Mill is a fast JVM build tool that supports Java, Scala, Kotlin and many other languages. 3-6x faster than Maven or Gradle for common workflows, Mill aims to make your project’s build process performant, maintainable, and flexible

Simple, expressive, and safe UI library for Scala.js

Scala macros for compile-time generation of safe and ultra-fast JSON codecs + circe booster

Simple & Efficient data access for Scala and Scala.js

Describe HTTP endpoints in Scala and derive clients, servers, and documentation

Elm-inspired Scala UI library.

https://disneystreaming.github.io/smithy4s/

property based testing library for Scala

Using the latest technology in the Scala ecosystem, Boilerplay is a reactive web application built on Play Framework, ScalaJS, Silhouette, Sangria/GraphQL, and PostgreSQL. It provides a good starting point for whatever you want to build.

State propagation and event streams with mandatory ownership and no glitches

Cross-platform compilation support for sbt.

Typescript to Scala.js converter

A GitHub API wrapper written in Scala

Next generation user interface and application development in Scala and Scala.js for web, mobile, and desktop.

experimental CPS transformer for dotty

Scala FP configuration library with a focus on runtime clarity

RTree2D is a 2D immutable R-tree for ultra-fast nearest and intersection queries in plane and spherical coordinates

Pure, reactive UI library for Scala.js

Scala configuration library supporting HOCON for Scala, Java, Scala.js, and Scala Native