Browse free open source Scala Libraries and projects below. Use the toggles on the left to filter open source Scala Libraries by OS, license, language, programming language, and project status.

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  • 1
    tapir

    tapir

    Declarative, type-safe web endpoints library

    Declarative, type-safe web endpoints library. With tapir, you can describe HTTP API endpoints as immutable Scala values. Each endpoint can contain a number of input and output parameters. Compile-time guarantees, develop-time completions, read-time information. Separate the shape of the endpoint (the "what"), from the server logic (the "how"). Generate documentation from endpoint descriptions. Leverage the metadata to report rich metrics and tracing information. Re-use common endpoint definitions, as well as individual inputs/outputs. Library, not a framework, integrates with your stack. Is your company already using tapir? We're continually expanding the "adopters" section in the documentation; the more the merrier! It would be great to feature your company's logo, but in order to do that, we'll need to write permission to avoid any legal misunderstandings.
    Downloads: 8 This Week
    Last Update:
    See Project
  • 2
    Alpakka Kafka

    Alpakka Kafka

    Alpakka is a Reactive Enterprise Integration library for Java

    The Alpakka project is an open source initiative to implement stream-aware and reactive integration pipelines for Java and Scala. It is built on top of Akka Streams and has been designed from the ground up to understand streaming natively and provide a DSL for reactive and stream-oriented programming, with built-in support for backpressure. Akka Streams is a Reactive Stream and JDK 9+ java.util.concurrent.Flow-compliant implementation and therefore fully interoperable with other implementations. As Kafka’s client protocol negotiates the version to use with the Kafka broker, you may use a Kafka client version that is different than the Kafka broker’s version.
    Downloads: 7 This Week
    Last Update:
    See Project
  • 3
    Skunk

    Skunk

    A data access library for Scala + Postgres

    Skunk is a Postgres library for Scala. Skunk is powered by cats, cats-effect, scodec, and fs2. Skunk is purely functional, non-blocking, and provides a tagless-final API. Skunk gives very good error messages. Skunk embraces the Scala Code of Conduct. Skunk is pre-release software! Code and documentation are under active development! Skunk is published for Scala 2.12/2.13/3.1 and can be included in your project.Query and Command types are usually inferrable, but specifying a type ensures that the chosen encoders and decoders are consistent with the expected input and output Scala types. Postgres provides a protocol for execution of simple queries, returning all rows at once (Skunk returns them as a list).
    Downloads: 6 This Week
    Last Update:
    See Project
  • 4
    Slick database

    Slick database

    Slick (Scala Language Integrated Connection Kit) is a modern database

    Slick is a modern database query and access library for Scala. It allows you to work with stored data almost as if you were using Scala collections while at the same time giving you full control over when a database access happens and which data is transferred. You can write your database queries in Scala instead of SQL, thus profiting from the static checking, compile-time safety and compositionality of Scala. Slick features an extensible query compiler which can generate code for different backends. It allows you to work with relational databases almost as if you were using Scala collections, while at the same time giving you full control over when a database access happens and what data is transferred. By writing your queries in Scala you can benefit from the static type checking, compile-time safety, and compositionality of Scala, while retaining the ability to drop down to raw SQL where needed for custom or advanced database features.
    Downloads: 4 This Week
    Last Update:
    See Project
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  • 5
    FS2

    FS2

    Compositional, streaming I/O library for Scala

    FS2 (“Functional Streams for Scala”) is a purely functional, effectful abstraction for stream processing on the JVM. Built on Cats Effect, it enables compositional resource-safe streaming workflows with robust error handling, back-pressure, pull/push semantics, and support for concurrent and interruptible pipelines.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 6
    Kamon Telemetry

    Kamon Telemetry

    Distributed Tracing, Metrics and Context Propagation for applications

    Kamon Telemetry is a set of libraries for instrumenting applications running on the JVM. With Kamon Telemetry you can collect metrics, propagate context across threads and services, and get distributed traces automatically. The best way to get started is by following our installation guides and taking it from there. Have fun with Kamon. Monitor your backend applications, fix performance issues, and get alerted when problems happen. All without being a monitoring expert. Everybody starts monitoring with logs because they are there by default. Just connect to your server and start tailing. But logs have a hard time showing you the overall response times for your application, or whether certain calls to the database are happening in sequence or parallel (among a million other things).
    Downloads: 3 This Week
    Last Update:
    See Project
  • 7
    Refined

    Refined

    Refinement types for Scala

    Refined is a Scala library that enhances types with compile-time constraints using predicate-style refinement types. It allows embedding validation logic into types like Refined[Int, Positive], ensuring invalid values are rejected at compile or runtime, thereby increasing safety and reducing boilerplate in domain modeling.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 8
    Sangria

