How to Use the HTML Live Preview
Get started in seconds — no installation, no sign-up, no credit card required.
Write Your Code
Type or paste any HTML into the left editor panel. Include <style> for CSS and <script> for JavaScript. The editor supports Tab key indentation and preserves your formatting.
Watch It Render
As you type, the preview pane updates automatically with a 300ms debounce. See your HTML, CSS, and JavaScript come to life instantly in a secure sandboxed iframe.
Test Responsive Layouts
Use the Desktop, Tablet (768px), and Mobile (375px) buttons to simulate different screen sizes. Perfect for testing CSS media queries and breakpoints.
Copy or Download
When you're happy with your code, click "Copy HTML" to grab it to your clipboard, or hit "Download" to save it as a .html file for local use.
Toggle Word Wrap
Writing long lines? Enable word wrap to keep everything visible without horizontal scrolling. Great for working with minified code or pasted snippets.
Clear and Start Fresh
Hit the "Clear" button to reset the editor to a blank slate. Perfect for starting a new experiment without closing the tab and losing your place.
Why Developers Love This Tool
Built by developers, for developers. Every feature is designed to make your workflow faster.
Instant Real-Time Preview
See your changes immediately as you type. The 300ms debounce ensures smooth performance even with large documents, and the live indicator lets you know when the preview is syncing.
Sandboxed & Secure
Your code runs in a sandboxed iframe with allow-scripts allow-same-origin permissions. Scripts cannot access cookies, localStorage, or the parent page — perfect for testing untrusted code.
Responsive Device Simulation
Toggle between Desktop, Tablet (768px), and Mobile (375px) viewports to test CSS breakpoints. The preview constrains to exact pixel widths so your media queries fire correctly.
Export Options
Copy your HTML to the clipboard with one click, or download it as a .html file. Both methods preserve your exact formatting, including indentation and line breaks.
Developer-Friendly Editor
Tab key works for indentation (inserts 2 spaces). Monospace font. Optional word wrap. Character and line count in the status bar. Everything a code editor should have.
100% Browser-Based
No installation, no account, no server uploads. Everything runs entirely in your browser using native APIs. Your code never leaves your machine unless you choose to share it.
What You Can Build
From quick tests to full prototypes — see what's possible.
Test CSS Layouts
Try out flexbox, grid, positioning, or any CSS property. See the result instantly without touching your production codebase.
UI Component Prototyping
Design buttons, forms, cards, and navigation before committing to your framework. Test colors, spacing, and interactions.
JavaScript Debugging
Test DOM manipulation, event listeners, fetch calls, or any JavaScript code. Open browser DevTools to see console logs and inspect the preview.
Responsive Design Testing
Write mobile-first CSS and test it across viewports using the device buttons. See exactly how your breakpoints behave.
Frequently Asked Questions
Everything you need to know about using the HTML Live Preview tool.
Does this support CSS in <style> tags and JavaScript in <script> tags?
Yes! You can include any valid HTML, CSS, and JavaScript. The preview iframe renders everything just like a real browser tab. External resources (CDN links, Google Fonts, etc.) also load normally, so you can test with libraries like Bootstrap or jQuery.
Is my code saved anywhere? Can others see it?
No. Everything runs 100% locally in your browser. Your code is never sent to our servers, never stored, and never visible to anyone else. Once you close the tab, the code is gone unless you downloaded it first. This tool respects your privacy completely.
What do the Tablet and Mobile buttons actually do?
They constrain the preview iframe to fixed widths: 768px for Tablet and 375px for Mobile. This simulates smaller screens so your CSS media queries fire correctly. It's the same concept as using browser DevTools responsive mode, but built directly into the tool.
Is there a character or file size limit?
There's no enforced limit. Very large documents (hundreds of KB) may render slightly slower due to browser memory constraints, but typical HTML pages (even full frameworks) work perfectly fine. If you're pasting 10,000+ lines, consider enabling word wrap for easier reading.
Can I test JavaScript that manipulates the DOM or uses APIs?
Yes. The iframe sandbox allows allow-scripts and allow-same-origin, so document.querySelector(), event listeners, timers, and most Web APIs work as expected. Network requests (fetch, XHR) work too, though CORS restrictions still apply from the iframe context.
How is this different from CodePen, JSFiddle, or CodeSandbox?
It's intentionally simpler. CodePen and JSFiddle separate HTML, CSS, and JS into different panes — this tool gives you one unified HTML editor where you write everything together, just like a real HTML file. Great for testing full snippets without splitting your code. No account, no saving, no sharing features — just pure instant preview.
Can I use this offline?
Once the page loads, the core editor and preview functionality work offline since everything runs in the browser. However, you'll need an internet connection to access the page initially, and any external resources (CDN libraries, web fonts) won't load offline.
What browsers are supported?
All modern browsers: Chrome, Firefox, Safari, Edge, Opera. The tool uses standard Web APIs (iframe.srcdoc, Blob URLs, Clipboard API) that are universally supported. Internet Explorer is not supported.