The State of Web Vitals

Subresource network protocols on React sites

HTTP/2 (98.8%), HTTP/3 QUIC (90.7%), and legacy HTTP/1.1 (90.4%) across all page subrequests: how connection protocols move Largest Contentful Paint.

Field data PhoneDesktopAll Scope All sites October 2026 edition · All devices field outcomes · React sites only
React Scoped to 9,570 sites out of 210,902 analyzed (frameworks) Compare with all sites →

90.4% of React sites use HTTP/1.1 subresource network protocols, and 86% of those sites have a good LCP, against 85% of all React sites.

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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LCP pass rate

Sites with HTTP/1.1 subresource network protocols have a good LCP most often: 86%, against 85% of all React sites. Sites with HTTP/2 network protocols have it least often, at 85%.

SitesGood, needs improvement, poor LCPMedian
All React sites9,11085%1.4s
HTTP/1.1 90.4%8,24886%1.4s
HTTP/3 (QUIC / h3) 90.7%8,26385%1.4s
HTTP/2 (h2) 98.8%8,99785%1.4s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Subresource network protocols usage

HTTP/2 is the most used: 98.8% of React sites. HTTP/1.1 is 90.4% of React sites.

Sites using each option (sites can use more than one) 9,570 sites
HTTP/2 (h2) 98.8% HTTP/3 (QUIC / h3) 90.7% HTTP/1.1 90.4%
HTTP/2 (h2) 98.8% HTTP/3 (QUIC / h3) 90.7% HTTP/1.1 90.4%
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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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/1.1 and HTTP/2 sits in time to first byte (TTFB): 485 ms median for HTTP/1.1 against 515 ms for HTTP/2. Overall median field LCP is 1.4s for HTTP/1.1 (TTFB 485 ms, load delay 446 ms, load duration 145 ms, render delay 170 ms) versus 1.4s for HTTP/2.

Median LCP phase breakdown (Chrome field p75) Load delay Median LCP
All React sites 6,740516 ms439 ms146 ms175 ms439 mslab 439 ms1.4s
HTTP/2 (h2) 6,671515 ms440 ms146 ms174 ms440 mslab 440 ms1.4s
HTTP/1.1 6,131485 ms446 ms145 ms170 ms446 mslab 446 ms1.4s
HTTP/3 (QUIC / h3) 6,121499 ms447 ms145 ms172 ms447 mslab 447 ms1.4s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Subresource network protocols per platform

Wix sets the subresource network protocols to HTTP/1.1 on 100% of its sites, and 94% of Wix sites have a good LCP, against 85% of all sites. WordPress sets the subresource network protocols to HTTP/2 on 97% of its sites, and 61% of WordPress sites have a good LCP.

PlatformSubresource network protocols on its sitesGood LCP
All React sites 9,570 sitesHTTP/2 (h2) 99%HTTP/3 (QUIC / h3) 91%HTTP/1.1 90%85%
Wix 5,824 sitesHTTP/2 (h2) 100%HTTP/1.1 100%HTTP/3 (QUIC / h3) 99%94%
WordPress 2,342 sitesHTTP/2 (h2) 97%HTTP/3 (QUIC / h3) 80%HTTP/1.1 70%61%
HTTP/2 (h2) HTTP/3 (QUIC / h3) HTTP/1.1
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Subresource network protocols or the platform

Does the platform explain the subresource network protocols difference?

On Wix, 94% of sites with HTTP/1.1 subresource network protocols have a good LCP, against 94% of Wix sites with HTTP/2. Within Wix, sites with HTTP/1.1 and HTTP/2 have a good LCP about equally often. On WordPress, 56% of sites with HTTP/1.1 subresource network protocols have a good LCP, against 60% of WordPress sites with HTTP/2. Within WordPress, sites with HTTP/1.1 and HTTP/2 have a good LCP about equally often.

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, 98.8% load subresources over HTTP/2 (85% good LCP), 90.7% negotiate HTTP/3 on at least one origin (85% good LCP), and 90.4% still make at least one legacy HTTP/1.1 request (86% good LCP).

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
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Understanding subresource network protocols

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 (90.4% 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.

Go fix it Third-party domains → Configure Cloudflare for passing the Core Web Vitals →
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 9,110 with all devices field dataBy Arjen Karel · corewebvitals.io/state-of-cwv
Related signals Connection hints → Main CDN → HTTP protocol → HTML compression → By Arjen Karel · 9,570 crawled React sites (9,110 with all devices Chrome field data, October 2026) · How we measured