The JavaScript playground
for your desktop

const limit = 15;
let count = 1;
Array(limit).fill(0).reduce((acc, _, index) => {
  const spaces = ' '.repeat(
    Math.abs(limit - count) / 2
Other platforms

Explore and experiment with JavaScript and TypeScript, visualise your ideas and get instant feedback as you type.


Latest version: 2.6.0

macOS (.app)Universal
Windows (.exe)64 bit
Linux (.deb)64 bitARMARM 64
Linux (.tar.gz)64 bitARMARM 64


Exploring JavaScript has never been easier. Live feedback as you type, with per-line results makes it super clear what your code is doing.

Web Audio

With RunJS you have access to Node and Browser APIs, including full DOM access. This gives you a level of versatility that's not possible in a standard REPL or Chrome console.

Babel and TypeScript support enables you to write modern, up-to-date syntax.


NPM integration makes trying out new libraries quick and easy.Premium



Since the first release of RunJS in late 2018, many people from around the world, with all kinds of backgrounds have said very kind words about it.

Awesome JS playground here. Its similar to Swift playgrounds - every line of JS code will be evaluated separately, with output printed on the right. Great tool for exploring JS!
Stephen Grider

Stephen Grider

RunJS - a desktop app that serves as a JavaScript scratchpad. This is one of my favorite tools for debugging and testing things quickly.
Joe Previte

Joe Previte

If you want to know what a piece of JS code will do, there's no substitute for just RUNning it and seeing the result! RunJS has become an essential tool in my daily JS development, writing, and teaching work, unseating a bunch of other tools like consoles, CLIs, and in-browser code editors.
Kyle Simpson

Kyle Simpson

This. is. awesome: RunJS, a JavaScript playground for Mac. Supports TypeScript, Babel transpilation, Node and browser APIs altogether, import Node modules from a folder, and more.
Flavio Copes

Flavio Copes

Was looking for a simple Javascript REPL Mac app and ran across RunJS.. this is perfect. simple little sandbox to tinker with JS before writing it for real in my main environment.
Paul Stamatiou

Paul Stamatiou

I teach code school and mentor junior engineers at work. When there’s a question about the language, it is so easy to just throw RunJS up on the screen and run little experiments in a safe and clear environment until everybody’s got the behavioural info they need to make a choice.
Al Zimmerman

Al Zimmerman

So grateful to have discovered RunJS. It's so much easier to practice JavaScript when you can see the solution in real time!
Cassandra Rossall

Cassandra Rossall

RunJS icon

Go on, give it a try.

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