HTML Viewer

About the HTML Viewer

Paste a full page or a fragment and watch it render as you type: source with line numbers and highlighting on the left, the live page on the right. The preview runs in a sandboxed frame with no access to this site, and external fonts, images and scripts in your HTML load normally.

How to use the HTML Viewer

1. Paste HTML into the editor on the left, or click Sample to start from an example page.
2. The preview on the right updates as you type. Turn off Auto-preview and use Refresh if you prefer.
3. Use Copy or Download to take the HTML with you when it looks right.
4. Nothing is uploaded: the page is rendered locally inside an isolated frame.

Step-by-step walkthrough with examples and the errors people hit: How to Preview HTML Online Safely.

Example

A fragment is enough

<h1>Hello</h1>
<p>Rendered on the right.</p>

A live page showing the heading and paragraph, re-rendered on every edit.

Common errors and how to fix them

More problems and fixes in the tutorial

A live preview as you type

Paste or write HTML on the left and see it rendered on the right. With Auto-preview on, the page re-renders a quarter of a second after you stop typing; turn it off and press Refresh preview or Ctrl+Enter when you want control. Full screen gives the editor and the preview the whole window, which is what a real template needs.

What runs inside the preview

A complete document or a fragment both work. Inline CSS and JavaScript run, and external stylesheets, fonts, images and scripts from CDNs load, so a snippet that depends on Bootstrap or Tailwind renders correctly. The preview runs inside a sandboxed frame with an opaque origin: it has no cookies, no storage and no access to this site, so pasting HTML you did not write is safe.

Where an HTML viewer helps

Checking an email template before it goes into the sending system. Seeing what a snippet from a ticket or a Stack Overflow answer actually does. Previewing HTML generated by a script or a CMS without deploying it. Learning HTML and CSS with immediate feedback. In each case you want to look, not to build a project.

Copy, download and share

Copy HTML puts the source on your clipboard; Download .html saves it as a file you can open in any browser. To show the page to a colleague, paste the source into Log Share for an expiring link, or open a Private Room if only they should see it.

Viewer, editor, tester, validator

An HTML viewer renders code so you can see it; an online HTML editor adds writing conveniences; a tester adds a console; a validator checks the markup against the standard without rendering it. This page is a viewer and editor with syntax highlighting. For strict validation, run the source through the W3C validator once it looks right here.

FAQ