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name: dark-mode-css description: "Use when reviewing stylesheets, component styles, and responsive behavior related to Support dark mode with prefers-color-scheme. Check the rendered layout across breakpoints and interaction states before proposing a fix." metadata: category: css priority: medium difficulty: intermediate estimatedTime: "25" source: frontendchecklist.io url: https://frontendchecklist.io/rules/css/dark-mode-css

Support dark mode with prefers-color-scheme

More than half of users prefer dark mode for reduced eye strain, especially in low-light environments. Users with photosensitivity rely on it. Implementing dark mode via prefers-color-scheme respects the user's OS preference without them needing to find a toggle, and CSS custom properties make it a clean, maintainable addition rather than a disruptive refactor.

Quick Reference

• Use @media (prefers-color-scheme: dark) to apply dark mode styles
• Define light/dark colors as CSS custom properties on :root for easy switching
• Support a manual toggle by storing preference in localStorage and setting a data-theme attribute
• Ensure dark mode colors maintain WCAG contrast ratios

Check

Check if this CSS supports dark mode. Look for prefers-color-scheme usage or a data-theme attribute pattern. Identify any hard-coded colors that would look wrong in dark mode.

Fix

Implement dark mode by extracting colors to CSS custom properties and redefining them inside a prefers-color-scheme: dark media query.

Explain

Explain how to implement dark mode with CSS custom properties, the prefers-color-scheme media query, and a JavaScript toggle for user preference.

Code Review

Review stylesheets, component styles, and responsive states related to Support dark mode with prefers-color-scheme. Flag exact selectors, declarations, or breakpoints that violate the rule in the rendered UI.

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/rules/css/dark-mode-css