Subresource network protocols (HTTP/2, HTTP/3, HTTP/1.1) and the Core Web Vitals
HTTP/2 (92.5%), HTTP/3 QUIC (70.9%), and legacy HTTP/1.1 (68.2%) across all page subrequests: how connection protocols move Largest Contentful Paint.
92.5% of sites use HTTP/2 subresource network protocols, and 86% of those sites have a good LCP, against 86% of all sites.
LCP pass rate
Sites with HTTP/2 subresource network protocols have a good LCP most often: 86%, against 86% of all sites. Sites with HTTP/1.1 network protocols have it least often, at 85%.
Subresource network protocols usage
HTTP/2 is the most used: 92.5% of sites.
How subresource network protocols affect the four LCP phases
Across the four LCP sub-parts in Chrome's field data, the largest gap between HTTP/2 and HTTP/1.1 sits in resource load delay: 278 ms median for HTTP/2 against 302 ms for HTTP/1.1. Overall median field LCP is 1.4s for HTTP/2 (TTFB 579 ms, load delay 278 ms, load duration 111 ms, render delay 194 ms) versus 1.4s for HTTP/1.1.
Understanding subresource network protocols
Why most pages mix HTTP/2, HTTP/3, and HTTP/1.1 in a single load
While a page's HTML document uses a single connection, its subresources come from first-party CDNs, font hosts, and third-party scripts. Across 189,798 sites, 92.5% load subresources over HTTP/2 (86% good LCP), 70.9% negotiate HTTP/3 on at least one origin (85% good LCP), and 68.2% still make at least one legacy HTTP/1.1 request (85% good LCP).
Serve all first-party static assets over HTTP/2 and HTTP/3 via a modern CDN, and audit third-party scripts or unproxied asset hosts that still fall back to HTTP/1.1 (68.2% of sites). HTTP/1.1 origins cannot multiplex concurrent requests over a single connection, adding head-of-line blocking when multiple assets share that domain.
How subresource network protocols plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,509 sites WordPress sites fetch subresources over HTTP/2 on 96.9%, HTTP/3 on 77.0%, and HTTP/1.1 on 62.0%.
Across 65,509 WordPress sites, 96.9% fetch subresources over HTTP/2 (76% good LCP), 77.0% over HTTP/3, and 62.0% include at least one HTTP/1.1 request (74% good LCP).
Shopify 8,573 stores Shopify storefronts load subresources over HTTP/3 (98%), HTTP/2 (99.5%), and HTTP/1.1 (99.9%).
Across Shopify storefronts, 98.2% fetch subresources over HTTP/3, 99.5% over HTTP/2, and 99.9% include HTTP/1.1 subresource requests (97% good LCP overall).
React & Next.js 9,570 sites React sites reach 98.8% HTTP/2 and 90.7% HTTP/3 subresource adoption (79% good LCP).
Across 9,570 React sites, 98.8% serve subresources over HTTP/2 and 90.7% serve subresources over HTTP/3 (79% good LCP).
By Arjen Karel · 210,902 crawled sites (69,745 with desktop Chrome field data, 206,252 sites with subresource network protocols, October 2026). How we measured.