Installation

Requirements

• Scala 3.9 (LTS) or later. uni's artifacts are compiled with Scala 3.9, and older compilers cannot read their TASTy.
• sbt 1.9+ or sbt 2.x

Adding Dependencies

Add uni to your build.sbt:

// Core utilities (object wiring, logging, JSON, HTTP, Rx, etc.)
libraryDependencies += "org.wvlet.uni" %% "uni" % "2026.1.22"

HTTP Server on the JVM

To run an HTTP server on the JVM, add the Netty-based server module (it pulls in uni transitively):

// Netty-based HTTP server (JVM only)
libraryDependencies += "org.wvlet.uni" %% "uni-netty" % "2026.1.22"

See the REST Server guide for usage. On Scala.js and Scala Native, the HTTP server backends (NodeServer / NativeServer) are included in uni itself — no extra module is needed.

Testing Framework

Add UniTest as a test dependency and register its test framework:

libraryDependencies += "org.wvlet.uni" %% "uni-test" % "2026.1.22" % Test
testFrameworks += new TestFramework("wvlet.uni.test.Framework")

Cross-Platform Projects

For Scala.js or Scala Native projects on sbt 1.x, use %%%:

// Scala.js / Scala Native (sbt 1.x)
libraryDependencies += "org.wvlet.uni" %%% "uni" % "2026.1.22"
libraryDependencies += "org.wvlet.uni" %%% "uni-test" % "2026.1.22" % Test

On sbt 2.x, %% resolves the platform-specific artifact for all platforms, so %%% is not needed.

Scala Native and libcurl

No system libraries are needed to build a Scala Native binary against uni. Only reaching for the HTTP client pulls in libcurl, which must then be present as a shared library — see Linking libcurl on Scala Native.

Imports

Common imports for getting started:

// Object wiring
import wvlet.uni.design.Design

// Logging
import wvlet.uni.log.{LogSupport, Logger, LogLevel}

// JSON
import wvlet.uni.json.JSON

// HTTP
import wvlet.uni.http.{Http, HttpRequest, HttpResponse}

// Reactive streams
import wvlet.uni.rx.Rx

// Control flow
import wvlet.uni.control.{Retry, CircuitBreaker, Resource}

Verifying Installation

Create a simple test to verify the installation:

import wvlet.uni.log.LogSupport

object Main extends App with LogSupport:
  info("uni is working!")

Run with:

sbt run

You should see log output with your message.

IDE Support

uni works with all major Scala IDEs:

• IntelliJ IDEA with Scala plugin
• VS Code with Metals
• Neovim with Metals

The library uses standard Scala 3 features, so IDE support is seamless.