HTML/CSS Playground
Write HTML, CSS, and JavaScript side by side, preview responsive widths, pop out a larger preview, and inspect console output locally.
Preview viewport: 100%
Feedback
Console output and runtime errors appear here.
Questions
Does the HTML/CSS Playground run JavaScript?
Yes. JavaScript runs inside the sandboxed preview frame so buttons and small interactions can be tested locally, with console output and runtime errors shown in the feedback panel.
Can I preview mobile and tablet widths?
Yes. Use the preview width controls to switch between desktop, tablet, and phone frames inline or in the larger popout preview.
Is my code uploaded?
No. The preview document is generated in this browser tab and nothing leaves your device.
Does Utilumo upload my input?
No. This tool is designed for local browser processing and does not send your input to a server.
Do I need an account?
No. Utilumo tools are built to work without accounts or sign-in.