What is the CSS Playground?

A live sandbox for experimenting with HTML and CSS together. Edit either pane, and the preview iframe updates instantly. Useful for trying out new CSS features, debugging selectors, or building isolated component examples.

Is the preview sandboxed?

Yes — the preview runs in an iframe with the sandbox attribute restricting scripts and network access. Your code never leaves the browser; nothing is uploaded.

Can I import external fonts or CSS?

External @import or URLs are blocked by the sandbox. Paste the relevant CSS directly into the editor, or use system fonts for previews.

CSS Playground

Reset styles

Viewport meta

HTML

CSS

Preview

Technical details

How the CSS Playground Works

What the Tool Does

The CSS Playground gives you two editors — HTML and CSS — and a sandboxed iframe preview that updates as you type. Use it to prototype components, test selectors, validate fallback styles, or build minimal repros for bug reports. The 'Reset styles' toggle adds a small CSS reset (box-sizing, sensible body defaults) so your CSS isn't fighting browser defaults.

Common Developer Use Cases

Frontend developers build isolated component examples to share in pull requests or documentation. Designers experiment with gradients, shadows, animation timings, and modern features like grid, subgrid, and container queries. Educators demo CSS concepts to students without spinning up CodePen accounts. QA engineers reproduce CSS-only bugs cleanly in a controlled environment.

Data Formats, Types, or Variants

The HTML editor accepts any body content. The CSS editor accepts any modern CSS — custom properties, nesting, @container, @layer, etc. Output is a full standalone HTML document with the meta viewport tag (optional) and an inline style block, ready to copy as a complete file. The preview iframe uses sandbox='allow-same-origin' to permit relative URLs while blocking scripts and form submissions.

Common Pitfalls and Edge Cases

External @font-face URLs and @import statements may be blocked by the iframe sandbox. Pasting CSS that depends on inherited styles from an outer document won't behave the same here because the iframe is isolated. Animations with very long durations continue running in the preview iframe even when the editor is not focused; pause them with animation-play-state if you're debugging timing.

When to Use This Tool vs Code

Use the browser tool for one-shot experiments, isolated minimal reproductions, or quick teaching demos. In a real project, your dev server, hot module replacement, and component devtools (React Refresh, Vue devtools) give you a much richer feedback loop — use this playground for sketches that you don't want to set up tooling for.