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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 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
  • strives to be idiomatic Scala and encourages referential transparency, being built for functional programming, but is built to be faster than alternatives
  • it is a Typelevel project
  • has deep integration with Typelevel Cats
  • designed for true asynchronicity, running on both the JVM and on top of Node.js and the browser, with 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: 2.3.1
  • Milestone release: 3.0.0-M1
  • Development version: 3.0.0-$hash (see versioning scheme)

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

libraryDependencies += "io.monix" %% "monix" % "2.3.1"

Or for the milestone (that works with Cats 1.0-MF):

libraryDependencies += "io.monix" %% "monix" % "3.0.0-M1"


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

  • 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
  • monix-reactive exposes Observable streams and depends on monix-eval
  • monix provides all of the above

Versioning Scheme

The versioning scheme follows the Semantic Versioning (semver) specification, meaning that stable versions have the form $major.$minor.$patch, such that:

  1. $major version updates make binary incompatible API changes
  2. $minor version updates adds functionality in a backwards-compatible manner, and
  3. $patch version updates makes backwards-compatible bug fixes

For development snapshots may be published to Sonatype at any time. Development versions have the form: $major.$minor.$patch-$hash (example 3.0.0-d3288bb).

The $hash is the 7 character git hash prefix of the commit from which the snapshot was published. Thus, "snapshots" can be used as repeatable upstream dependencies if you're feeling courageous. NO GUARANTEE is made for upgrades of development versions, use these at your own risk.


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.