Synthetic paint milestones and the Core Web Vitals
28.7% of audited sites (58,558) paint their hero element in under 300ms in the lab and pass field LCP at 93% (1.1s median), while the 22.2% exceeding 1,500ms in the lab pass field LCP at just 62% (2.1s median).
28.7% of sites use under 300ms lab LCP synthetic paint milestones, and 93% of those sites have a good LCP, against 82% of all sites.
LCP pass rate
Sites with under 300ms lab LCP synthetic paint milestones have a good LCP most often: 93%, against 82% of all sites. Sites with over 1,500ms lab LCP lab paint time have it least often, at 62%.
Synthetic paint milestones usage
Under 300ms lab LCP is the most used: 28.7% of sites.
The four LCP phases
Across the four LCP sub-parts in Chrome's field data, the largest gap between under 300ms lab LCP and over 1,500ms lab LCP sits in time to first byte (TTFB): 451 ms median for under 300ms lab LCP against 1043 ms for over 1,500ms lab LCP. Overall median field LCP is 1.1s for under 300ms lab LCP (TTFB 451 ms, load delay 244 ms, load duration 127 ms, render delay 205 ms) versus 2.1s for over 1,500ms lab LCP.
Understanding synthetic paint milestones
How clean lab paint timings translate to real-user field LCP
Synthetic paint milestones measure your page without real-user cellular latency or cold device caches. A page that already takes over 1.5 seconds in a fast lab environment rarely survives real-world mobile networks. Across 58,558 sites (28.7%) painting under 300ms in the lab, 93% pass field LCP (1.1s median), dropping to 62% (2.1s median) on the 22.2% (45,370) over 1,500ms.
Optimize unthrottled server TTFB and eliminate render-blocking head resources so the baseline paint path finishes in under 600ms in clean lab conditions. Across all audited sites, 28.7% finish lab LCP under 300ms (93% good LCP, 1.1s median) versus 22.2% above 1,500ms (62% good LCP, 2.1s median).
How synthetic paint milestones plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,356 sites WordPress sites over 1,500ms lab LCP pass field LCP at 48% vs 89% under 300ms.
Across WordPress sites, 32% take over 1,500ms to paint in unthrottled lab conditions (48% field LCP pass rate, 2.6s median) compared with 89% (1.3s median) on the 16% painting under 300ms.
Shopify 8,564 sites 68% of Shopify stores paint between 300ms and 1,500ms in the lab.
Across Shopify storefronts, 38% record a 600 to 1,500ms lab LCP (95% field LCP pass rate, 1.4s median) and 30% paint in 300 to 600ms (98%, 1.2s median).
React 9,561 sites React sites painting under 300ms in the lab pass field LCP 25 points more often than sites over 1,500ms.
Across React sites, 46% paint their hero element in under 300ms in the lab (95% field LCP pass rate, 1.1s median) compared with 26% taking over 1,500ms (70% pass rate, 1.8s median).
Wix 5,824 sites 63% of Wix sites complete lab LCP in under 300ms.
Across Wix sites, 63% paint in under 300ms in the lab (96% field LCP pass rate, 1.1s median) compared with 91% on the 21% exceeding 1,500ms.
By Arjen Karel · 210,902 crawled sites (196,263 with all devices Chrome field data, 204,313 sites with synthetic paint milestones, October 2026). How we measured.