    Sangria

    Scala GraphQL implementation

    Sangria is a Scala GraphQL implementation. It is an example of GraphQL server written with Play framework and Sangria. It also serves as a playground, where you can interactively execute GraphQL queries and play with some examples. If you want to use sangria with a react-relay framework, then you also may be interested in sangria-relay. Sangria is a spec-compliant GraphQL implementation, so it works out of the box with Apollo, Relay, GraphiQL and other GraphQL tools and libraries. Since GraphQL has a type system, the server defines a schema that the client can query using the introspection API. This provides the client with a set of possibilities. After the client got this information and decided which parts of the data it needs, it is able to describe its data requirements in form of a GraphQL query. An important aspect of GraphQL is that it’s completely backend agnostic.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 9
    Scala 2

    Scala 2

    Scala 2 compiler and standard library

    Scala combines object-oriented and functional programming in one concise, high-level language. Scala's static types help avoid bugs in complex applications, and its JVM and JavaScript runtimes let you build high-performance systems with easy access to huge ecosystems of libraries. Scastie is Scala + sbt in your browser! You can use any version of Scala, or even alternate backends such as Dotty, Scala.js, Scala Native, and Typelevel Scala. You can use any published library. You can save and share Scala programs/builds with anybody. The Scala Library Index (or Scaladex) is a representation of a map of all published Scala libraries. With Scaladex, a developer can now query more than 175,000 releases of Scala libraries. Scaladex is officially supported by Scala Center. In Scala, functions are values, and can be defined as anonymous functions with a concise syntax. In Scala, case classes are used to represent structural data types.
    Downloads: 3 This Week
    Last Update:
    See Project
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  • 10
    Shapeless

    Shapeless

    Generic programming for Scala

    Shapeless is a powerful generic programming library for Scala, enabling compile-time abstraction and manipulation of types. It provides features such as HLists (heterogenous lists), generic derivation of type class instances, dependent types, and polymorphic functions—allowing developers to write boilerplate-free, type-safe code.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 11
    Spire

    Spire

    Powerful new number types and numeric abstractions for Scala

    Spire is a numeric and algebraic library for Scala, offering type-safe, generic, and high-precision arithmetic. It introduces abstractions like Rings, Fields, and Rationals and supports specialized number types (e.g. Rational, Complex, Interval), macros, and seamless integration with Cats for abstract numeric programming.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 12
    Twitter Util

    Twitter Util

    Wonderful reusable code from Twitter

    Twitter Util is a collection of utility libraries used at Twitter, covering concurrency (Futures, Promises), timing, caching, I/O helpers, validation, stats collection, and Scala–Java interoperability. Designed for reliability and efficiency in high-scale systems.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 13
    scalajs-react

    scalajs-react

    Facebook's React on Scala.JS

    Scala.js React wraps Facebook React for Scala.js with a strong emphasis on type safety and functional idioms. It provides a typed virtual DOM interface, reusable components, hooks, and utilities for routing, testing, SSR, and performance profiling, all aligned with Cats, Cats Effect, and Monocle ecosystems.
    Downloads: 3 This Week
    Last Update:
    See Project
  • 14
    Algebird

    Algebird

    Abstract Algebra for Scala

    Algebird is Twitter’s Apache‑licensed Scala library providing abstract algebra data structures and algorithms, especially for online/streaming aggregation. It includes Monoid, Approximate, HyperLogLog, CMS, BloomFilter, Min/Max, Averaged Value types, supporting efficient distributed aggregation and approximate analytics.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 15
    Monix

    Monix

    Asynchronous, Reactive Programming for Scala and Scala.js

    Monix is a high-performance, reactive, and asynchronous programming library for Scala and Scala.js. Built as a Typelevel project, it provides advanced abstractions like Task, Observable, Iterant, and Coeval, enabling compositional, back-pressure‑aware event-driven systems that integrate cleanly with Cats Effect and Reactive Streams.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 16
    Monocle

    Monocle

    Optics library for Scala

    Monocle is a pure functional, optics library for Scala providing immutable data access and transformation tools — including Lens, Prism, Iso, Optional, and Traversal. It enables composable, declarative modifications of deeply nested immutable structures in a concise and type-safe fashion.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 17
    SageMaker Spark

    SageMaker Spark

    A Spark library for Amazon SageMaker

    SageMaker Spark is an open-source Spark library for Amazon SageMaker. With SageMaker Spark you construct Spark ML Pipelines using Amazon SageMaker stages. These pipelines interleave native Spark ML stages and stages that interact with SageMaker training and model hosting. With SageMaker Spark, you can train on Amazon SageMaker from Spark DataFrames using Amazon-provided ML algorithms like K-Means clustering or XGBoost, and make predictions on DataFrames against SageMaker endpoints hosting your trained models, and, if you have your own ML algorithms built into SageMaker compatible Docker containers, you can use SageMaker Spark to train and infer on DataFrames with your own algorithms -- all at Spark scale. SageMaker Spark depends on hadoop-aws-2.8.1. To run Spark applications that depend on SageMaker Spark, you need to build Spark with Hadoop 2.8. However, if you are running Spark applications on EMR, you can use Spark built with Hadoop 2.7.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 18
    Synapse Machine Learning

