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name: embedded-or-inline-css description: "Use when reviewing stylesheets, component styles, and responsive behavior related to Avoid embedded and inline CSS. Check the rendered layout across breakpoints and interaction states before proposing a fix." metadata: category: css priority: high difficulty: beginner estimatedTime: "15" source: frontendchecklist.io url: https://frontendchecklist.io/rules/css/embedded-or-inline-css

Avoid embedded and inline CSS

Inline CSS cannot be cached separately, increases HTML payload, breaks separation of concerns, and is harder to maintain in large codebases.

Quick Reference

• Move inline styles to external CSS files or CSS-in-JS
• Exception: critical CSS should be inlined for performance
• Exception: dynamic values (CSS custom properties) can be inline
• Inline CSS breaks caching and increases HTML size

Check

Verify that inline CSS and embedded styles are avoided except for valid use cases like critical CSS, dynamic styles, or performance optimization.

Fix

Move inline and embedded CSS to external stylesheets, keeping only critical above-the-fold CSS inline for performance optimization.

Explain

Explain why external CSS is preferred for maintainability, caching, and separation of concerns, with exceptions for critical CSS and dynamic styles.

Code Review

Review stylesheets, component styles, and responsive states related to Avoid embedded and inline CSS. 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/embedded-or-inline-css