Cats is a library which provides abstractions for functional programming in the Scala programming language.

Cats Effect is a high-performance, asynchronous, composable framework for building real-world applications in a purely functional style within the Typelevel ecosystem.

Core classes for Circe, a JSON library for Scala developed with a focus on performance.

Functional, effectful, concurrent streams for Scala

Support for IO operations in the fs2 ecosystem

Cats laws

catsJVM

Cats Free

Core http4s library for servers and clients

log4cats-core

core