    Synapse Machine Learning

    Simple and distributed Machine Learning

    SynapseML (previously MMLSpark) is an open source library to simplify the creation of scalable machine learning pipelines. SynapseML builds on Apache Spark and SparkML to enable new kinds of machine learning, analytics, and model deployment workflows. SynapseML adds many deep learning and data science tools to the Spark ecosystem, including seamless integration of Spark Machine Learning pipelines with the Open Neural Network Exchange (ONNX), LightGBM, The Cognitive Services, Vowpal Wabbit, and OpenCV. These tools enable powerful and highly-scalable predictive and analytical models for a variety of data sources. SynapseML also brings new networking capabilities to the Spark Ecosystem. With the HTTP on Spark project, users can embed any web service into their SparkML models. For production-grade deployment, the Spark Serving project enables high throughput, sub-millisecond latency web services, backed by your Spark cluster.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 19
    ZIO

    ZIO

    A type-safe, composable library for async and concurrent programming

    ZIO is a purely functional, type-safe Scala library that provides an Effect (ZIO[R,E,A]) abstraction for asynchronous, concurrent programming. It offers resource safety, fiber-based concurrency, strong error handling, and deterministic testing—all with zero external dependencies. Ideal for building scalable backend systems with compositional architecture.
    Downloads: 2 This Week
    Last Update:
    See Project
  • 20
    atto

    atto

    Friendly little parsers

    Atto is a compact, pure-functional, incremental text parsing library for Scala. It offers a non-invasive API using familiar abstractions, making it a principled tool for everyday parsing tasks in functional programming.​
    Downloads: 2 This Week
    Last Update:
    See Project
  • 21
    Binding.scala

    Binding.scala

    Reactive data-binding for Scala

    Binding.scala is a data-binding library for Scala, running on both JVM and Scala.js. Binding.scala can be used as the basis of UI frameworks, however latest Binding.scala 12.x does not contain any build-in UI frameworks anymore. For creating reactive HTML UI, you may want to check out html.scala, which is a UI framework based on Binding.scala, and it is also the successor of the previously built-in dom library. See also React / Binding.scala / html.scala Interoperability for using existing React components with Binding.scala. Regular HTML does not compile unless developers manually replace class and for attributes to className and htmlFor, and manually convert inline styles from CSS syntax to JSON syntax.
    Downloads: 1 This Week
    Last Update:
    See Project
  • 22
    Caliban

    Caliban

    Functional GraphQL library for Scala

    Caliban is a purely functional library for building GraphQL servers and clients in Scala. The design principles behind the library are the following. Minimal amount of boilerplate: no need to manually define a schema for every type in your API. Pure interface: errors and effects are returned explicitly (no exceptions thrown), all returned types are referentially transparent (no Future). Clean separation between schema definition and implementation: schema is defined and validated at compile time using Scala standard types, resolver (RootResolver) is a simple value provided at runtime. All interfaces are pure and types are referentially transparent. Schemas are type safe and derived at compile time. No need to manually define a schema for every type in your API. Let the compiler do the boring work. Out-of-the-box support for major HTTP server libraries, effect types, Json libraries and more.
    Downloads: 1 This Week
    Last Update:
    See Project
  • 23
    Cats

    Cats

    Lightweight, modular, extensible library for functional programming

    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. Scala supports both object-oriented and functional programming, and this is reflected in the hybrid approach of the standard library. Cats strives to provide functional programming abstractions that are core, binary compatible, modular, approachable and efficient. A broader goal of Cats is to provide a foundation for an ecosystem of pure, typeful libraries to support functional programming in Scala applications. Cats strives to provide a solid and stable foundation for an ecosystem of FP libraries. Thus, we treat backward binary compatibility maintenance with a high priority. In semantic versioning, backward breaking change is only allowed between major versions.
    Downloads: 1 This Week
    Last Update:
    See Project
  • 24

    Waterloo

    Java-based scientific graphics

    Java-based scientific graphics with support for Java, Groovy, MATLAB, Python, the R statistical environment, Scala and SciLab.
    Downloads: 4 This Week
    Last Update:
    See Project
  • 25
    Scalaffinity
    Scalaffinity is a library providing a core of functionalities for any social networking web site extracting and leveraging collective intelligence. Scalaffinity is built using Scala, Spring, JPA+Hibernate(Search)+EHCache, JUnit+DBUnit, Maven...
    Downloads: 1 This Week
    Last Update:
    See Project
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