LCP sub-part breakdown and the Core Web Vitals
TTFB is the largest LCP sub-part on 69.2% of audited sites (98,468, 86% good LCP), followed by resource load delay on 20.6% (86% good LCP) and element render delay on 8.1% (90% good LCP).
2.0% of sites use resource load duration as the largest LCP sub-part LCP sub-part breakdown, and 95% of those sites have a good LCP, against 86% of all sites.
LCP pass rate
Sites with resource load duration as the largest LCP sub-part LCP sub-part breakdown have a good LCP most often: 95%, against 86% of all sites. Sites with TTFB as the largest LCP sub-part dominant LCP phase have it least often, at 86%.
LCP sub-part breakdown usage
TTFB as the largest LCP sub-part is the most used: 69.2% of sites. Resource load duration as the largest LCP sub-part is 2.0% of sites.
The four LCP phases
Across the four LCP sub-parts in Chrome's field data, the largest gap between resource load duration as the largest LCP sub-part and TTFB as the largest LCP sub-part sits in time to first byte (TTFB): 282 ms median for resource load duration as the largest LCP sub-part against 778 ms for TTFB as the largest LCP sub-part. Overall median field LCP is 1.2s for resource load duration as the largest LCP sub-part (TTFB 282 ms, load delay 217 ms, load duration 398 ms, render delay 172 ms) versus 1.4s for TTFB as the largest LCP sub-part.
Understanding LCP sub-part breakdown
Why network transfer duration is rarely the real LCP bottleneck
Resource load duration is the largest sub-part on just 2.0% (2,917) of audited sites. Most LCP failures happen while waiting for the first HTML byte (69.2% TTFB-dominated, 86% good LCP, 1.4s median), waiting to discover the hero image (20.6% load-delay-dominated, 86% good LCP), or waiting on blocking head scripts and stylesheets (8.1% render-delay-dominated, 90% good LCP).
Fix your largest LCP sub-part first: cache HTML at the CDN edge when TTFB dominates, preload the hero image when load delay dominates, or remove blocking head scripts when render delay dominates. Across all audited sites, 69.2% are TTFB-dominated (86% good LCP, 1.4s median) versus 20.6% load-delay-dominated (86% good LCP, 1.4s median).
How LCP sub-part breakdown plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 45,074 sites Server TTFB is the largest LCP phase on 84% of WordPress sites (74% good LCP vs 83% when load delay leads).
Across WordPress sites, TTFB is the largest LCP sub-part on 84% (74% LCP pass rate, 1.8s median) and load delay is the largest sub-part on 9% (83% pass rate, 1.5s median).
Shopify 7,269 sites Resource load delay is the largest LCP phase on 69% of Shopify stores (97% good LCP).
Across Shopify storefronts, resource load delay is the largest LCP sub-part on 69% of stores (97% LCP pass rate, 1.2s median) and render delay is the largest sub-part on 15% (94% pass rate, 1.5s median).
React 6,740 sites TTFB is the largest LCP sub-part on 56% of React sites (72% good LCP vs 88% when load delay leads, 16 points apart).
Across React sites, TTFB is the largest LCP sub-part on 56% (72% LCP pass rate, 1.8s median) and load delay is the largest sub-part on 39% (88% pass rate, 1.3s median).
By Arjen Karel · 210,902 crawled sites (69,745 with desktop Chrome field data, 142,347 sites with LCP sub-part breakdown, October 2026). How we measured.