android, JavaFX, and Swing.
  • integration — modules that provide integration with various asynchronous callback- and future-based libraries.
    • JDK8 CompletableFuture, Guava ListenableFuture, and synchronous networking/IO.


Using in your projects

Note that these libraries are experimental and are subject to change.

The libraries are published to kotlinx bintray repository, linked to JCenter and pushed to Maven Central.


Add dependencies (you can also add other modules that you need):


And make sure that you use the latest Kotlin version:



Add dependencies (you can also add other modules that you need):

compile 'org.jetbrains.kotlinx:kotlinx-coroutines-core:0.23.3'

And make sure that you use the latest Kotlin version:

buildscript {
    ext.kotlin_version = '1.2.50'

Make sure that you have either jcenter() or mavenCentral() in the list of repositories:

repository {


Use org.jetbrains.kotlinx:kotlinx-coroutines-core-js:<version> artifact in your Gradle/Maven dependencies or install kotlinx-coroutines-core package via NPM.


In obfuscated code, fields with different types can have the same names, and AtomicReferenceFieldUpdater may be unable to find the correct ones. To avoid field overloading by type during obfuscation, add this to your config:

-keepclassmembernames class kotlinx.** {
    volatile <fields>;


This library is built with Gradle. To build it, use ./gradlew build. You can import this project into IDEA, but you have to delegate build actions to Gradle (in Preferences -> Build, Execution, Deployment -> Build Tools -> Gradle -> Runner)


  • JDK >= 1.8 referred to by the JAVA_HOME environment variable.
  • JDK 1.6 referred to by the JDK_16 environment variable.

Contributions and releases

All development (both new features and bug fixes) is performed in develop branch. This way master sources always contain sources of the most recently released version. Please send PRs with bug fixes to develop branch. Fixes to documentation in markdown files are an exception to this rule. They are updated directly in master.

The develop branch is pushed to master during release.

  • Full release procedure checklist is here.
  • Steps for contributing new integration modules are explained here.
compile "org.jetbrains.kotlinx:kotlinx-coroutines:0.20-alpha-7"

Related Libraries


Korio - Kotlin cORoutines I/O - Streams + Async TCP Client/Server + WebSockets + Async Injector + Async Router + Virtual File System + Serialization (XML/Json/Yaml) + Redis + Cassandra + Elasticsearch + Amazon DynamoDB & S3 + OAuth (Google & Facebook) + Dropbox for JVM, Android, Node.JS and Browser

Last updated 3 mins ago


Korim - Kotlin cORoutines IMaging utilities depending on Korio for JVM, Android and JS

Last updated 3 mins ago


Fibers, Channels and Actors for the JVM

Last updated 3 mins ago


Kovenant. Promises for Kotlin.

Last updated 3 mins ago


async/await for Android built upon coroutines introduced in Kotlin 1.1

Last updated 3 mins ago