Real-Time HTML Editor – Live HTML Preview Online

HTML Editor

Live Preview

What Is a Real-Time HTML Editor?

A real-time HTML editor lets you write HTML in a code panel and see the rendered result side-by-side as you type. No saving, no refreshing, no terminal — just immediate visual feedback. It's the fastest way to prototype a layout, test a snippet, or see exactly what your markup produces.

Under the hood, every keystroke updates an iframe via its srcdoc attribute, so the preview is fully sandboxed from the rest of the page. That means scripts inside your HTML can run safely without touching the outer app.

How to Use This Editor

Write or paste your HTML

Type directly in the left panel, paste a snippet from your project, or hit Sample to load a working example. The editor uses ACE with full HTML syntax highlighting.

Watch the preview update

The right panel renders your HTML live inside a sandboxed iframe. Changes appear within 300 ms of your last keystroke — no button to click, no page to reload.

Copy or download your result

When you're happy with the result, hit Copy HTML to grab the source, or Download to save it as an .html file.

Example: A Simple HTML Page

Here's a realistic snippet you can paste straight into the editor. It shows a heading, a paragraph with a styled button, and a bit of inline CSS — enough to see the live preview in action.

Input

HTML

Frequently Asked Questions

Is my HTML sent to any server?

No. Everything runs entirely in your browser. Your HTML is never uploaded anywhere — it's rendered locally using the browser's built-in iframe engine.

Can I run JavaScript inside the preview?

Yes. The iframe is sandboxed with allow-scripts allow-same-origin, so inline JavaScript executes normally. Just be careful with scripts that try to access parent-frame resources — the sandbox blocks those by design.

What file types can I upload?

You can upload .html, .htm, and .txt files. The contents are loaded directly into the editor, so you can immediately start editing and see the preview update.

Does this tool support CSS and JavaScript in the same file?

Absolutely. The preview renders a full HTML document, so you can include <style> blocks for CSS and <script> tags for JavaScript. For external resources, the iframe needs a network connection since it runs in the browser like any web page.

Why use an iframe instead of innerHTML?

An iframe with srcdoc gives you a completely isolated document context. CSS and JS in the preview can't accidentally affect the editor page. It also supports a full HTML5 document structure including <head> and <body>.

Can I use this as a quick HTML prototyping tool?

That's exactly what it's built for. Drop in a snippet from Bootstrap, Tailwind, or your own project and see how it looks instantly. No local dev server needed.

Real-Time HTML Editor – Write & Preview HTML Instantly