HTML Editor

Write HTML and CSS in the left panel, see the result on the right — no server, no build step, no browser extension. It's the same workflow as CodePen or JSFiddle but without an account wall when you just need a quick preview. Useful for testing a snippet you found online before putting it in a project, prototyping a layout idea in two minutes, or checking whether a CSS rule does what you think it does without touching your actual codebase.

The live preview renders inside a sandboxed iframe

Scripts run but they can't access the parent page. So if you're testing JavaScript that manipulates the DOM or fires fetch requests, it runs in isolation — your test won't interfere with anything else in your browser tab and vice versa. The sandbox attribute restricts access to things like localStorage, top-level navigation, and form submission to external URLs. That's intentional. It means pasting untrusted HTML snippets here to see what they do is reasonably safe — you're not running arbitrary code in the context of your own page. One thing the sandbox doesn't do is load external resources that require specific CORS headers. If you paste a snippet that tries to fetch from an API, it may fail not because your code is wrong but because the API doesn't allow requests from a sandboxed origin.