First-party vs third-party stylesheets and the Core Web Vitals
99.3% of audited sites (197,620) serve first-party stylesheets (86% good LCP, 1.4s median), while the 56.1% (111,639) loading external third-party stylesheets drop to 85% good LCP (1.4s median).
99.3% of sites use first-party stylesheets stylesheet origin (first-party vs third-party), and 86% of those sites have a good LCP, against 86% of all sites.
LCP pass rate
Sites with first-party stylesheets stylesheet origin (first-party vs third-party) have a good LCP most often: 86%, against 86% of all sites. Sites with third-party stylesheets CSS origin have it least often, at 85%.
Stylesheet origin (first-party vs third-party) usage
First-party stylesheets is the most used: 99.3% of sites.
LCP phase breakdown for first-party and third-party stylesheets
Across the four LCP sub-parts in Chrome's field data, the largest gap between first-party stylesheets and third-party stylesheets sits in resource load delay: 274 ms median for first-party stylesheets against 306 ms for third-party stylesheets. Overall median field LCP is 1.4s for first-party stylesheets (TTFB 572 ms, load delay 274 ms, load duration 110 ms, render delay 192 ms) versus 1.4s for third-party stylesheets.
Understanding first-party vs third-party stylesheets
How cross-origin CSS files add DNS and TLS round-trips to the critical rendering path
Because external stylesheets block rendering by default, fetching a CSS file from a third-party domain (such as fonts.googleapis.com, cdnjs, or a widget CDN) stalls first paint behind a fresh DNS lookup, TCP handshake, and TLS negotiation. Across 197,620 sites (99.3%) with first-party CSS, good LCP is 86% (1.4s median), whereas across 111,639 sites (56.1%) with third-party CSS, good LCP drops to 85% (1.4s median).
Copy external font and icon stylesheets (Google Fonts, Font Awesome, Bootstrap CDN) into your own build pipeline or origin server so every render-blocking CSS file shares the primary HTTP/2 or HTTP/3 connection. Across all audited sites, 99.3% use first-party CSS (86% good LCP) and 56.1% load third-party CSS (85% good LCP).
How stylesheet origin (first-party vs third-party) plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,503 sites 59.6% of WordPress sites load third-party CSS (74% good LCP vs 76% on first-party CSS).
Across 65,503 WordPress sites, 100.0% load first-party stylesheets (76% good LCP, 1.7s median) and 59.6% load external third-party stylesheets (74% good LCP, 1.8s median).
Shopify 8,570 stores 99.9% of Shopify stores serve first-party CSS (97% good LCP) and 78.0% load cross-origin CSS (96%).
Across 8,570 Shopify storefronts, 99.9% load first-party stylesheets (97% good LCP, 1.3s median) and 78.0% load cross-origin stylesheets (96% good LCP).
React & Next.js 9,569 sites React & Next.js sites loading third-party stylesheets (44.7%) pass LCP 6 points less often than sites on first-party CSS (73% vs 79%).
Across 9,569 React sites, 99.9% serve first-party CSS (79% good LCP, 1.5s median) and 44.7% load external third-party stylesheets (73% good LCP, 1.7s median).
By Arjen Karel · 210,902 crawled sites (69,745 with desktop Chrome field data, 198,997 sites with stylesheet origin (first-party vs third-party), October 2026). How we measured.