Paste your :root { } block with CSS custom properties
Dark mode output will appear here
Paste your CSS variables and click Generate// generate dark mode @media blocks from css variables
Generate @media prefers-color-scheme dark blocks from your CSS variables. Instantly convert light theme tokens to dark mode overrides. Free, browser-based, no sign-up.
Dark mode output will appear here
Paste your CSS variables and click GenerateCopy your :root {} block containing CSS custom properties into the input field.
Click Generate Dark Mode. The tool extracts all --variables and builds editable dark override rows.
Tweak any dark value inline, then copy the final @media block ready to paste into your stylesheet.
The CSS Dark Mode Generator reads your light theme CSS custom properties and creates an @media (prefers-color-scheme: dark) block with all your variables ready to edit. No manual copy-pasting of every variable name.
prefers-color-scheme: dark?It's a CSS media feature that detects if the user's OS is set to dark mode. By wrapping overrides in @media (prefers-color-scheme: dark) { }, browsers automatically apply dark styles when the user prefers them — no JavaScript needed.
Not if you use CSS custom properties. You only need to override the variable values inside the media query — your component styles stay unchanged since they reference the variables, which now resolve to dark values automatically.
Enabling this option filters out variables whose values don't look like color values (hex codes, rgb(), hsl(), named colors). Spacing, font-size, and other non-color tokens are excluded since they typically don't need dark mode overrides.
Yes. A common pattern is to use prefers-color-scheme as the default and add a [data-theme="dark"] selector for a JS toggle. You can copy this tool's output into both selectors for full coverage.
No — everything runs entirely in your browser. Your CSS never leaves your machine. This tool uses client-side JavaScript to parse and generate the output, so your code stays private.
This tool is designed for standard CSS custom properties (--variable-name syntax). SCSS $variables and Less @variables use different syntax and are not currently supported.
A CSS Dark Mode Generator automates the most tedious part of implementing dark mode: creating the @media (prefers-color-scheme: dark) block with all your custom property overrides. Instead of manually copying every variable name and guessing dark equivalents, this tool parses your existing light theme CSS, extracts every custom property, and scaffolds a complete dark mode block ready for you to fill in or fine-tune.
Modern dark mode implementation with CSS custom properties follows a simple but repetitive pattern. You define all your colors as --variables in :root, then inside a dark media query, you redefine those same variable names with dark-appropriate values. This generator handles the boilerplate so you can focus on choosing the right dark colors.
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The cleanest modern approach uses two techniques together: CSS custom properties (variables) and the prefers-color-scheme media query. Here's a minimal example of the pattern:
:root {
--bg: #ffffff;
--text: #1a1a1a;
--primary: #3b82f6;
}
@media (prefers-color-scheme: dark) {
:root {
--bg: #0e0e0e;
--text: #f0f0f0;
--primary: #60a5fa;
}
}Because your components reference var(--bg) instead of hardcoded colors, they automatically update when the media query kicks in. No JavaScript, no class toggling — the browser handles it natively.
There are several approaches to dark mode: separate stylesheets, class-based toggling, JavaScript-driven theming, and CSS custom properties with media queries. The custom properties approach has become the industry standard for several reasons:
[data-theme] attribute, without touching component CSS.Generating the media block is the easy part. Choosing the right dark values takes more thought. A few principles that help:
#0d0d0d to #1e1e1e.For production sites, you often want to respect system preference by default but also let users override it. The cleanest pattern uses a data-theme attribute on <html> combined with the media query:
/* System default */
@media (prefers-color-scheme: dark) {
:root:not([data-theme="light"]) {
--bg: #0e0e0e;
--text: #f0f0f0;
}
}
/* Manual override */
[data-theme="dark"] {
--bg: #0e0e0e;
--text: #f0f0f0;
}This way, users without a preference see light mode, users with dark OS preference see dark mode automatically, and any user can override with a toggle that sets the attribute via JavaScript.
Even with the right technical approach, dark mode implementations often have issues. Watch out for hardcoded colors scattered through component CSS that weren't tokenized into variables — these won't respond to your variable overrides. Images with white backgrounds look bad on dark UIs; consider using mix-blend-mode: multiply or serving separate dark assets. Third-party embeds and iframes won't respect your theme unless they implement their own dark mode support.
Another frequent oversight is forgetting <meta name="color-scheme" content="light dark"> in your HTML head. This tells the browser to render built-in UI elements (scrollbars, form controls, etc.) in the appropriate scheme, matching your custom dark theme more naturally.