JavaScript & HTML Playground

Local only

Write HTML, CSS, and JavaScript with a sandboxed preview and captured console.

Ready to run
<main class="welcome-card">
  <span class="eyebrow">Nobuf Playground</span>
  <h1 id="greeting">Build something useful.</h1>
  <p>Edit HTML, CSS, and JavaScript, then see the result instantly.</p>
  <button id="hello-button" type="button">Say hello</button>
  <output id="message" aria-live="polite"></output>
</main>
HTMLLn 1, Col 1
Preview
Console0

Run the playground to see console output.

0 console messages

Code runs inside an isolated browser iframe. Nobuf does not upload or inspect it.1,622 source characters

How to use it

  1. 01

    Write your source

    Use syntax-highlighted HTML, CSS, and JavaScript editors with preserved cursor and undo history.

  2. 02

    Run in the sandbox

    Preview DOM output and inspect logs, warnings, runtime errors, and rejected promises without executing code in the parent page.

  3. 03

    Save or export

    Keep a versioned local draft, import a project, or download a clean standalone HTML file.

Frequently asked questions

Is my code uploaded to Nobuf?

No. Editing, document construction, preview execution, and console capture happen in your browser. A versioned draft is stored only in this browser.

How is untrusted JavaScript isolated?

Code runs in a sandboxed iframe without same-origin or top-navigation permission. Messages are accepted only from the current iframe with matching random channel and run identifiers.

Can it run Node.js or npm packages?

It runs browser JavaScript, not Node.js. ES Modules and import maps work, but Node built-ins, require, process, and bare npm imports are unavailable unless you map a browser-compatible URL yourself.

Can Stop always interrupt an infinite loop?

Stop replaces the sandbox and invalidates old messages, but browser process scheduling means no same-page iframe can promise to recover from every synchronous loop. Avoid running code you do not trust.

Keep working with other private browser utilities.

All tools

All processing happens locally in your browser.

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Nobuf

Fast, private utilities powered by your browser.