Skip to content

Online JavaScript Compiler

Run JavaScript and see console.log output, with async/await, prompt() input and clear error messages. A safe playground that stops endless loops.

Private · on device. Runs in your browser: your file is not uploaded. No sign-up.

main.js
Output

Press Run (or Ctrl+Enter) to see the output here.

How to use an online JavaScript compiler

  1. Write JavaScript in the editor, or pick an example.
  2. Press Run (or Ctrl+Enter).
  3. Everything you console.log shows in the output; errors show in red with the line.
  4. For a web page with buttons and styles, use the HTML, CSS & JS tab instead.

Learning to code? The free courses in the Learn section go from beginner to expert, with tasks checked in this same editor. Other languages: all languages, Python, TypeScript, SQL, HTML, CSS & JS.

Frequently asked questions

Is this Node.js?

It is the JavaScript engine of your browser, in a worker with no page. Modern JavaScript works, including async/await and top-level await. Node-only modules such as fs are not available.

Can my program read input?

Yes. prompt() reads the lines you type in the Input box, one per call.

Why can I not use document or window?

Your code runs away from any page, so there is no document. To work with a page, choose the HTML, CSS & JS tab.

Is my code uploaded?

No. It runs in your browser and is kept only on this device.