Designing Flawless Dark & Light Modes with CSS

Dark mode is no longer an optional theme—it is a core part of brand perception and accessibility. The key is to lead with semantics: define tokens, respect user preferences, and avoid one-off overrides when something feels misaligned.

• Start with design tokens mapped to CSS custom properties
• Honor prefers-color-scheme for first render
• Use a toggle that persists intent with localStorage
• Audit contrast for both themes before shipping

:root {
  color-scheme: light dark;
  --surface: #ffffff;
  --surface-inset: #f4f6fb;
  --text: #1f2933;
  --accent: #274690;
}

@media (prefers-color-scheme: dark) {
  :root {
    --surface: #101623;
    --surface-inset: #151d2d;
    --text: #f5f7fa;
    --accent: #5c8bff;
  }
}

body.theme--dark {
  --surface: #101623;
  --surface-inset: #151d2d;
  --text: #f5f7fa;
  --accent: #5c8bff;
}

By layering the system preference with a user-controlled toggle, you offer a flawless experience whether someone opens the page at noon or midnight.