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zio/zio

ZIO — A type-safe, composable library for async and concurrent programming in Scala
Source code at GitHub https://zio.dev
zio/zio.json
{
  "createdAt": "2018-05-19T16:40:37Z",
  "defaultBranch": "series/2.x",
  "description": "ZIO — A type-safe, composable library for async and concurrent programming in Scala",
  "fullName": "zio/zio",
  "homepage": "https://zio.dev",
  "language": "Scala",
  "name": "zio",
  "pushedAt": "2025-11-25T11:26:52Z",
  "stargazersCount": 4311,
  "topics": [
    "asynchronicity",
    "asynchronous",
    "asynchronous-programming",
    "concurrency",
    "concurrent",
    "concurrent-data-structure",
    "concurrent-programming",
    "effects",
    "functional-programming",
    "promises",
    "queues",
    "scala",
    "stm",
    "streams",
    "zio"
  ],
  "updatedAt": "2025-11-27T05:57:52Z",
  "url": "https://github.com/zio/zio"
}

![ZIO Logo]!(./ZIO.png)

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[![Project stage][Badge-Stage]][Badge-Stage-Page]![CI][Badge-CI][Maven Central Version][Link-SonatypeReleases][![Snapshot Artifacts][Badge-SonatypeSnapshots]][Link-SonatypeSnapshots][![Average time to resolve an issue][Badge-IsItMaintained]][Link-IsItMaintained]
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[Scaladoc][Link-Scaladoc][![Badge-Scaladex-page]][Link-Scaladex-page][![Badge-Discord]][Link-Discord][![Badge-Twitter]][Link-Twitter]Gitpod ready-to-codeGurubase

Welcome to ZIO

Section titled “Welcome to ZIO”

ZIO is a zero-dependency Scala library for asynchronous and concurrent programming.

Powered by highly-scalable, non-blocking fibers that never waste or leak resources, ZIO lets you build scalable, resilient, and reactive applications that meet the needs of your business.

  • High-performance. Build scalable applications with minimal runtime overhead.
  • Type-safe. Use the full power of the Scala compiler to catch bugs at compile time.
  • Concurrent. Easily build concurrent apps without deadlocks, race conditions, or complexity.
  • Asynchronous. Write sequential code that looks the same whether it’s asynchronous or synchronous.
  • Resource-safe. Build apps that never leak resources (including threads!), even when they fail.
  • Testable. Inject test services into your app for fast, deterministic, and type-safe testing.
  • Resilient. Build apps that never lose errors, and which respond to failure locally and flexibly.
  • Functional. Rapidly compose solutions to complex problems from simple building blocks.

To learn more about ZIO, see the following references:

Adopters

Section titled “Adopters”

Following is a partial list of companies happily using ZIO in production to craft concurrent applications.

Want to see your company here? Submit a PR!

Sponsors

Section titled “Sponsors”

[![Ziverge][Image-Ziverge]][Link-Ziverge]

[Ziverge][Link-Ziverge] is a leading contributor to ZIO.

[![Septimal Mind][Image-SeptimalMind]][Link-SeptimalMind]

[Septimal Mind][Link-SeptimalMind] sponsors work on ZIO Tracing and continuous maintenance.

[![YourKit][Image-YourKit]][Link-YourKit]

[YourKit][Link-YourKit] generously provides use of their monitoring and profiling tools to maximize the performance of ZIO applications.

Learn More on the ZIO Homepage

Section titled “Learn More on the ZIO Homepage”

Code of Conduct

Section titled “Code of Conduct”

See the [Code of Conduct]!(docs/code-of-conduct.md)

Support

Section titled “Support”

Come chat with us on [![Badge-Discord]][Link-Discord].

Section titled “Legal”

Copyright 2017 - 2024 John A. De Goes and the ZIO Contributors. All rights reserved.

[Link-Codecov] !: https://codecov.io/gh/zio/zio?branch=master “Codecov” [Link-IsItMaintained] !: http://isitmaintained.com/project/zio/zio “Average time to resolve an issue” [Link-Scaladoc] !: https://javadoc.io/doc/dev.zio/zio_3/latest/zio/index.html [Link-Scaladex-page] !: https://index.scala-lang.org/zio/zio/zio “Scaladex” [Link-SonatypeReleases] !: https://oss.sonatype.org/content/repositories/releases/dev/zio/zio_3/ “Sonatype Releases” [Link-SonatypeSnapshots] !: https://oss.sonatype.org/content/repositories/snapshots/dev/zio/zio_3/ “Sonatype Snapshots” [Link-Ziverge] !: https://ziverge.com “Ziverge” [Link-Scalac] !: https://scalac.io “Scalac” [Link-SeptimalMind] !: https://7mind.io “Septimal Mind” [Link-YourKit] !: https://www.yourkit.com “YourKit” [Link-Discord] !: https://discord.gg/2ccFBr4 “Discord” [Link-Twitter] !: https://twitter.com/zioscala

[Badge-CI] !: https://github.com/zio/zio/workflows/CI/badge.svg [Badge-Codecov] !: https://codecov.io/gh/zio/zio/coverage.svg?branch=master “Codecov” [Badge-IsItMaintained] !: http://isitmaintained.com/badge/resolution/zio/zio.svg “Average time to resolve an issue” [Badge-Scaladex-page] !: https://index.scala-lang.org/zio/zio/zio/latest.svg “Scaladex” [Badge-SonatypeReleases] !: https://img.shields.io/nexus/r/https/oss.sonatype.org/dev.zio/zio_3.svg “Sonatype Releases” [Badge-SonatypeSnapshots] !: https://img.shields.io/nexus/s/https/oss.sonatype.org/dev.zio/zio_3.svg “Sonatype Snapshots” [Badge-Discord] !: https://img.shields.io/discord/629491597070827530?logo=discord “chat on discord” [Badge-Twitter] !: https://img.shields.io/twitter/follow/zioscala.svg?style=plastic&label=follow&logo=twitter [Badge-Stage] !: https://img.shields.io/badge/Project%20Stage-Production%20Ready-brightgreen.svg [Badge-Stage-Page] !: https://github.com/zio/zio/wiki/Project-Stages

[Image-Ziverge] !: ./website/static/img/ziverge.png “Ziverge” [Image-SeptimalMind] !: ./website/static/img/septimal_mind.svg “Septimal Mind” [Image-YourKit] !: ./website/static/img/yourkit.png “YourKit”