HTML · no setup, no account
Paste the page.
Watch it run.
CodeRush is an HTML playground with nothing in front of it. Drop in a complete document or a loose fragment, and the pad detects what you gave it, renders it in a sandboxed frame, and leaves you in the editor beside the result.
- Runs the moment you paste
- Sandboxed frame
- Source stays in your browser
A document or a fragment
The detector decides, and tells you what it found.
A full page with <!doctype html>, <head> and <body> runs exactly as written: your styles, your scripts, your markup, nothing wrapped around it. A bare fragment — one <section>, a table, a form — gets a minimal host document so it has somewhere to live.
You never pick a language from a menu. The pad sniffs the source, shows the kind it chose on the source badge, and can say why it chose it. If you paste CSS, Markdown or JSON into the same box, it switches to the right renderer instead of failing.
<!doctype html>
<title>Follow your what if</title>
<h1>There's something here.</h1>
<p>Edit this line in the pad, press Run, and the preview follows.</p>That link carries the four lines above after the URL's #. Browsers never send a fragment in a request, so the snippet reaches the pad without touching a server.
What the preview can and cannot reach
The boundary is the product, not a setting.
Your page renders inside an iframe with allow-scripts and without allow-same-origin, so it has an opaque origin. It cannot read the pad around it, your snapshot history, or anything else in the browser. The pad cannot read inside it either; the two sides exchange messages, never documents.
Images, fonts and scripts from another host pause before their first request, naming the origin, so a pasted page cannot quietly call home. Run offline keeps the HTML and inline CSS visible with no scripts, forms, popups or connections at all — useful when the page came from somewhere you have not read yet.
If a render goes quiet, the pad stops the frame, keeps your source, and offers the offline retry. Inline loops carry a three-second budget that resets whenever the page yields, so a runaway while loop ends up as a message rather than a dead tab.
Then keep it, or pass it on
Three exits, all of them local first.
Name a snapshot and it lives in this browser, up to 24 of them, pinnable and exportable as one JSON file. Restoring a snapshot first checkpoints whatever was in the pad and offers Undo, so opening an old sketch cannot eat the current one.
Download the exact source when you want a file. Create a Rush link when you want someone else to see it run: public, private or password-protected, with the source in the fragment rather than in a database.
Split view puts source and result side by side. Twelve templates and thirty-two demos — three.js scenes and games — give you a working page to start from, and the guide walks the whole loop in three moves.
Questions
- Do I need an account to run HTML here?
- No. There is no sign-up, no profile and no saved cloud project. The page is static files; the work happens in your browser.
- Can I paste a fragment instead of a whole page?
- Yes. A fragment such as a single section or form is given a minimal host document so it renders on its own.
- Where does my HTML go?
- Into the editor and into the sandboxed frame, both inside your tab. The pad never posts your source to a CodeRush server; see the privacy notes for the exact boundaries.
- Does the preview run my JavaScript?
- Yes, immediately, in the sandbox. Turn on Review code before it runs from the command palette and pages with scripts or outside connections wait for you first.