Use when reviewing stylesheets, component styles, and responsive behavior related to Remove unused CSS rules. Check the rendered layout across breakpoints and interaction states before proposing a fix.
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---
name: unused-css
description: "Use when reviewing stylesheets, component styles, and responsive behavior related to Remove unused CSS rules. Check the rendered layout across breakpoints and interaction states before proposing a fix."
metadata:
category: css
priority: high
difficulty: intermediate
estimatedTime: "25"
source: frontendchecklist.io
url: https://frontendchecklist.io/rules/css/unused-css
---
# Remove unused CSS rules
Most projects use only 10-25% of their CSS—removing the rest can cut bundle sizes by 75%+ and dramatically improve load times.
## Quick Reference
- Use PurgeCSS or UnCSS to remove unused selectors
- Integrate into build pipeline (Webpack, Vite, PostCSS)
- Safelist dynamic classes and framework-specific patterns
- Typical reduction: 50-90% for CSS framework users
## Check
Use tools like PurgeCSS, UnCSS, or Chrome DevTools Coverage to identify and remove unused CSS to reduce bundle size and improve performance.
## Fix
Implement automated unused CSS removal in your build process and regularly audit CSS files to eliminate dead code and unused selectors.
## Explain
Explain how unused CSS bloats bundle sizes, slows page loading, and how modern tools can safely remove unused styles without breaking functionality.
## Code Review
Review stylesheets, component styles, and responsive states related to Remove unused CSS rules. 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/rules/css/unused-css
