๐Ÿ‘️ HTML Previewer

Write or paste HTML, CSS & JavaScript — see live preview instantly

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๐Ÿ‘️ Live Preview
Console
๐Ÿ‘️ Full Screen Preview
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Testing HTML code usually means saving a file, opening a browser, refreshing, and repeating. That loop kills your flow. This free online HTML previewer lets you write or paste HTML, CSS, and JavaScript in separate tabs and see the rendered result instantly — no file saving, no downloads, no setup. Runs 100% in your browser, so your code stays on your device.

Switch between mobile, tablet, and desktop preview sizes. Open fullscreen mode. See console output. Upload existing .html files or download your combined code when finished. One tool, zero friction.

๐Ÿ“‘ Table of Contents

How to Preview HTML Code Online — Step by Step

  1. Write or paste your HTML. The HTML tab is active by default. Type your markup or paste existing code. Switch to the CSS and JS tabs to add styles and scripts separately.
  2. Click "Run Preview" (or enable Auto-run). With Auto-run checked, the preview updates as you type. Without it, click the red Run button to refresh the preview manually.
  3. Choose a preview device size. Tap the ๐Ÿ“ฑ ๐Ÿ“ฒ or ๐Ÿ–ฅ️ buttons to see how your page looks on mobile (375px), tablet (768px), or full-width desktop.
  4. Check the console. Enable "Console" to see console.log output and JavaScript errors directly below the preview — no browser DevTools needed.
  5. Download or share. Click Download to save your combined HTML, CSS, and JS as a single .html file ready for deployment.

Already have code that needs formatting? Run it through the HTML Formatter first, then preview it here.

Why Use This Online HTML Previewer

  • Instant rendering — see your HTML output in real-time without saving or refreshing files
  • Separate code tabs — HTML, CSS, and JavaScript each get their own editor, keeping your code organized
  • Responsive device preview — test mobile (375px), tablet (768px), and desktop layouts in one click
  • Built-in console — view console.log output and JS errors without opening browser DevTools
  • Fullscreen preview — expand the rendered page to fill your entire screen for accurate testing
  • File upload & download — load existing .html files, edit, and download the result as a complete file
  • 100% private — everything runs locally in your browser, no code sent to any server

Common Use Cases

Testing code snippets while learning HTML

Following a tutorial on MDN Web Docs? Paste each example into this previewer and see the result immediately. Experiment by changing values and watching what happens — that's faster than any textbook explanation.

Previewing email HTML templates

Email HTML behaves differently from web HTML. Paste your email template code here to check the visual layout before sending. Use the mobile preview to verify it looks correct on phone screens, where 60%+ of emails are read.

Quick prototyping for web design ideas

Sketch a layout idea with HTML and CSS without setting up a local project. The separate tabs keep your CSS clean, and the device-size buttons let you test responsive behavior instantly. When you're happy, download the complete file.

Debugging CSS issues

Isolate a CSS problem by pasting just the relevant HTML and CSS into the previewer. The stripped-down environment removes interference from other stylesheets. When you find the fix, apply it to your project. For formatting your CSS cleanly, use the CSS Formatter.

Reviewing code before minification

Before running your code through the HTML Minifier or JS Minifier, preview it here to confirm everything renders correctly. That way you know any post-minification issues are from the minification, not from your source code.

How Live HTML Preview Works

The previewer combines your HTML, CSS, and JavaScript into a single document, then renders it inside a sandboxed <iframe>. The iframe acts like a separate browser window — your code runs in its own isolated environment without affecting the parent page.

The sandbox attribute restricts what the previewed code can do: it can run scripts and show modals, but can't access your cookies, navigate the parent page, or interact with other tabs. This keeps your browsing session safe even if the previewed code has errors.

Device size previewing works by constraining the iframe's max-width. A 375px limit simulates an iPhone viewport. A 768px limit simulates an iPad. The full-width setting removes constraints. This doesn't replicate every device quirk, but it catches 90% of responsive layout issues — which is what responsive design is fundamentally about.

The console feature intercepts console.log, console.error, and console.warn calls from the iframe and displays them in the tool's own console panel. This avoids the need to open browser developer tools on mobile devices, where DevTools access is limited or nonexistent.

Tips & Best Practices

Use separate tabs for cleaner code

Put your CSS in the CSS tab and JavaScript in the JS tab instead of writing inline <style> and <script> tags inside the HTML. The previewer automatically wraps them into the correct document structure.

Turn off Auto-run for heavy scripts

If your JavaScript does intensive work (loops, API calls, DOM manipulation), disable Auto-run and use the manual Run button. This prevents the preview from re-executing on every keystroke.

Test mobile-first

Start with the ๐Ÿ“ฑ mobile preview. If your layout works on 375px, scaling up to tablet and desktop is usually straightforward. The reverse is rarely true.

Use the console for debugging

Instead of alert() for debugging (which blocks the preview), use console.log() and enable the Console panel. You'll see output and errors without interrupting your workflow.

Download to keep your work

The previewer doesn't save your code between sessions. If you've built something worth keeping, click Download to save a complete .html file. The file includes your HTML, CSS in a <style> tag, and JS in a <script> tag — ready to open in any browser.

Format before previewing

Messy code is hard to debug visually. Run your HTML through the HTML Formatter first. Clean indentation makes it easier to spot structural issues in the preview.

⚠️ Disclaimer: This tool renders HTML in a sandboxed iframe for preview purposes. Results may vary slightly across browsers. No guarantees are made regarding pixel-perfect rendering or complete browser compatibility. Always test final code in your target environment.

Frequently Asked Questions

Can I preview HTML code online without downloading any software?

Yes. This tool runs directly in your browser with no downloads or installations required. Paste your HTML code and click "Run" to see the preview instantly. Works on both desktop and mobile with equal performance.

Is there an HTML viewer that works on Android?

This tool works on any Android browser (Chrome, Firefox, Samsung Internet) without needing a separate app. Open the page, paste your code, and see the result. No need to download a dedicated HTML viewer APK.

How do I open an HTML file in the browser directly?

Click the "Upload .html" button in the tool and select an HTML file from your device. The tool reads the file and displays its content in the editor, with the preview rendering automatically. You can edit the code and download the modified version.

Is this HTML code previewer free to use?

Yes, completely free. No signup, no daily limits, no ads blocking your output. Everything runs locally in your browser — your code is never uploaded to any server.

Can I preview HTML with CSS and JavaScript together?

Absolutely. The tool has three separate tabs for HTML, CSS, and JavaScript. Write each in its own tab and the previewer combines them into one rendered page. You can also write everything in the HTML tab using inline <style> and <script> tags.

Can I use this tool as an online HTML editor?

Yes. The tool functions as a lightweight online HTML editor with live preview. Write your code, see the result in real-time, and download the final file. Ideal for learning, quick testing, and building prototypes.

Does the previewer support responsive testing?

Yes. Three device-size buttons simulate mobile (375px), tablet (768px), and desktop (full-width) viewports. Use them to check how your responsive CSS media queries behave across different screen sizes.

Previewing HTML shouldn't require local file setups or heavyweight IDEs. This online HTML previewer gives you a code editor, live rendering, responsive device testing, and console output — all in one browser tab. Bookmark it for quick tests, learning sessions, and prototyping. For production-ready code, clean it up with the HTML Formatter and optimize it with the HTML Minifier.