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monix / monix


Asynchronous, Reactive Programming for Scala and Scala.js.



Asynchronous, Reactive Programming for Scala and Scala.js.

Build Status Coverage Status Scala.js Maven Central



Monix is a high-performance Scala / Scala.js library for composing asynchronous and event-based programs using observable sequences that are exposed as asynchronous streams, expanding on the observer pattern, strongly inspired by ReactiveX, but designed from the ground up for back-pressure and made to cleanly interact with Scala's standard library and compatible out-of-the-box with the Reactive Streams protocol.


  • exposes the kick-ass Observable, Task and Coeval
  • modular, only use what you need
  • the core has no third-party dependencies
  • strives to be idiomatic Scala and encourages referential transparency, but is built to be faster than alternatives
  • is a Typelevel project
  • designed for true asynchronicity, running on both the JVM and Scala.js,
  • really good test coverage and API documentation as a project policy


See monix-sample for a project exemplifying Monix used both on the server and on the client.


The packages are published on Maven Central.

  • Current stable release: 2.3.0

For the current stable release (use the %%% for Scala.js):

libraryDependencies += "io.monix" %% "monix" % "2.3.0"


Monix 2.x is modular by design, so you can pick and choose:

  • monix-types exposes type-classes and shims needed for integration with other FP libraries (Cats, Scalaz)
  • monix-execution exposes the low-level execution environment, or more precisely Scheduler, Cancelable, Atomic and CancelableFuture
  • monix-eval exposes Task, Coeval and depends on monix-execution and monix-types
  • monix-reactive exposes Observable streams and depends on monix-eval and monix-types
  • monix provides all of the above

Optional packages:

  • monix-cats provides integration with Cats and depends on monix-types and org.typelevel.cats-core
  • monix-scalaz-72 provides integration with Scalaz and depends on monix-types and org.scalaz.scalaz-core version 7.2.x


NOTE: The documentation is a work in progress. All documentation is hosted at, contributions are welcome:

API Documentation:



The current maintainers (people who can help you) are:


The Monix project welcomes contributions from anybody wishing to participate. All code or documentation that is provided must be licensed with the same license that Monix is licensed with (Apache 2.0, see LICENSE.txt).

People are expected to follow the Typelevel Code of Conduct when discussing Monix on the Github page, Gitter channel, or other venues.

Feel free to open an issue if you notice a bug, have an idea for a feature, or have a question about the code. Pull requests are also gladly accepted. For more information, check out the contributor guide.


All code in this repository is licensed under the Apache License, Version 2.0. See LICENCE.txt.


YourKit supports the Monix project with its full-featured Java Profiler. YourKit, LLC is the creator [YourKit Java Profiler]( and [YourKit .NET Profiler](, innovative and intelligent tools for profiling Java and .NET applications.

Development of Monix has been initiated by Eloquentix engineers, with Monix being introduced at E.ON Connecting Energies, powering the next generation energy grid solutions.