The State of Web Vitals

Unused CSS bytes on Wix sites

11.1% of audited sites (625) parse over 600 KB of unused CSS rules before first paint, passing LCP at 87% (1.5s median) compared with 97% (1.0s median) under 140 KB.

Field data PhoneDesktopAll Scope All sites October 2026 edition · All devices field outcomes · Wix sites only
Wix Scoped to 5,623 sites out of 203,892 analyzed (cms) Compare with all sites →

33.8% of Wix sites use under 140 KB of unused CSS unused CSS bytes, and 97% of those sites have a good LCP, against 94% of all Wix sites.

The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP pass rate

Sites with under 140 KB of unused CSS unused CSS bytes have a good LCP most often: 97%, against 94% of all Wix sites. Sites with over 600 KB of unused CSS unused CSS have it least often, at 87%.

SitesGood, needs improvement, poor LCPMedian
All Wix sites5,33394%1.2s
Under 140 KB unused 33.8%1,79597%1.0s
140 to 300 KB unused 31.0%1,65196%1.2s
300 to 600 KB unused 24.1%1,29491%1.3s
Over 600 KB unused 11.1%59387%1.5s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Unused CSS bytes usage

Under 140 KB of unused CSS is the most used: 33.8% of Wix sites.

Under 140 KB unused 33.8% 140 to 300 KB unused 31.0% 300 to 600 KB unused 24.1% Over 600 KB unused 11.1%
Under 140 KB unused 33.8% 140 to 300 KB unused 31.0% 300 to 600 KB unused 24.1% Over 600 KB unused 11.1%
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
3

The four LCP phases

Across the four LCP sub-parts in Chrome's field data, the largest gap between under 140 KB of unused CSS and over 600 KB of unused CSS sits in resource load delay: 398 ms median for under 140 KB of unused CSS against 549 ms for over 600 KB of unused CSS. Overall median field LCP is 1.1s for under 140 KB of unused CSS (TTFB 389 ms, load delay 398 ms, load duration 119 ms, render delay 158 ms) versus 1.5s for over 600 KB of unused CSS.

Median LCP phase breakdown (Chrome field p75) Load delay Median LCP
All Wix sites 3,945419 ms455 ms455 mslab 455 ms1.2s
Under 140 KB unused 1,303389 ms398 ms158 ms398 mslab 398 ms1.1s
140 to 300 KB unused 1,240407 ms447 ms447 mslab 447 ms1.2s
300 to 600 KB unused 965472 ms501 ms163 ms501 mslab 501 ms1.3s
Over 600 KB unused 437517 ms549 ms181 ms549 mslab 549 ms1.5s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
4

Unused CSS bytes per framework

On React, 34% of sites use under 140 KB of unused CSS unused CSS bytes, and 94% of React sites have a good LCP, against 94% of all sites.

FrameworkUnused CSS bytes on its sitesGood LCP
All Wix sites 5,621 sitesUnder 140 KB unused 34%140 to 300 KB unused 31%300 to 600 KB unused 24%Over 600 KB unused 11%94%
React 5,620 sitesUnder 140 KB unused 34%140 to 300 KB unused 31%300 to 600 KB unused 24%Over 600 KB unused 11%94%
Under 140 KB unused 140 to 300 KB unused 300 to 600 KB unused Over 600 KB unused
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
5

Unused CSS bytes or the framework

Does the framework explain the unused CSS bytes difference?

On React, 97% of sites with under 140 KB of unused CSS unused CSS bytes have a good LCP, against 96% of React sites with 140 to 300 KB of unused CSS. Within React, sites with under 140 KB of unused CSS and 140 to 300 KB of unused CSS have a good LCP about equally often.

Why unused CSS slows both network transfer and style calculation

Browsers must match every selector in the CSSOM against the DOM tree during layout and style recalculation. Across 1,901 sites (33.8%) with under 140 KB of unused CSS, 97% pass field LCP at a 1.0s median, whereas the 11.1% (625) over 600 KB drop to 87% good LCP (1.5s median).

The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
6

Understanding unused CSS bytes

Compile per-template CSS or run PurgeCSS/Tailwind content scanning so pages do not block first paint on hundreds of kilobytes of unreferenced selectors. Across all audited sites, 33.8% stay under 140 KB of unused CSS (97% good LCP, 1.0s median) versus 11.1% above 600 KB (87% good LCP, 1.5s median).

Go fix it Remove unused CSS → Eliminate render-blocking resources →
The State of Web Vitals · October 2026 · Wix: 5,621 crawled sites · 5,333 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
Related signals Iframes per page → Image fetchpriority → Responsive image markup → Script coverage (used vs unused) → By Arjen Karel · 5,621 crawled Wix sites (5,333 with all devices Chrome field data, October 2026) · How we measured