P1Issue #49
Page speed : Reduce unused CSS
ā What does it mean?
ā What does it mean?
When a website loads, the browser downloads and parses all CSS files. Often, these stylesheets contain rules that are never applied to the current page (like styles for unused components, old libraries, or hidden elements).
This unused CSS:
Increases page size unnecessarily.
Delays First Contentful Paint (FCP) and Largest Contentful Paint (LCP).
Hurts Core Web Vitals and SEO performance.
šØ Why is it important for SEO?
šØ Why is this a problem for SEO?
Slower Page Speed ā Extra CSS increases render-blocking time.
Higher Bounce Rate ā Visitors leave if the page loads slowly.
Wasted Crawl Budget ā Search engines spend time on bloated assets.
Lower Rankings ā Google rewards fast, optimized websites.
ā How to Fix It
ā
Best Practices to Fix
Audit unused CSS using Chrome DevTools ā Coverage tab.
Remove dead CSS manually or with tools like PurgeCSS, UnCSS, or Tailwind JIT.
Use Critical CSS: inline only the CSS needed for above-the-fold content.
Split CSS by page (code-splitting) to avoid loading global styles everywhere.
Minify and compress CSS before deployment.
ā Bad Example
š Example
ā Bad (Bloated CSS file):
/* styles.css (200KB) */
.navbar { background: #fff; }
.footer { background: #000; }
.carousel { ... } /* Not used on homepage */
.chat-widget { ... } /* Not used at all */
š The homepage loads a 200KB CSS file, but only 50KB is needed.
ā Good Example
ā
Good (Optimized CSS with PurgeCSS):
/* homepage.css (50KB) */
.navbar { background: #fff; }
.footer { background: #000; }
š Only necessary styles are included. The page loads faster.
ā” Result
ā” SEO Impact of Fixing
Faster rendering and interaction ā better Core Web Vitals (FCP, LCP, INP).
Improved mobile experience on slow connections.
Higher chances of better Google rankings due to speed improvements.
ā Frequently Asked Questions
What is unused CSS?
Unused CSS refers to styles in your CSS files that are not applied to any elements on the current webpage, leading to unnecessary bloat.
Why is unused CSS bad for SEO?
Unused CSS increases page load times, delays key performance metrics like FCP and LCP, wastes crawl budget, and can lead to lower search rankings.
How can I identify and remove unused CSS from my website?
You can use tools like Chrome DevTools Coverage tab, PurgeCSS, UnCSS, or Tailwind JIT to audit and remove unused CSS from your stylesheets.
What are the benefits of reducing unused CSS?
Benefits include faster page rendering, improved Core Web Vitals scores, better mobile performance, and higher chances of ranking well in search engines.