Write Code, See Results Instantly
Test HTML, CSS, and JavaScript in a sandboxed browser environment. No signup, no upload, 100% private. AI cannot run your code - we provide real runtime execution.
Write HTML, CSS, and JavaScript in the code panels. Click Run to combine your code into a single HTML document and render it in the sandboxed preview iframe. All processing happens in your browser - nothing is uploaded.
Quickly prototype web pages, test CSS layouts, debug JavaScript functions, experiment with HTML APIs, or learn web development without setting up a local environment. AI cannot actually execute your code - this tool provides real runtime execution.
"My code snippet doesn't work - can you test it?" Most AI tools can only guess what your code does. This playground executes your actual HTML, CSS, and JavaScript in a real browser environment and shows you the exact rendered result.
Your code never leaves your browser. The preview iframe uses the sandbox attribute (allow-scripts only) so your code cannot access cookies, localStorage, or make network requests outside the sandbox. 100% private.
How the preview sandbox behaves
The preview is a real browser document in a sandboxed iframe, which is what makes it trustworthy — and it also explains a few things that look like bugs.
- The preview is isolated: it gets a fresh document and cannot read the editor page's cookies, localStorage or JavaScript variables.
- Nothing re-renders while you type. Press Run to combine the three panels into one document and render it.
- Relative URLs resolve against the preview document, not your project.
src="logo.png"will not find your project's image — use absolute URLs for images, CSS and scripts. - Scripts only run when they are inside
<script>tags. Plain JavaScript typed into the HTML panel is rendered as text. - The exported
.htmlfile contains exactly what the preview rendered, so it opens on its own with no dependencies beyond what you wrote. - Network requests from the preview happen in your browser: a CDN
<link>is fetched by you, never by us.
Frequently Asked Questions
Is the HTML Playground really free?
Yes. No signup, no credit card, no daily limits. Unlike CodePen's free tier (limited pens) or JSFiddle's pro features, this playground is entirely free with no usage caps. Everything runs in your browser.
Do I need to install anything?
No. The HTML playground runs entirely in your browser. No downloads, no extensions, no setup. Just open the page and start coding. Works on any device with a modern browser.
Is my code saved or stored anywhere?
No. Your code stays in your browser. Nothing is uploaded to any server. The preview is rendered in a sandboxed iframe that cannot access your personal data. Close the tab and everything is gone.
Can AI do what this tool does?
No. AI can generate code suggestions and snippets, but it cannot actually execute, render, or test code in a live browser environment. This tool provides real runtime execution with a sandboxed preview. You can see exactly how your HTML, CSS, and JavaScript will behave in a browser.
What can I build with this playground?
Prototype web pages, test CSS layouts and animations, debug JavaScript functions, experiment with HTML5 APIs (Canvas, Web Audio, Drag & Drop), create UI components, learn web development, and share code snippets.
Why does the preview use sandbox attribute?
The sandbox attribute (allow-scripts only) prevents your code from accessing cookies, localStorage, sessionStorage, and making network requests outside the sandbox. This keeps you safe while testing untrusted code snippets.
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