ZIO VS cats

Compare ZIO vs cats and see what are their differences.


Lightweight, modular, and extensible library for functional programming. (by typelevel)
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ZIO cats
48 33
3,628 4,803
1.7% 0.7%
9.9 9.7
7 days ago 5 days ago
Scala Scala
Apache License 2.0 GNU General Public License v3.0 or later
The number of mentions indicates the total number of mentions that we've tracked plus the number of user suggested alternatives.
Stars - the number of stars that a project has on GitHub. Growth - month over month growth in stars.
Activity is a relative number indicating how actively a project is being developed. Recent commits have higher weight than older ones.
For example, an activity of 9.0 indicates that a project is amongst the top 10% of the most actively developed projects that we are tracking.


Posts with mentions or reviews of ZIO. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2022-11-16.
  • What’s so great about functional programming anyway?
    8 projects | news.ycombinator.com | 16 Nov 2022
    > It's a weakness of functional programming, not the language.

    I would strongly object this.

    Have you seen ZIO?


  • Switching career from F# to scala
    2 projects | reddit.com/r/scala | 24 Oct 2022
    But overall, I'm happier with Scala. It has not one, but two lively FP communities. I recommend that you pick one of them: ZIO or TypeLevel (Cats Effect, fs2, http4s, ...). To some extent, you can mix TypeLevel libraries in ZIO projects.
  • New to Scala;
    8 projects | reddit.com/r/scala | 14 Oct 2022
  • Next Steps for Rust in the Kernel
    8 projects | news.ycombinator.com | 21 Sep 2022
    I think "better Haskell on JVM" (in contrast to "worse Haskell") is a good identity for Scala to have. (Please note that this is an intentional hyperbole.)

    Of course, there are areas where Haskell is stronger than Scala (hint: modularity, crucial for good Software Engineering, is not one of them). And Scala has its own way of doing things, so just imitating Haskell won't work well.

    Examples of this "better Haskell" are https://typelevel.org/cats-effect/ and https://zio.dev/ .

    All together, Scala may be a better choice for you if you want to do Pure Functional Programming. And is definitely less risky (runs on JVM, Java libraries interop, IntelliJ, easy debugging, etc...).

    None of the other languages you mentioned are viable in this sense (if also you want a powerful type system, which rules out Clojure).

    I agree that Rust's identity is pretty clear: a modern language for use cases where only C or C++ could have been used before.

  • Java 19 Is Out
    4 projects | news.ycombinator.com | 20 Sep 2022
    I would use Scala. I like FP and Scala comes with some awesome libraries for concurrent/async programming like Cats Effect or ZIO. Good choice for creating modern style micro-services to be run in the cloud (or even macro-services, Scala has a powerful module system, so it's made to handle large codebases).



    The language, the community and customs are great. You don't have to worry about nulls, things are immutable by default, domain modelling with ADTs and patter matching is pure joy.

    The tooling available is from good to great and Scala is big enough that there are good libraries for typical if not vast majority of stuff and Java libs as a reliable fallback.

  • Scala Isn't Fun Anymore
    9 projects | news.ycombinator.com | 13 Sep 2022
    I actually think Scala is in the best position it's ever been.

    There is a commitment to making the language simpler, easier and cleaner.

    On the backend, ZIO [1] is the best concurrency library on any platform. On the frontend you have really interesting Scala.js projects like Laminar [2].

    The biggest issue really is the tooling. SBT is simply awful.

    [1] https://zio.dev

  • A Python-compatible statically typed language erg-lang/erg
    27 projects | news.ycombinator.com | 13 Aug 2022
  • Ask HN: Any alternative to Java (OOP) which has the same ecosystem?
    5 projects | news.ycombinator.com | 11 Jul 2022
    Scala? With some help from additional libs such as Zio (https://zio.dev/) it allows you to write production quality programs like you would in Haskell on top of the JVM quite quickly...
  • Cats vs ZIO
    2 projects | reddit.com/r/scala | 10 Jul 2022
  • ZIO 2.0 Released
    2 projects | reddit.com/r/scala | 24 Jun 2022
    If you have experience using Future, and are looking for an introduction to "Why ZIO?", then you might enjoy my talk, Upgrade Your Future. The talk contains a bit of getting started material, and you can keep an eye on zio.dev for more tutorials geared at users of Future and Akka.


