Try Effekt Online

You can immediately experiment with the Effekt language, without installing it.

Effekt is a research language, we recommend reading the paper describing important design decisions and the inner workings of Effekt.

import immutable/list
import immutable/option
import text/string

Online Editor

Below you can find an online editor, which is enabled by clicking “edit” on the right. Please be aware that the changes are not saved!

interface Greet { def sayHello(): Unit }

def helloWorld() = try {
  do sayHello()
} with Greet {
  def sayHello() = { println("Hello!"); resume(()) }


The following read-eval-print-loop gives you access to run the above contents: