Unused CSS on the page: Crawl Audit check 84

Short answer: many sites load one big stylesheet on every page, full of rules for pages the visitor isn't on. The browser still has to download and read all of it before showing anything. Check 84 warns when PageSpeed estimates 20KB or more of unused CSS on the page.

What Crawl Audit checks

• Full report: Lighthouse's unused CSS audit. Pass if the total possible saving is under 20KB; warning at 20KB or more.
• Free check: this needs PageSpeed, so it passes with a note that full data needs PageSpeed.

The 20KB total is Crawl Audit's own line. Lighthouse lists each stylesheet with "a potential savings of 2 KiB or more."

What Google says

Lighthouse: "By default, a browser must download, parse, and process all external stylesheets that it encounters before it can display, or render, any content to a user's screen."

On devmarde.com

PageSpeed passed "Reduce unused CSS" for our homepage on 3 October.

How to cut it down

• Remove styles for features you no longer use: old sliders, retired plugins, unused theme parts.
• Split CSS so each page loads only what it needs. Frameworks with per-component CSS do this for you.
• Don't load a whole icon or UI library for a few pieces.

Some "unused" CSS is for things that appear later, such as menus opening or form errors. Don't delete a rule just because the first load didn't use it.

Sources

• Chrome for Developers, Remove unused CSS, checked 3 October 2026.