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Hazuu Tools

Realtime HTML Editor

Write HTML, CSS, and JavaScript with instant live preview. A CodePen-like editor that runs entirely in your browser.

Live Preview
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code3 panels opendata_objectHTML: 0 charspaletteCSS: 0 charsjavascriptJS: 0 chars
info

About Realtime HTML Editor

The Realtime HTML Editor is a three-panel browser-based playground that lets you write HTML structure, CSS styling, and JavaScript behaviour in separate colour-coded panels while a live preview iframe updates as you type. Unlike a static code editor, there is no save-and-refresh step — each keystroke rerenders the output immediately, giving you a tight feedback loop that is hard to replicate in a traditional text editor.

The tool is built around a sandboxed iframe that uses the srcdoc attribute to combine your three code panels into a complete HTML document on every change. This approach means external CSS frameworks or JavaScript libraries loaded via CDN links in the HTML panel work just as they would in a real browser tab, while the sandbox attribute prevents the preview from accessing cookies, local storage, or the parent page. It is the right tool when you need to prototype an interactive component, debug a CSS layout issue without spinning up a local dev server, or share a reproducible snippet with a colleague.

Everything runs entirely inside your browser. Your code is never transmitted to a server, stored in a database, or analysed in any way. There are no accounts, no rate limits, and no cost. The "Copy All" button packages your HTML, CSS, and JavaScript into a single self-contained HTML file you can save or send to anyone without losing the structure.

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Key Features

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Three dedicated code panels

HTML (blue), CSS (pink), and JavaScript (yellow) panels are kept separate so you can focus on structure, style, or behaviour independently without scrolling through one big file.

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Instant iframe preview

The live preview pane rerenders on every keystroke using a sandboxed srcdoc iframe. No manual refresh, no build step — you see the result as fast as you can type.

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Collapsible panels

Click any panel header to collapse it. Working on CSS-only tweaks? Hide the JavaScript panel and give your screen space to the panels you actually need.

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Vertical and horizontal layouts

Switch between vertical (code above, preview below) and horizontal (code left, preview right) with one click to match your monitor orientation and personal preference.

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Copy All as a complete HTML file

The "Copy All" button exports your three panels as a single valid HTML document with inline style and script tags — paste it into any file and it works immediately.

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Load a working sample

Click "Sample" to load a real interactive card component with a gradient header, hover animation, and a click counter, giving you a concrete starting point to modify rather than a blank page.

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How to Use

01

Write Your Code

Enter HTML in the blue panel, CSS in the pink panel, and JavaScript in the yellow panel. Each panel can be collapsed if you do not need it.

02

See Live Output

The preview pane updates in real time as you type. Switch between vertical and horizontal layouts to suit your screen.

03

Copy or Reset

Click "Copy All" to grab the combined HTML document, or use "Clear" to start fresh. Load the sample demo to see a working example.

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Example

Write HTML, CSS, and JavaScript in the three panels and the preview iframe updates immediately. The output below shows what the browser renders — no refresh required.

HTML panel
<div class="box">
  <h2>Hello, World!</h2>
  <button id="btn">Click me</button>
  <p id="msg"></p>
</div>
Live preview renders
A white rounded box appears centered on a blue gradient background.
"Hello, World!" is displayed as a heading.
A styled button reads "Click me".
Clicking it shows "You clicked 1 time!" in the paragraph below — updated live on every click, with no page reload.
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Common Use Cases

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    Front-end prototyping without a local server

    Sketch out a UI component — a modal, a card, a navigation bar — and see exactly how it looks and behaves in a browser without creating a project, installing dependencies, or running a dev server. Save the result with "Copy All" when you are satisfied.

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    Learning HTML, CSS, and JavaScript interactively

    Students and self-taught developers benefit from immediate visual feedback. Change a CSS property and watch the layout shift in real time, or add an event listener and click the element to confirm the JavaScript fires correctly. This tight loop accelerates understanding.

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    Debugging layout or animation issues in isolation

    Copy a problematic component out of your main codebase, paste it into the three panels, and strip it down until you find the CSS rule or JS interaction that is causing the problem. Isolation is faster than debugging inside a large project.

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    Writing reproducible bug reports

    When filing a bug report or asking for help, paste your minimal HTML, CSS, and JavaScript into this editor and share the "Copy All" output. The recipient gets a standalone file that reproduces the issue exactly, with no environment variables or build tools required.

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    Experimenting with CDN libraries before adding them to a project

    Add a script tag pointing to a CDN build of a library in the HTML panel and test its API immediately. This is faster than installing a package locally when you just want to evaluate whether a library fits your needs.

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Frequently Asked Questions

What is a Realtime HTML Editor? expand_more
A Realtime HTML Editor is an online tool that combines separate HTML, CSS, and JavaScript code panels with a live preview iframe. As you type in any panel, the preview updates instantly so you can see exactly how your code renders in a browser without manually refreshing.
Is my code sent to a server? expand_more
No. All code stays in your browser. The preview is rendered using a sandboxed iframe with the srcdoc attribute, so nothing is uploaded or stored on any server. Your work remains completely private.
Can I use external libraries or frameworks? expand_more
Yes. You can include external CSS or JavaScript libraries by adding link or script tags with CDN URLs directly in the HTML panel. The iframe will load and execute them just like a normal web page, so Bootstrap, Alpine.js, Chart.js, and similar libraries all work.
Does the JavaScript panel support modern syntax? expand_more
The JavaScript you write runs natively in your browser engine, so any syntax your browser supports — ES6+, async/await, arrow functions, optional chaining — will work in the editor. No transpilation step is involved.
How is this different from the HTML Viewer tool? expand_more
The HTML Viewer renders a single HTML document you paste in and is designed for reading or checking the output of existing markup. This Realtime HTML Editor gives you three separate editable panels for HTML, CSS, and JavaScript that update a live preview as you type — it is a writing and prototyping environment, not a read-only viewer.
How is this different from the HTML Formatter tool? expand_more
The HTML Formatter takes messy or minified HTML and reformats the indentation so it is easier to read. This editor does not format code — its purpose is to let you write and run HTML, CSS, and JavaScript together and see the visual result immediately. They solve different problems: one cleans up code, the other lets you build and test it.
Can I save my work? expand_more
Click "Copy All" to copy a complete standalone HTML file to your clipboard. Paste it into any text editor and save it as an .html file. The file includes your HTML structure, an inline style block, and an inline script block, so it runs in any browser without additional setup.
Does the sandbox block all JavaScript? expand_more
The iframe uses the sandbox="allow-scripts" attribute, which permits JavaScript execution while blocking access to the parent page, cookies, local storage, and form submission. Standard DOM manipulation, event listeners, fetch calls, and timers all work normally within the preview.