The State of Web Vitals

Iframe loading attributes on React sites

Default eager iframes (97.2%) versus loading="lazy" iframes (5.8%): how third-party embed scheduling affects Largest Contentful Paint across the 5,283 sites that use iframes.

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

97.2% of React sites use default eager iframe loading, and 76% of those sites have a good LCP, against 79% of all React sites.

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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Core Web Vitals pass rate

Sites with default eager iframe loading have a good LCP most often: 76%, against 79% of all React sites.

SitesGood, needs improvement, poor LCPMedian
All React sites1,97979%1.5s
Default eager iframe (no loading="lazy") 97.2%1,15276%1.6s
Lazy-loaded iframe (loading="lazy") 5.8%6763%1.7s
GoodNeeds improvementPoorSites: with Chrome field data
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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Iframe loading usage

Default eager is the most used: 97.2% of React sites.

Sites using each option (sites can use more than one) 5,283 sites
Default eager iframe (no loading="lazy") 97.2%
Default eager iframe (no loading="lazy") 97.2% Lazy-loaded iframe (loading="lazy") 5.8%
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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How iframe loading affects the four LCP phases

Median LCP phase breakdown (Chrome field p75) Load delay Median LCP
React sites with iframe loading 813766 ms442 ms206 ms442 mslab 456 ms1.7s
Lazy-loaded iframe (loading="lazy") 47970 ms377 ms207 ms377 mslab 412 ms1.8s
Default eager iframe (no loading="lazy") 797755 ms446 ms206 ms446 mslab 458 ms1.7s
TTFB Resource load delay Resource load time Element render delay
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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Iframe loading per platform

Wix sets the iframe loading to default eager on 100% of its sites, and 92% of Wix sites have a good LCP, against 79% of all sites.

PlatformIframe loading on its sitesGood LCP
React sites with iframe loading 5,283 sitesDefault eager iframe (no loading="lazy") 97%79%
Wix 3,352 sitesDefault eager iframe (no loading="lazy") 100%92%
WordPress 1,198 sitesDefault eager iframe (no loading="lazy") 91%Lazy-loaded iframe (loading="lazy") 18%66%
Default eager iframe (no loading="lazy") Lazy-loaded iframe (loading="lazy")
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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Iframe loading or the platform

How embedded iframes compete for network and main-thread budget

Every eager iframe initializes a nested browsing context that fetches its own HTML, stylesheets, and scripts during page startup. Among iframe-using sites, 97.2% include default eager iframes (76% good LCP, 1.6s median LCP) - often lightweight analytics or payment sandboxes - while 5.8% use loading="lazy" (63% good LCP, 1.7s median LCP), predominantly on article pages embedding heavy video players or maps.

The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
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Understanding iframe loading

Add loading="lazy" to all visible below-the-fold video, map, and social iframes, or replace them with a click-to-load poster facade. Among sites with iframes, 97.2% ship default eager iframes (76% good LCP) and 5.8% ship loading="lazy" iframes (63% good LCP). Avoid putting loading="lazy" on hidden zero-pixel auth or analytics sandboxes, and never leave visible third-party media embeds eager during initial page load.

Go fix it Perfect YouTube Core Web Vitals → Google Maps with 100 percent PageSpeed → Speed up a Calendly integration →
The State of Web Vitals · October 2026 · React: 9,570 crawled sites · 1,979 with desktop field data · 5,283 sites with iframe loadingBy Arjen Karel · corewebvitals.io/state-of-cwv
Related signals Image format mix → Fonts per page → Font source → Script loading mix → By Arjen Karel · 9,570 crawled React sites (1,979 with desktop Chrome field data, 5,283 sites with iframe loading, October 2026) · How we measured