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CSS Minification

Testing & Quality
css-minification

CSS Minification is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

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.

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QUICK START

How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy and paste the prompt below.
  3. Review files and risks before approving any action.
Prompt to paste
Inspect the Agent Skill at https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/css-minification/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/css-minification, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

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.

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

Rule page: https://frontendchecklist.io/en/rules/css/css-minification