Code Playground

Write HTML, CSS, and JavaScript with live preview. Like a mini CodePen — entirely in your browser.

Related Tools

How to Use

1. Write Your Code — Switch between the HTML, CSS, and JS tabs to write your code. Each tab has a dedicated editor with tab-key indentation and monospace font. The preview updates automatically as you type (500ms debounce).
2. See Live Preview — The preview panel shows your rendered output in a sandboxed iframe. HTML structure, CSS styling, and JavaScript interactions all work together in real-time. Open the Console to see console.log output and any errors.
3. Export Your Work — Click Download .html to save your project as a single HTML file with embedded CSS and JS. Click Copy Code to copy all three sections to your clipboard. The exported file works standalone in any browser.

About the Code Playground

WritePadPro's Code Playground is a lightweight, browser-based code editor with three separate panels for HTML, CSS, and JavaScript, plus a live preview that updates as you type. It provides the core experience of tools like CodePen, JSFiddle, and JS Bin — but runs entirely in your browser with zero server dependency, zero account requirements, and complete privacy.

Who Needs a Code Playground?

• Bloggers — test HTML/CSS snippets before adding them to your CMS. Preview custom widgets, embedded content, and styled sections.
• Email developers — build and preview HTML email templates. Test inline styles and table layouts that email clients require.
• Students — learn HTML, CSS, and JavaScript interactively. Write code and see results immediately without setting up a development environment.
• Developers — quickly prototype UI components, test CSS animations, debug JavaScript logic, or create shareable code examples.
• Designers — experiment with CSS layouts, gradients, animations, and responsive designs in a contained environment.

Architecture

The preview uses an iframe with srcdoc attribute. Your HTML, CSS, and JS are combined into a complete HTML document and injected into the iframe as a data URL — no server request is made. The iframe is sandboxed from the parent page, meaning your code cannot access WritePadPro's DOM, cookies, or JavaScript context. This provides security isolation while allowing full browser API access within the preview.

Console Integration

The playground includes a built-in console panel that captures output from your JavaScript. The preview iframe's console.log, console.warn, and console.error are intercepted and forwarded to the parent page via postMessage. Runtime errors are caught via window.onerror and displayed with line numbers. This gives you debugging capability without opening browser DevTools.

Single-File Export

Click Download to save your project as a single .html file. The exported file is completely self-contained — CSS is embedded in a <style> tag and JavaScript in a <script> tag. No external dependencies. The file opens in any browser and works identically to the preview. This is perfect for sharing prototypes, submitting assignments, or deploying simple pages.

Performance

The auto-run feature uses a 500ms debounce — the preview only rebuilds when you stop typing for half a second. This prevents performance issues from rapid-fire iframe rebuilds during fast typing. For JavaScript-heavy projects, you can disable auto-run and use the manual Run button for full control over execution timing.

Privacy

Every line of code you write stays in your browser. The iframe preview uses srcdoc (inline HTML), not a server URL. No code is transmitted, compiled remotely, or stored anywhere outside your browser tab. When you close the tab, the code is gone unless you download it first. This makes the playground safe for prototyping with proprietary designs, private API logic, or confidential content.