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Kotlin, as a language, provides only minimal low-level APIs in its standard library to enable various other libraries to utilize coroutines. Unlike many other languages with similar capabilities, async and await are not keywords in Kotlin and are not even part of its standard library. Moreover, Kotlin's concept of suspending function provides a safer and less error-prone abstraction for asynchronous operations than futures and promises.

kotlinx.coroutines is a rich library for coroutines developed by JetBrains. It contains a number of high-level coroutine-enabled primitives that this guide covers, including launch, async and others.

This is a guide on core features of kotlinx.coroutines with a series of examples, divided up into different topics.

In order to use coroutines as well as follow the examples in this guide, you need to add a dependency on kotlinx-coroutines-core module as explained in the project README.

Table of contents

• Coroutine basics
• Cancellation and timeouts
• Composing suspending functions
• Coroutine context and dispatchers
• Exception handling and supervision
• Channels (experimental)
• Shared mutable state and concurrency
• Select expression (experimental)

Additional references

• Guide to UI programming with coroutines
• Guide to reactive streams with coroutines
• Coroutines design document (KEEP)
• Full kotlinx.coroutines API reference