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 90% (1.6s median) compared with 98% (1.1s median) under 140 KB.

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

20.3% of Shopify sites use under 140 KB of unused CSS unused CSS bytes, and 98% of those sites have a good LCP, against 96% of all Shopify sites.

The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 8,062 with all devices 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 under 140 KB of unused CSS unused CSS bytes have a good LCP most often: 98%, against 96% of all Shopify sites. Sites with over 600 KB of unused CSS unused CSS have it least often, at 90%.

SitesGood, needs improvement, poor LCPMedian
All Shopify sites8,06296%1.3s
Under 140 KB unused 20.3%1,62298%1.1s
140 to 300 KB unused 37.6%3,03198%1.3s
300 to 600 KB unused 32.1%2,59695%1.5s
Over 600 KB unused 10.0%80890%1.6s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 8,062 with all devices 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. Under 140 KB of unused CSS is 20.3% 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 · 8,062 with all devices 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 under 140 KB of unused CSS and over 600 KB of unused CSS sits in element render delay: 201 ms median for under 140 KB of unused CSS against 415 ms for over 600 KB of unused CSS. Overall median field LCP is 1.1s for under 140 KB of unused CSS (TTFB 354 ms, load delay 507 ms, load duration 214 ms, render delay 201 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 6,987389 ms589 ms208 ms298 ms589 mslab 589 ms1.3s
Under 140 KB unused 1,384354 ms507 ms214 ms201 ms507 mslab 507 ms1.1s
140 to 300 KB unused 2,607381 ms567 ms219 ms273 ms567 mslab 567 ms1.3s
300 to 600 KB unused 2,276405 ms649 ms199 ms368 ms649 mslab 649 ms1.5s
Over 600 KB unused 720428 ms719 ms415 ms719 mslab 719 ms1.6s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 8,062 with all devices 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 94% of jQuery sites have a good LCP, against 96% of all sites. On Vue, 42% of sites use 300 to 600 KB of unused CSS, and 95% 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%96%
Vue 933 sites300 to 600 KB unused 42%140 to 300 KB unused 33%Over 600 KB unused 17%95%
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%94%
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 · 8,062 with all devices 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 under 140 KB of unused CSS unused CSS bytes have a good LCP, against 97% of jQuery sites with 140 to 300 KB of unused CSS. Within jQuery, sites with under 140 KB of unused CSS and 140 to 300 KB of unused CSS have a good LCP about equally often. On Vue, 93% of sites with under 140 KB of unused CSS unused CSS bytes have a good LCP, against 99% of Vue sites with 140 to 300 KB of unused CSS. Within Vue, 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 1,675 sites (20.3%) with under 140 KB of unused CSS, 98% pass field LCP at a 1.1s median, whereas the 10.0% (821) over 600 KB drop to 90% good LCP (1.6s median).

The State of Web Vitals · October 2026 · Shopify: 8,246 crawled sites · 8,062 with all devices 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, 1.1s median) versus 10.0% above 600 KB (90% 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 · 8,062 with all devices 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 (8,062 with all devices Chrome field data, 8,241 sites with unused CSS bytes, October 2026) · How we measured