Iframe loading attributes (default vs loading="lazy") and the Core Web Vitals
Default eager iframes (93.6%) versus loading="lazy" iframes (11.5%): how third-party embed scheduling affects Largest Contentful Paint across the 86,714 sites that use iframes.
93.6% of sites use default eager iframe loading, and 81% of those sites have a good LCP, against 82% of all sites.
11.5% of sites use loading="lazy" iframe loading, and 97% of those sites have a good INP, against 95% of all sites.
Core Web Vitals pass rate
Sites with default eager iframe loading have a good LCP most often: 81%, against 82% of all sites. Sites with loading="lazy" iframe loading have it least often, at 71%.
Sites with loading="lazy" iframe loading have a good INP most often: 97%, against 95% of all sites. Sites with default eager iframe loading have it least often, at 94%.
Iframe loading usage
Default eager is the most used: 93.6% of sites.
How iframe loading affects the four LCP phases
Across the four LCP sub-parts in Chrome's field data, the largest gap between default eager and loading="lazy" sits in time to first byte (TTFB): 641 ms median for default eager against 899 ms for loading="lazy". Overall median field LCP is 1.6s for default eager (TTFB 641 ms, load delay 369 ms, load duration 148 ms, render delay 238 ms) versus 1.8s for loading="lazy".
Across the four LCP sub-parts in Chrome's field data, the largest gap between default eager and loading="lazy" sits in time to first byte (TTFB): 641 ms median for default eager against 899 ms for loading="lazy". Overall median field LCP is 1.6s for default eager (TTFB 641 ms, load delay 369 ms, load duration 148 ms, render delay 238 ms) versus 1.8s for loading="lazy".
Understanding iframe loading
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, 93.6% include default eager iframes (81% good LCP, 1.6s median LCP) - often lightweight analytics or payment sandboxes - while 11.5% use loading="lazy" (71% good LCP, 1.9s median LCP), predominantly on article pages embedding heavy video players or maps.
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, 93.6% ship default eager iframes (81% good LCP) and 11.5% ship loading="lazy" iframes (71% 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.
How iframe loading plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 30,414 sites 19.3% of iframe-using WordPress sites lazy-load iframes, while 89.4% use default iframe loading.
WordPress 5.7+ adds loading="lazy" to iframes with wp_iframe_tag_add_loading_attr(). Across iframe-using WordPress sites, 19.3% use loading="lazy" (63% good LCP) and 89.4% use default iframe loading (67% good LCP).
Shopify 6,746 stores 98.9% of iframe-using Shopify stores load default iframes (95% good LCP).
Across iframe-using Shopify storefronts, 98.9% load default iframes (95% good LCP) and 3.9% use loading="lazy".
React & Next.js 5,283 sites Iframe-using React sites with lazy iframes (5.8%) pass LCP at 68% vs 84% with default iframes (16 points apart).
Across React sites that render iframes, 97.2% include default iframes (84% good LCP) and 5.8% include iframes with loading="lazy" (68% good LCP).
Wix 3,352 sites 99.6% of iframe-using Wix sites use default iframe loading (93% good LCP).
Across the 3,352 Wix sites that embed iframes, 99.6% use default iframe loading (93% good LCP) and 1.1% set loading="lazy".
By Arjen Karel · 210,902 crawled sites (196,263 with all devices Chrome field data, 86,714 sites with iframe loading, October 2026). How we measured.