HTML Viewer Online

Write or paste a complete HTML document and preview it instantly.

JavaScript runs in an isolated preview and cannot access the parent page.

HTML

Ctrl/⌘ + Enter to run
Loading...

HTML Viewer Online for Live Browser Previews

An HTML viewer online lets you write or paste HTML and see the rendered result without creating a local project. This viewer also supports CSS and JavaScript inside the document, so you can test a complete page, a small component, or a quick experiment in one browser tab.

Your code stays in your browser. The preview runs in a sandboxed iframe with a separate origin, so scripts in the preview cannot read or modify the CleanCode Tools page.

How to View HTML Online

  1. Paste a complete HTML document or an HTML fragment into the editor.
  2. Select Run, or press Ctrl/Command + Enter, to render the current code.
  3. Enable Auto Preview when you want the result to update as you type.
  4. Switch between responsive width presets to check desktop, tablet, and mobile layouts.
  5. Open the preview in fullscreen when you need more room.
  6. Copy the source or download it as an HTML file when you are finished.

The Sample button loads a working document if you want to explore the viewer before adding your own code.

What You Can Test

HTML Structure

Check headings, paragraphs, links, lists, tables, forms, and semantic page sections. A simple document starts like this:

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <title>Preview example</title>
  </head>
  <body>
    <h1>Hello, world!</h1>
    <p>This page is running in the HTML viewer.</p>
  </body>
</html>

CSS and Responsive Layouts

Add a <style> element or inline styles to test spacing, colors, typography, Grid, and Flexbox. The viewport buttons change the preview width, which is useful for checking media queries. They simulate viewport size; they do not emulate a specific device or browser engine.

JavaScript

Scripts inside the document can update the preview and respond to user actions. They run with sandbox="allow-scripts", without allow-same-origin. This isolation prevents preview code from reaching the parent page, but you should still avoid pasting secrets or untrusted third-party code into any online editor.

Common HTML Preview Problems

  • The preview is blank: Run the preview again and check for missing closing tags or JavaScript that replaces the page content.
  • A stylesheet or image is missing: Confirm that its URL is public and uses HTTPS. Relative files from your computer are not uploaded with the document.
  • A script fails: Open your browser developer tools to inspect errors, and remember that sandboxed documents have intentional security restrictions.
  • Mobile styling looks unchanged: Include a viewport meta tag and make sure the CSS contains the expected media queries.
  • Your source is difficult to read: Use the HTML formatter before previewing it.

HTML Viewer, Editor, and Source Viewer

These terms often overlap. An HTML source viewer shows markup as text, while an HTML reader or renderer displays the page it describes. This tool combines an editor with a rendered browser preview, allowing you to change the source and immediately inspect the result.

Related Developer Tools

Feedback