Nightly Versions of Scala

We regularly publish nightly versions of both Scala 3 and 2 so that users can preview and test the contents of upcoming releases.

Here’s how to find and use these versions.

General information on nightlies

Scala 3

Scala 3 nightly versions are published to https://repo.scala-lang.org. Historically, they used to be published to Maven Central. Old nightly versions of Scala 3 (all the way until 3.8.0-RC1-bin-20250822-658c8bd-NIGHTLY in August 2025) are still available there, as well as via https://repo.scala-lang.org.

If you know the full version number of the nightly you want to use, you can use it just like any other Scala 3 version.

There are a number of ways to get that version number, as listed below.

Scala 2

We informally refer to Scala 2 “nightly” versions, but technically it’s a misnomer. A so-called “nightly” is built for every merged PR in the Scala 2 repo.

Similarly to Scala 3 nightlies, they are available at https://repo.scala-lang.org.

How to use nightly versions

Scala CLI

Scala CLI is the official runner of the language and has nightlies available without any extra configuration. From Scala 3.5.0 and on it’s available under the scala command in Scala 3 installations. It can also be installed separately as scala-cli.

Note: The nightly repository is supported since Scala CLI v1.9.0 onwards (or scala installed with Scala 3.7.3 or newer).

You can run nightlies with commands such as:

scala -e 'println("Hello") -S 3.nightly
scala -e 'println("Hello") -S 3.3.nightly
scala -e 'println("Hello") -S 2.13.nightly
scala -e 'println("Hello") -S 2.nightly # same as 2.13.nightly
scala -e 'println("Hello") -S 2.12.nightly

The default command is repl (unless sources are passed, in which case it switches to run), but all the other scala-cli subcommands such as compile and run work, too. It also works with //> using directives in your script itself, for example:

//> using scala 3.nightly
//> using scala 3.3.nightly
//> using scala 2.nightly
//> using scala 2.13.nightly
//> using scala 2.12.nightly

See this scala-cli doc page for details.

Get it from the nightly website

A quick way to get that version number is to visit https://nightly.scala-lang.org and look in the upper left corner.

Check the repository, directly

Another way is to scrape the repository, as shown in this script: https://raw.githubusercontent.com/VirtusLab/community-build3/master/scripts/lastVersionNightly.sc

SBT

To use recent nightlies with SBT, adding the appropriate resolver to the build configuration is necessary.

ThisBuild / scalaVersion := "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
ThisBuild / resolvers += Resolver.scalaNightlyRepository
lazy val root = (project in file("."))
  .settings(name := "sbt-with-scala-nightlies")

Also note that SBT 1.11.5 or newer is necessary.

Mill

To use recent nightlies with Mill, a custom resolver for the initial bootstrap of the build is needed. Here’s an example build.mill file:

package build
import mill.*
import mill.api.*
import scalalib.*

def scalaNightlyRepo = "https://repo.scala-lang.org/artifactory/maven-nightlies"

object project extends ScalaModule {
  def jvmWorker = ModuleRef(CustomJvmWorkerModule)
  override def scalaVersion = "3.8.0-RC1-bin-20250916-eb1bb73-NIGHTLY"
  override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
}

object CustomJvmWorkerModule extends JvmWorkerModule, CoursierModule {
  override def repositories = Task { super.repositories() ++ Seq(scalaNightlyRepo)}
}

Note how the custom JvmWorkerModule is necessary with the added repository. It is not enough to just define it as a repository for the module dependencies.

Also note that Mill 1.0.5 or newer is necessary for this.