External References

Mill comes bundled with a set of external Open Source libraries and projects.


OS-Lib is a simple, flexible, high-performance Scala interface to common OS filesystem and subprocess APIs.

Mill uses OS-Lib for all of its file system operations.


uPickle: a simple Scala JSON and Binary (MessagePack) serialization library

Mill uses uPickle to cache target output to disk as JSON, and to output JSON for third-party tools to consume.


Requests-Scala is a Scala port of the popular Python Requests HTTP client. Requests-Scala aims to provide the same API and user-experience as the original Requests: flexible, intuitive, and straightforward to use.

Mill bundles Requests for you to use to make HTTP requests.


MainArgs is a small, dependency-free library for command line argument parsing in Scala.

Mill uses MainArgs to handle argument parsing for `T.command`s that are run from the command line.


Coursier is the Scala application and artifact manager. Mill uses Coursier for all third-party artifact resolution and management in JVM languages (Scala, Java, etc.)