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HTML Viewer

Free online HTML viewer and live preview — paste markup, beautify HTML, test mobile layout, and render pages in a sandboxed iframe. Nothing uploaded.

100% client-side — your data never leaves this tab

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What is HTML Viewer?

HTML Viewer is a free online HTML preview tool that renders markup in a live sandboxed iframe as you type. Paste a full page, a component fragment, or minified HTML from a CMS — then beautify it, copy the source, and check how it looks at mobile width (375px). Unlike upload-based preview services, your code never leaves the browser. Use it to prototype landing sections, debug email templates, clean up exported markup, or teach HTML with instant visual feedback.

HTML editing and preview rendering run entirely in your browser. Markup is never uploaded, stored, or logged on any server.

How to use HTML Viewer

  1. 1Paste or write HTML in the source editor on the left — full documents or snippets both work.
  2. 2Watch the live preview update on the right inside a sandboxed iframe.
  3. 3Click Beautify to re-indent tags into readable, copy-friendly markup.
  4. 4Switch to Mobile width to preview how the page looks on a narrow phone viewport.
  5. 5Toggle Allow scripts only when you trust the HTML and need JavaScript or interactive widgets.
  6. 6Use Sample to load a starter page, or Copy to grab the formatted source for your project.

Examples

HTML fragment (auto-wrapped)

Fragments without <!DOCTYPE html> are wrapped in a minimal document with charset and viewport meta tags.

<h1>Welcome</h1>
<p>A paragraph with <strong>bold</strong> and <em>italic</em> text.</p>
<ul>
  <li>First item</li>
  <li>Second item</li>
</ul>

Inline-styled email block

Common pattern for HTML email previews — table layout with inline CSS.

<table role="presentation" width="100%" style="max-width:600px;margin:0 auto">
  <tr>
    <td style="padding:24px;font-family:Arial,sans-serif">
      <h2 style="margin:0 0 12px">Your order shipped</h2>
      <p style="margin:0;color:#555">Track your package using the link below.</p>
    </td>
  </tr>
</table>

Component with embedded CSS

Embedded <style> blocks render in the preview. External stylesheets load if the URL is reachable.

<style>
  .card { border: 1px solid #ddd; border-radius: 8px; padding: 1rem; }
  .card h3 { margin-top: 0; }
</style>
<div class="card">
  <h3>Pricing</h3>
  <p>Pro plan — $19/mo</p>
</div>

Tips & common mistakes

  • Load the sample document first to see how a full page with CSS renders before pasting your own.
  • Keep Allow scripts off when previewing HTML from emails, tickets, or unknown sources.
  • Beautify works best on well-formed markup — unclosed tags may produce uneven indentation.
  • Use Mobile width to catch overflow, tiny tap targets, and fixed-width layout problems early.
  • For Markdown content, use the Markdown Previewer — this tool expects raw HTML input.

Who uses this tool?

  • Email marketers previewing newsletter HTML before sending through Mailchimp, SendGrid, or SES.
  • Frontend developers testing component markup copied from React, Vue, or Angular devtools.
  • Designers prototyping hero sections, pricing cards, and landing page blocks without a local server.
  • Students learning HTML and CSS with immediate visual feedback as they edit tags.
  • Support engineers reproducing customer-reported rendering issues from pasted page source.

Frequently asked questions

What is an online HTML viewer?
An online HTML viewer lets you paste HTML markup and see how a browser renders it without deploying to a server. This tool updates the preview live as you edit and runs entirely in your browser for privacy.
Can I preview a full HTML page or just a snippet?
Both. Full documents with <!DOCTYPE html> render as-is. Snippets and fragments are automatically wrapped in a minimal HTML shell that includes charset and viewport meta tags so they display correctly.
Why is JavaScript disabled by default?
The preview uses a sandboxed iframe without scripts by default to protect you from malicious pasted HTML. Enable Allow scripts when you intentionally need to test buttons, forms, or other interactive behavior in trusted markup.
Do external CSS, images, and fonts load in the preview?
External resources referenced by absolute URLs (https://…) may load if your browser allows network requests from sandboxed iframes. Relative paths and local file URLs will not resolve unless the resource is embedded inline.
How is this different from the Markdown Previewer?
HTML Viewer renders raw HTML directly. Markdown Previewer converts Markdown syntax (# headings, **bold**, code fences) into HTML first. Use HTML Viewer when you already have HTML; use Markdown Previewer when you write in Markdown.
Is my HTML uploaded to a server?
No. Source editing and iframe rendering happen 100% client-side. Your markup, email templates, and proprietary page source never leave your device.