Developer toolsCodeRuns in your browserReviewed October 1, 2026

JavaScript Editor

Write and run JavaScript in your browser with syntax highlighting, a live console, async/await and error line numbers. Fast, private and easy to use in your browser.

Localprivate by defaultFastno sign-up path

Browser-local code runner

Your code runs in a background worker on this device and is never uploaded.

// Press Run (or Ctrl/Cmd + Enter)
const name = "AllConvertTools";
console.log("Hello from", name);
console.log({ sum: 2 + 3, list: [1, 2, 3].map((n) => n * 2) });

Console

Output appears here. Use console.log(...) in your code.

Loading code editor...

JavaScript Editor Online

A free online JavaScript editor and runner. Write code with syntax highlighting, auto-closing brackets and automatic indentation, run it in an isolated background worker and see console.log output, errors with line numbers, async/await and timers. Long-running code can be stopped, and nothing leaves your device.

How to use JavaScript Editor

Type or paste JavaScript, or load an example.
Press Run or Ctrl/Cmd + Enter.
Read console.log output and errors in the console, then copy or download your script.

Questions

Does this upload my data?

No. This converter runs in your browser for ordinary use, so the input is not sent to a backend by this tool.

Can I use the DOM or window?

This editor runs code in a Web Worker, so there is no document or window. Use the HTML, CSS and JS playground when you need to work with a page.

Does it support async and await?

Yes. Top-level await works, and timers and fetch run normally.

What if my code loops forever?

Press Stop, or wait: the run is stopped automatically after 10 seconds.

Related tools

Keep working without searching again.

Code