Getting Started

Getting started with Flix is straightforward. All you need is Java version 21+.

You can check if Java is installed and its version by typing:

$ java -version

which should print something like:

openjdk version "21" 2023-09-19 LTS
OpenJDK Runtime Environment Temurin-21+35 (build 21+35-LTS)
OpenJDK 64-Bit Server VM Temurin-21+35 (build 21+35-LTS, mixed mode, sharing)

If Java is not installed or your version is too old, a newer version can be downloaded from Adoptium.

Once you have Java 21+ installed there are two ways to proceed:

  • You can use the Flix VSCode extension (highly recommended) or
  • You can run the Flix compiler from the command line.

Using Flix from Visual Studio Code (VSCode)

Flix comes with a fully-featured VSCode plugin. Follow these steps to get started:

  1. Create a new empty folder (e.g. my-flix-project).
  2. Open VSCode and choose File -> Open Folder.
  3. Create a new file called Main.flix in the folder.
  4. VSCode will ask you want to search the marketplace for extensions. Say "Yes".
  5. The Flix extension will be downloaded and installed. Once done, it will ask if you want to download the Flix compiler. Say "Yes" again.
  6. When you see "Starting Flix" followed by "Flix Ready!" everything should be ready.

A screenshot of the Flix Visual Studio Code extension in action:

Visual Studio Code1

Using Flix from the Command Line

Flix can also be used from the command line. Follow these steps:

  1. Create a new empty folder (e.g. my-flix-project).
  2. Download the latest flix.jar from and put it into the folder.
  3. Enter the created directory (e.g. cd my-flix-project) and run java -jar flix.jar init to create an empty Flix project.
  4. Run java -jar flix.jar run to compile and run the project.


The most common reasons for Flix not working are (a) the java command not being on your PATH, (b) the JAVA_HOME environmental variable not being set or being set incorrectly, or (c) having the wrong version of Java installed. To debug these issues, ensure that:

  • The command java -version prints the right Java version.
  • The JAVA_HOME environmental variable is correctly set.
    • On Windows, you can print the variable by typing echo %JAVA_HOME%.
    • On Mac and Linux, you can print the variable by typing echo $JAVA_HOME.

If you are still stuck, you can ask for help on Gitter.