CSS Variable Theme Previewer & Live Demo

Working with CSS custom properties unlocks dynamic theming, but repeatedly editing and refreshing your styles to test new color schemes is tedious. This tool changes the game by letting you paste an entire :root block of CSS variable definitions—think background, foreground, muted, accent colors—and apply them instantly to a live preview section. See text, buttons, and borders update in real time without touching your site’s stylesheet or rebuilding locally.

Whether you’re designing a blog theme, a client dashboard, or an interactive widget, you’ll save development time and eliminate guesswork. Just paste your variables like:

:root {
  --bg: #f9fafb;
  --fg: #111;
  --muted: #555;
}

Then click “Apply Theme” to watch your colors take effect immediately. Need to start over? Hit “Reset” to revert to default values. Built 100% client-side, this privacy-safe tool never sends your CSS anywhere. It’s fully mobile-friendly too, so you can prototype and tweak themes on the go.

Paste your :root CSS variables:

Live Preview

This is sample text demonstrating your --bg, --fg, and --muted colors.

How It Works

Paste your :root block into the textarea.
Click “Apply Theme” to inject a dynamic <style> tag with your variables.
See the preview section update instantly without a page reload.
Click “Reset” to remove your custom variables and return to defaults.
Use this workflow to prototype color schemes on mobile or desktop.

FAQ

Can I define any CSS variable? Yes—any custom property in your :root block will be applied.
Is my CSS stored? No. All processing is client-side; nothing is saved or transmitted.
What if I paste invalid CSS? The tool will ignore invalid lines but still apply valid declarations.
Can I test multiple themes? Yes—paste a new :root block and click “Apply Theme” again.