Scala Extensions

Open-source Scala projects categorized as Extensions
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Top 23 Scala Extension Projects

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Extensions

  1. cats

    Lightweight, modular, and extensible library for functional programming.

    Project mention: What F# Knows About Functors and What Comes Next | dev.to | 2025-12-26

    As an F# developer, if you want to play with a Functor, you usually have to name your dog yourself (or your cat — but that would make the metaphor silly).

  2. SaaSHub

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  3. Scalaz

    Principled Functional Programming in Scala

  4. Shapeless

    Generic programming for Scala

    Project mention: Three Stabs at a Typed Schema DSL in Kotlin | dev.to | 2026-05-12

    I built the N×M expansion with a KSP processor that generated a trait accessor per position-trait combo, and it compiled. But the abstraction leaked: every call site had to import the right extensions for the traits it read, the parameterized-instances pattern still had no clean read, and the whole thing felt like a hack. Languages with higher-kinded or dependent types make this natural (shapeless is the closest analogue on the JVM), but that's not exactly mainstream territory. Without those features you're encoding a record with positional bookkeeping. I cut it.

  5. Twitter Util

    Wonderful reusable code from Twitter

  6. Ammonite-Ops

    Scala Scripting

  7. refined

    Refinement types for Scala

    Project mention: Stop Writing if-checks: Refinement Types in Java 8+ | dev.to | 2026-03-16

    Scala's refined uses compile-time macros to verify literal values at compilation. java-refined operates at runtime because Java lacks macro support. The tradeoff: Scala refined catches errors at compile time for literals, while java-refined catches errors at construction time for all values (including dynamic input). Both encode the constraint in the type system.

  8. Monocle

    Optics library for Scala

  9. better-files

    Simple, safe and intuitive Scala I/O

  10. Chimney

    Scala library for boilerplate-free, type-safe data transformations

  11. Enumeratum

    A type-safe, reflection-free, powerful enumeration implementation for Scala with exhaustive pattern match warnings and helpful integrations.

  12. Scala Async

    An asynchronous programming facility for Scala

  13. scala.meta

    Library to read, analyze, transform and generate Scala programs

  14. Cassovary

    Cassovary is a simple big graph processing library for the JVM

  15. Simulacrum

    First class syntax support for type classes in Scala

  16. Scala-Logging

    Convenient and performant logging library for Scala wrapping SLF4J.

  17. n-scala

    A new Scala wrapper for Joda Time based on scala-time

  18. Quicklens

    Modify deeply nested case class fields

    Project mention: Scala 3 slowed us down? | news.ycombinator.com | 2025-12-07

    The library that caused breakage for the OP is a good example: https://github.com/softwaremill/quicklens

  19. Freestyle

    A cohesive & pragmatic framework of FP centric Scala libraries

  20. Eff

    Eff monad for cats - https://atnos-org.github.io/eff

  21. Scala Graph

    Graph for Scala is intended to provide basic graph functionality seamlessly fitting into the Scala Collection Library. Like the well known members of scala.collection, Graph for Scala is an in-memory graph library aiming at editing and traversing graphs, finding cycles etc. in a user-friendly way.

  22. scribe

    The fastest logging library in the world. Built from scratch in Scala and programmatically configurable. (by outr)

  23. LArray

    Large off-heap arrays and mmap files for Scala and Java

  24. Hamsters

    A mini Scala utility library

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).

Scala Extensions discussion

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Scala Extensions related posts

  • Stop Writing if-checks: Refinement Types in Java 8+

    3 projects | dev.to | 16 Mar 2026

  • What F# Knows About Functors and What Comes Next

    2 projects | dev.to | 26 Dec 2025

  • Make Invalid States Unrepresentable

    2 projects | dev.to | 2 Feb 2024

  • Engenharia de Dados com Scala: aprenda a fazer webscraping dos filmes mais assistidos da Netflix em cada país

    5 projects | dev.to | 27 Nov 2023

  • Chimney 0.8.0 (stable) released

    1 project | /r/scala | 13 Oct 2023

  • RFC: A Path Forward for Ammonite REPL and Scripts in 2023 and Beyond

    1 project | /r/scala | 3 Sep 2023

  • Chimney 0.8.0-M1 with the initial support for Scala 3

    1 project | /r/scala | 5 Aug 2023
  • A note from our sponsor - SaaSHub
    www.saashub.com | 6 Jun 2026
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Index

What are some of the best open-source Extension projects in Scala? This list will help you:

# Project Stars
1 cats 5,445
2 Scalaz 4,671
3 Shapeless 3,406
4 Twitter Util 2,724
5 Ammonite-Ops 2,634
6 refined 1,731
7 Monocle 1,697
8 better-files 1,474
9 Chimney 1,250
10 Enumeratum 1,221
11 Scala Async 1,161
12 scala.meta 1,154
13 Cassovary 1,053
14 Simulacrum 930
15 Scala-Logging 926
16 n-scala 867
17 Quicklens 849
18 Freestyle 615
19 Eff 589
20 Scala Graph 576
21 scribe 551
22 LArray 406
23 Hamsters 287

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