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Web Performance Optimization & Lighthouse · Lesson

Reducing Unused CSS

Find and eliminate dead CSS that bloats your stylesheets, using coverage tools, purging, and modular authoring to ship only the rules each page actually uses.

The Cost of Dead CSS

Large frameworks and accumulated styles often ship rules no page uses. Unused CSS inflates download size and parse time, and because CSS is render-blocking, it directly delays first paint.

Measuring Coverage

The DevTools Coverage tab records which CSS bytes actually apply during a session. A high unused percentage signals an opportunity to trim.

All lessons in this course

  1. Critical CSS and CSS Delivery
  2. Optimizing Font Loading
  3. CSS-in-JS Performance Impact
  4. Reducing Unused CSS
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