The State of Web Vitals

Shopify unused CSS bytes and the Core Web Vitals

10.0% of audited sites (821) parse over 600 KB of unused CSS rules before first paint, passing LCP at 92% (1.6s median) compared with 98% (1.0s median) under 140 KB.

Field data PhoneDesktopAll Scope All sites October 2026 edition · Desktop field outcomes · Shopify sites only
Shopify Scoped to 8,248 sites out of 203,892 analyzed (cms) Compare with all sites →

37.6% of Shopify sites use 140 to 300 KB of unused CSS unused CSS bytes, and 99% of those sites have a good LCP, against 97% of all Shopify sites.

The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP pass rate

Sites with 140 to 300 KB of unused CSS unused CSS bytes have a good LCP most often: 99%, against 97% of all Shopify sites. Sites with over 600 KB of unused CSS unused CSS have it least often, at 92%.

SitesGood, needs improvement, poor LCPMedian
All Shopify sites3,81897%1.3s
140 to 300 KB unused 37.6%1,24699%1.2s
Under 140 KB unused 20.3%57298%1.0s
300 to 600 KB unused 32.1%1,45496%1.3s
Over 600 KB unused 10.0%54492%1.6s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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Unused CSS bytes usage

140 to 300 KB of unused CSS is the most used: 37.6% of Shopify sites.

140 to 300 KB unused 37.6% 300 to 600 KB unused 32.1% Under 140 KB unused 20.3%
140 to 300 KB unused 37.6% 300 to 600 KB unused 32.1% Under 140 KB unused 20.3% Over 600 KB unused 10.0%
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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The four LCP phases

Across the four LCP sub-parts in Chrome's field data, the largest gap between 140 to 300 KB of unused CSS and over 600 KB of unused CSS sits in resource load delay: 585 ms median for 140 to 300 KB of unused CSS against 765 ms for over 600 KB of unused CSS. Overall median field LCP is 1.2s for 140 to 300 KB of unused CSS (TTFB 302 ms, load delay 585 ms, load duration 161 ms, render delay 275 ms) versus 1.6s for over 600 KB of unused CSS.

Median LCP phase breakdown (Chrome field p75) Load delay Median LCP
Shopify sites with unused CSS bytes 3,125305 ms630 ms304 ms630 mslab 620 ms1.3s
Under 140 KB unused 456286 ms542 ms217 ms542 mslab 548 ms1.1s
140 to 300 KB unused 1,006302 ms585 ms275 ms585 mslab 581 ms1.2s
300 to 600 KB unused 1,203312 ms676 ms339 ms676 mslab 663 ms1.4s
Over 600 KB unused 460331 ms765 ms373 ms765 mslab 733 ms1.6s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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Unused CSS bytes per framework

On jQuery, 37% of sites use 300 to 600 KB of unused CSS unused CSS bytes, and 95% of jQuery sites have a good LCP, against 97% of all sites. On Vue, 42% of sites use 300 to 600 KB of unused CSS, and 97% of Vue sites have a good LCP.

FrameworkUnused CSS bytes on its sitesGood LCP
Shopify sites with unused CSS bytes 8,241 sites140 to 300 KB unused 38%300 to 600 KB unused 32%Under 140 KB unused 20%97%
Vue 933 sites300 to 600 KB unused 42%140 to 300 KB unused 33%Over 600 KB unused 17%97%
jQuery 3,149 sites300 to 600 KB unused 37%140 to 300 KB unused 32%Over 600 KB unused 16%Under 140 KB unused 15%95%
140 to 300 KB unused 300 to 600 KB unused Under 140 KB unused Over 600 KB unused
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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Unused CSS bytes or the framework

Does the framework explain the unused CSS bytes difference?

On jQuery, 98% of sites with 140 to 300 KB of unused CSS unused CSS bytes have a good LCP, against 95% of jQuery sites with 300 to 600 KB of unused CSS. Within jQuery, sites with 140 to 300 KB of unused CSS and 300 to 600 KB of unused CSS have a good LCP about equally often. On Vue, 98% of sites with 140 to 300 KB of unused CSS unused CSS bytes have a good LCP, against 97% of Vue sites with 300 to 600 KB of unused CSS. Within Vue, sites with 140 to 300 KB of unused CSS and 300 to 600 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 1,675 sites (20.3%) with under 140 KB of unused CSS, 98% pass field LCP at a 1.0s median, whereas the 10.0% (821) over 600 KB drop to 92% good LCP (1.6s median).

The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy Arjen Karel · corewebvitals.io/state-of-cwv
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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, 20.3% stay under 140 KB of unused CSS (98% good LCP, 1.0s median) versus 10.0% above 600 KB (92% good LCP, 1.6s median).

Go fix it Remove unused CSS → Eliminate render-blocking resources →
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 3,818 with desktop field data · 8,241 sites with unused CSS bytesBy 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 · 8,246 crawled Shopify sites (3,818 with desktop Chrome field data, 8,241 sites with unused CSS bytes, October 2026) · How we measured