JS Formatter Console

Ready

Everything you need to write JavaScript online

A full-featured code playground that runs right in your browser — no install needed.

Run JavaScript Instantly

Type or paste code and execute it with a click. Results appear immediately in the Console panel, including logs, errors, and return values.

Render HTML & CSS Live

Switch to HTML or CSS mode and preview your full web page rendered in the Output tab. Great for quickly prototyping layouts and styles.

Monaco Editor — VS Code Quality

Write code with the same editor that powers VS Code. Syntax highlighting, IntelliSense, bracket matching, and more — all in the browser.

Loop Protection Built-in

Infinite loop detection automatically stops runaway code before it freezes your browser. Safe to experiment freely without any risk.

Auto-saves Your Work

Your code is preserved in your browser between sessions. Close the tab and come back later — everything is still there waiting for you.

Dark & Light Theme

Switch between themes to suit your environment. Dark mode for night sessions, light mode for bright screens — one click to change.

Who is it for?

Students & Learners

Learning JavaScript? Practice concepts, test examples from tutorials, and see how code behaves — all without any setup or installation.

Developers Debugging

Quickly isolate a bug without spinning up a full project. Paste the problematic snippet, run it, and find the issue in seconds.

Rapid Prototyping

Turn an idea into working code instantly. Test an API response, validate a regex, or sketch a UI concept without any boilerplate.

Have questions?

How do I run JavaScript online?

Type or paste your JavaScript into the editor and press Ctrl+Enter (or Cmd+Enter on Mac). Your code executes instantly and the output appears in the Console panel on the right.

Does it support HTML and CSS?

Yes. Click the HTML or CSS tab at the top to switch modes. Then open the Output tab to see your rendered page. All three languages work together and are combined and rendered live.

Is my code saved between sessions?

Yes. Your code is automatically saved to your browser's local storage after every change. Close the tab, come back later — your last code will still be there.

What is the difference between the Console and Output tabs?

Console shows the results of JavaScript execution — console.log output, errors, and return values. Output renders your HTML and CSS as a live web page inside a sandboxed frame.

Is it free to use?

Yes, completely free with no sign-up or account required. Just open the page and start coding.