Is it safe to preview untrusted HTML?

Yes. The preview renders inside a sandboxed iframe with scripts disabled, so embedded JavaScript cannot run or access your page, cookies, or storage.

Does JavaScript in the HTML run?

No. For your safety the sandbox blocks all scripts, so the preview shows only the HTML structure and CSS styling, not script-driven behaviour.

Is my HTML sent to a server?

No. The markup is rendered locally with the iframe srcdoc attribute, so your HTML never leaves your browser.

Can I see the raw source too?

Yes. Toggle to the source view to read the escaped, formatted markup alongside the rendered preview.

Can I preview a full HTML document?

Yes. Paste a complete document including , , and and the sandbox renders it just as a browser would, minus any scripts.

Will external images and stylesheets load?

Images and stylesheets referenced by absolute URLs may load, but the sandbox blocks scripts; for full fidelity inline your CSS in the markup.

Does it modify or format my HTML?

No. The rendered view uses your markup as-is, and the source view only escapes characters for display without changing the underlying code.

HTML Viewer & Previewer

Paste any HTML and see it rendered live in a sandboxed preview, or flip to the source view to read the raw markup — no scripts run, nothing is uploaded, and it all happens in your browser.

Updated June 2026

Files never leave your browser

HTML Code

Rendered in a sandboxed iframe with scripts disabled — your HTML is never uploaded.

How to use HTML Viewer & Previewer

The HTML Viewer renders your markup live in a safe, sandboxed preview while keeping everything on your device. Paste a snippet or a full page source and instantly see how it looks, then flip to the source view to read the formatted, escaped markup. Scripts are disabled in the sandbox so even untrusted HTML is safe to inspect, and because rendering uses the iframe srcdoc attribute locally, your code is never uploaded.

Paste your HTML markup into the input box — a fragment or full page both work.
Click "Preview" to render it inside the sandboxed iframe.
Toggle between "Rendered" and "Source" to compare output and markup.
Edit and preview again as needed — nothing is uploaded.

Your data never leaves your device — 100% private processing.

How the safe preview works

Your markup is injected into an iframe using the srcdoc attribute with an empty sandbox value, which disables scripts, form submission, popups, and same-origin access. That means embedded JavaScript cannot run, read your cookies, or reach the parent page, so you can safely inspect HTML from any source. CSS still applies, so the rendered view faithfully reflects layout and styling while remaining isolated from the rest of the tool.

Rendered view versus source view

The rendered view shows the visual result a browser would paint. The source view escapes the same markup — converting <, >, &, and quotes into entities — so you can read the exact tags and attributes without them being interpreted. Switching between the two helps you connect a piece of markup to its on-screen effect, which is useful for debugging layout issues or learning how elements nest.

Worked examples

Render a heading and paragraph

Inputs: <h1>Hi</h1><p>Body text</p>

Result: Shows a large "Hi" heading above body text

Preview inline-styled markup

Inputs: <p style="color:teal">Teal</p>

Result: Renders the word "Teal" in teal colour

Inspect the source

Inputs: Toggle to Source view

Result: Markup shown as escaped, readable text

Glossary

Sandboxed iframe: An embedded frame with restricted capabilities; an empty sandbox disables scripts and isolates the content from the host page.
srcdoc: An iframe attribute that renders an inline HTML string instead of loading a URL, keeping content local.
Rendered view: The visual output a browser produces from HTML and CSS.
Source view: The raw markup shown as escaped text so tags are read, not interpreted.

Frequently Asked Questions

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Why use HTML Viewer & Previewer?

See HTML rendered instantly without saving a file or spinning up a server
Sandboxed iframe with scripts disabled — safe to preview untrusted markup
Toggle between the rendered output and escaped, readable source
CSS styling is applied so you see a faithful preview of your page
Everything runs locally — your HTML never leaves the browser

Common use cases

Quickly check how an email or landing-page snippet renders before shipping it
Inspect scraped or exported HTML safely without running its scripts
Teach or learn HTML by editing markup and watching the result update
Verify CSS layout and styling on a fragment without a full project
Preview AI-generated HTML before pasting it into your codebase

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