HTML Viewer — Preview HTML

Paste HTML and see it rendered instantly, in a fully isolated preview panel — unlike a formatter, this doesn't change your code: it shows it exactly as a browser would.

The preview renders inside an isolated iframe (sandbox) that never executes JavaScript, whether or not your HTML has a <script> tag — it can't even access the rest of the page.

Local processing: your text is processed in your browser and never uploaded to Numelto.

Preview security

The HTML is never executed in Numelto's own context: the preview lives inside an <iframe sandbox="">, without the "allow-scripts" permission — the browser guarantees no <script> ever runs, no matter what HTML was pasted, and that iframe can't access this page or your data. As an extra layer, the HTML is also sanitized before being shown.

When to use it

Useful for quickly checking how an HTML fragment looks without creating a file or opening an editor, for reviewing HTML another tool generated, or for debugging an email template or a snippet before using it on a real site.

If what you need is to format the code (indent it), use the HTML formatter.

Frequently asked questions

Related tools

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