Free HTML Viewer - Preview HTML Online
Paste HTML and instantly see a live preview with formatted source code.
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Output
What Is an HTML Viewer?
Building an email template and need to see how it actually looks? Debugging a component and want to check the output without spinning up a dev server? An HTML viewer lets you paste markup and instantly see a live preview — no setup needed. The preview renders in a sandboxed iframe using the srcdoc attribute, so your CSS and inline styles render exactly as they would in a real browser. It's also handy for reviewing auto-generated HTML from tools like WordPress or CMS exports, and for sharing visual previews with teammates who aren't comfortable reading raw markup.
This tool runs entirely in your browser. The preview is rendered in a sandboxed iframe using the srcdoc attribute — a feature defined in the WHATWG HTML Living Standard. For a full reference on HTML elements and attributes, MDN Web Docs is the go-to resource. The Source tab shows the formatted HTML source code.
How to Use This Tool
Paste or Upload HTML
Paste your HTML into the left editor, or click Upload to load a file. Click Sample to try an example.
Preview or View Source
The right panel shows a live Preview of your HTML. Switch to the Source tab to see the formatted HTML source code.
Copy or Download
Use Copy or Download to save the formatted source. To validate your HTML for errors, try the HTML Validator tool.
HTML Viewer Example
Paste any HTML snippet and see it rendered instantly. Here is a simple example:
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When an HTML Viewer Is Useful
An HTML viewer is useful when you want to quickly test HTML snippets without a browser DevTools setup, check email templates, review auto-generated HTML, or share a visual preview of HTML with colleagues.
For validating HTML structure and catching errors, use the HTML Validator tool.
Frequently Asked Questions
Is the preview sandboxed?
Yes. The preview runs inside a sandboxed iframe with the sandbox="allow-scripts" attribute. This prevents the preview from accessing cookies, localStorage, or navigating the parent page.
Is my HTML sent to a server?
No. The preview is rendered entirely in your browser using the srcdoc iframe attribute. No data is sent anywhere.
Can I preview full HTML pages with CSS?
Yes. Paste a complete HTML page including <style> tags and external CSS links. The iframe will render it as a browser would.
Related Tools
The HTML Living Standard documents the srcdoc attribute used for the preview. See MDN iframe documentation for sandbox details.