Posts with mentions or reviews of cats. We have used some of these posts to build our list of alternatives and similar projects. The last one was on 2022-10-28.
  • Which functional programming language should I learn?
    5 projects | reddit.com/r/functionalprogramming | 28 Oct 2022
    3) Finally, Scala 3 + cats is a great middle ground. It's a great language to teach and learn FP, even if you learn by yourself, without support from other people. There are lots of materials and even if you get stuck with a concept, you can still implement it using what you knew before.
  • Should I learn it? If yes then which?
    2 projects | reddit.com/r/scala | 28 Oct 2022
  • Should I Move From PHP to Node/Express?
    13 projects | reddit.com/r/node | 13 Oct 2022
    On the contrary, switching to the functional mindset, with something like Typelevel Scala3 and respective cats and cats-effect fs2 frameworks, helps to rethink a lot of designs and development approaches.
  • Question about some advanced types
    3 projects | reddit.com/r/scala | 5 Sep 2022
    You want Kernmantle, which quite honestly shouldn't be hard to implement around Cats and cats-effect. In particular, although Kernmantle doesn't require the use of the Arrow typeclass, there happen to be Arrow (actually ArrowChoice) instances for both Function1 from the standard library and Kleisli from Cats itself, given a Monad instance for the Kleilsi's F[_] type parameter. In other words, we should be able to port Kernmantle from Haskell to Scala (with the Typelevel ecosystem) and instantly be able to use pretty much anything else from the Typelevel ecosystem, or wrapped with it, in our workflow graphs. Pure functions, monadic functions, applicative functions, GADTs with hand-written interpreters, any of it. I think this would be eminently worth doing.
  • Thanks to Rust Kotlin makes me like JVM
    4 projects | reddit.com/r/rust | 28 Aug 2022
    If you want to use simple straightforward scala https://www.lihaoyi.com/ did a lot for the ecosystem creating simple libraries not forcing fp. For fp look at https://typelevel.org/cats/ though I won't recommend diving too deep in the rabbit hole, I know lots of people swear by it, but I think it just overcomplicates code for few tangible benefits (code being pure and guaranteed free of side effects means little to me). It's is fun to get things working though, much less maintaining/migrating old code)
  • A Python-compatible statically typed language erg-lang/erg
    27 projects | news.ycombinator.com | 13 Aug 2022
  • Typeclasses explained in Java
    3 projects | dev.to | 27 Jul 2022
    If I managed to gain you interest you can take a look at one of the following libraries like cats, scalaz for scala and vavr for java which contain type class definitions and implementations for common types.
  • Junior developer looking for a Haskell codebase to work on and a mentor to help me
    6 projects | reddit.com/r/haskell | 2 Jun 2022
    Scala is like a cross between Java and Haskell. Scala has a notation for monads similar to Haskell's `do ...` notation. It has libraries like (cats)[http://typelevel.org/cats/] (the name "cats" is short for "category theory") for functional programming. It has immutable classes with copy constructors similar to Haskell's records. Both languages have implicit parameters. I like immutability and strong type systems.
  • Trying to decide on Scala or Kotlin
    7 projects | reddit.com/r/scala | 20 Mar 2022
    Cats is a library which provides abstractions for functional programming in the Scala programming language. The name is a playful shortening of the word category. https://typelevel.org/cats/
  • Oh no! te cruzaste con un gato de IT ¿le pedís que te enseñe python o java?
    2 projects | reddit.com/r/argentina | 10 Mar 2022
    Obviamente que teoria de categorias https://typelevel.org/cats/

What are some alternatives?

When comparing ZIO and cats you can also consider the following projects:

Shapeless - Generic programming for Scala

cats-effect - The pure asynchronous runtime for Scala

Scalaz - Principled Functional Programming in Scala

Monix - Asynchronous, Reactive Programming for Scala and Scala.js.

Http4s - A minimal, idiomatic Scala interface for HTTP

fs2-kafka - Functional Kafka Streams for Scala

Vert.x - Vert.x is a tool-kit for building reactive applications on the JVM

Scala.Rx - An experimental library for Functional Reactive Programming in Scala

Reactor-Scala-Extensions - A scala extension for Project Reactor's Flux and Mono

RxScala - RxScala – Reactive Extensions for Scala – a library for composing asynchronous and event-based programs using observable sequences

Scala Async - An asynchronous programming facility for Scala

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