How to Preview HTML and Inline CSS Live in a Sandboxed Iframe Without Saving Files
Learn how to type or paste HTML into the editor, see it rendered immediately in an isolated iframe, and understand what the sandbox allows.
HTML Live Preview
Introduction
Checking a small HTML fragment normally means creating a file, opening it in a browser and refreshing after every edit. HTML Live Preview renders the editor contents in an iframe on every keystroke, so markup and inline styles can be checked as they are typed. The page runs entirely in the browser and nothing is sent to a server.
Step-by-Step Instructions
- Replace the sample markup in the HTML Source Code box with the HTML to test.
- Watch the Live Browser Preview panel on the right, which re-renders as soon as the source changes.
- Add inline style attributes or a style block inside the source to check CSS alongside the markup.
- Include a script tag if JavaScript behaviour needs to run; scripts are permitted inside the sandbox.
- Select the source text and copy it from the editor when the fragment is ready for the real page.
Key Use Cases
- Email Snippets: Check how a table-based email block renders before dropping it into a campaign tool.
- CMS Embeds: Verify a third-party embed snippet produces visible output before saving it in a content block.
- Teaching Demos: Show the effect of a single attribute change on the rendered element in real time.
Frequently Asked Questions
Is the preview isolated from the rest of the page?
Yes. The preview is an iframe with sandbox set to allow-scripts only, so the content runs in a separate origin with no access to the host page, its cookies or its storage. Form submission, pop-ups and top-level navigation are blocked by the sandbox.
Does the editor need a full HTML document?
No. The source is passed to the iframe as a document, so a fragment such as a single div with inline styles renders fine. A complete document with head and body also works, and style tags are applied normally.
Is there a copy or download button?
No. This tool is a viewer only; the source stays in the editor textarea, so copy it from there. The preview panel is fixed at 400px tall and scrolls when the content is longer.