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HTML Viewer & Live Editor

Write HTML, CSS and JavaScript in separate tabs — live preview, built-in console, resizable panes

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HTML Viewer — Preview HTML, CSS and JavaScript Instantly

The HTML Viewer gives you a full live code editor and sandboxed preview side by side. Write or paste any HTML — with embedded <style> and <script> blocks — and see it render in real time without leaving the browser. The preview runs in an isolated iframe so JavaScript executes safely without affecting the rest of the page.

Use the five built-in starter templates (blank page, card UI, login form, gradient hero, CSS animations) to jump-start your code. Switch between desktop and mobile viewport widths, toggle a dark preview background, and copy or download the finished HTML with one click. Everything runs 100% client-side — no server, no signup.

How it works

Live HTML Preview in 10 Seconds

01

Choose a template

Pick from Blank, Card UI, Login Form, Gradient Hero, or CSS Animation — or paste your own HTML.

02

Edit the code

Write HTML, CSS, and JavaScript in the code panel. Auto mode updates the preview as you type.

03

Preview instantly

See the rendered output in the live preview panel. Switch between desktop and mobile viewports.

04

Copy or download

Copy the HTML to clipboard or download as index.html for immediate use in your project.

Use cases

When to Use an Online HTML Viewer

🧪

Prototype UI components

Quickly test CSS layouts, animations, and component ideas without setting up a local project.

📧

Preview email HTML

Paste HTML email templates and check how they render before sending to a client or test inbox.

🎓

Learn HTML and CSS

Students and beginners can experiment with HTML tags and CSS rules and see results instantly.

🔍

Debug rendered markup

Paste server-generated HTML to check structure, class names, and styles in isolation.

🎨

Test CSS animations

Build and fine-tune CSS keyframe animations with a live preview that updates as you type.

📋

Share HTML snippets

Write a self-contained HTML snippet for documentation, a blog post, or a code review.

FAQ

Frequently Asked Questions

1Can I use external CSS libraries like Tailwind or Bootstrap?
Yes — add a <link> tag pointing to a CDN URL inside your <head>. For example, add the Tailwind CDN script tag and Tailwind utility classes will work in the preview. The sandbox allows network requests for loading CDN resources.
2What is the sandbox attribute used in the preview iframe?
The preview iframe uses sandbox="allow-scripts allow-forms allow-modals". This means JavaScript runs, forms can be submitted, and alert/confirm dialogs work — but the code cannot access parent page cookies, localStorage, or navigate the outer page.
3Is there a file size limit?
No hard limit — the editor is a standard textarea. Very large HTML documents (100KB+) may slow the preview slightly since the browser needs to parse and render them on each update. Use Manual mode for large documents to control when re-rendering happens.
4Can I use multiple files (CSS file + JS file)?
This is a single-file sandbox. Put all CSS in a <style> block and all JavaScript in a <script> block inside the same HTML document. For multi-file projects, use a local code editor like VS Code.
5How do I preview HTML online?
Paste your HTML into the editor and the preview renders instantly in a sandboxed pane. No signup required. The preview supports inline CSS, JavaScript, and CDN libraries.
6Is the HTML preview safe?
Yes. The preview runs in a sandboxed iframe that isolates code from the rest of the page. JavaScript executes without accessing parent page cookies or localStorage.
7How do I preview HTML emails?
Paste your HTML email markup and the preview renders it as a browser would. Switch to mobile viewport to verify responsive email designs before sending.
8How do I test HTML responsiveness?
Use the viewport toggle in the toolbar to switch between desktop and mobile widths. Check media queries, flexbox layouts, and responsive breakpoints without a separate device.
9How do I use an HTML sandbox?
Paste any HTML including JavaScript and CSS. The iframe sandbox allows scripts and forms while blocking parent page access. It is safe to test code from unknown sources.
10How do I preview Bootstrap HTML snippets?
Add the Bootstrap CDN link tag in your HTML head. The sandbox allows CDN resources so Bootstrap styles render immediately without any local setup.
11How do I debug HTML rendering issues?
Paste the problematic HTML snippet in isolation to see how it renders without other page styles interfering. Remove sections to identify which element causes the issue.
12How do I preview HTML without a project?
The HTML Viewer is a zero-setup sandbox — no local server or npm install needed. Paste any HTML fragment and see it rendered immediately. Use starter templates for common layouts.

Last updated: May 2026

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