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name: css-minification description: "Use when reviewing stylesheets, component styles, and responsive behavior related to Minify all CSS files. 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/css-minification

Minify all CSS files

Unminified CSS wastes bandwidth with whitespace, comments, and verbose syntax—minification delivers the same styles in significantly fewer bytes.

Quick Reference

• Enable minification in build tool (Vite, webpack, etc.)
• Use cssnano or lightningcss for PostCSS pipelines
• Typical reduction: 20-40% file size savings
• Combine with Gzip/Brotli for maximum compression

Check

Verify that all CSS files are minified in production to reduce file size, eliminate whitespace, and improve page load performance.

Fix

Set up CSS minification in your build process using tools like cssnano, CleanCSS, or built-in framework minification to compress CSS files.

Explain

Explain how CSS minification improves website performance by reducing file sizes, decreasing bandwidth usage, and speeding up page load times.

Code Review

Review stylesheets, component styles, and responsive states related to Minify all CSS files. 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/css-minification