Online JavaScript Playground — Run JS in Your Browser

Test JavaScript ideas in seconds: write code in the JS tab and watch it execute against real HTML in a sandboxed preview about one second later. A captured console shows logs, warnings and errors, so you can debug quickly — then download the working snippet or share it with a link. Nothing to install, no account needed.

Open the free editor

Built for fast JavaScript experiments

Real DOM, real events

Your script runs against live HTML with working event listeners — click buttons, submit forms and test interactions exactly as users would, not in a simulated console-only sandbox.

Console output captured

console.log, console.warn, console.error, uncaught errors and unhandled promise rejections all appear in a built-in console panel with timestamps and level badges.

Snippet completions that keep you typing

Curated JavaScript snippets — querySelector, addEventListener, fetch, loops and more — appear as you type and are inserted with Tab, including inline ghost-text suggestions for names you have already used.

Sandboxed execution

Each run executes inside a sandboxed iframe, isolated from the editor itself — so a crashing experiment never takes the playground down, and errors stay contained where you can read them.

Auto-run with manual override

Auto-run re-executes your code about a second after you stop typing. Turn it off when iterating on long-running logic and use Run (or Ctrl+Enter) whenever you are ready.

Export or share the whole thing

Download a single HTML file with your script inlined, a ZIP with script.js separated, or save the project and send a permalink that reopens your exact code for anyone.

How to run JavaScript online in 4 steps

  1. 1

    Open the playground — the JS tab contains a tiny working demo (a live counter) so you can see execution and console output immediately.

  2. 2

    Edit or replace the code. Auto-run executes it against the preview page about a second after you stop typing.

  3. 3

    Open the console panel to inspect logs and errors, and use the HTML tab to add elements for your script to interact with.

  4. 4

    When it works, download the result as HTML or ZIP — or press Save to get a share link you can paste anywhere.

Questions this tool answers

Frequently asked questions

Can I run JavaScript online without installing Node?

Yes. This playground executes JavaScript in your browser — no Node, no terminal and no installation. It is ideal for DOM experiments, event handling and quick logic checks, and works from any device including phones and tablets.

Where do console.log and errors appear?

A console panel under the preview captures everything your script logs, plus uncaught errors and promise rejections, each with a timestamp and severity badge — like DevTools, but built into the workspace.

Is it safe to run code in the preview?

Your code executes in a sandboxed iframe that is isolated from the editor page itself. The playground stays responsive even if your script throws, and nothing is executed on a server.

Does auto-run re-execute my JavaScript automatically?

Yes — about one second after you stop typing, a fresh run starts so the preview always matches your code. You can set the delay to 0.5s or 2s, or switch to manual mode and press Run yourself.

Can my script use external libraries from a CDN?

Yes. Add a <script src> tag pointing to any CDN in the HTML tab and the library is loaded into the preview, so you can experiment with tools like chart libraries or animation engines.

How do I save or share my JavaScript snippet?

Press Save in the toolbar to store the project and receive a permanent link, or use Download to export a standalone HTML file or a ZIP with index.html, style.css and script.js.