Synthetic paint milestones on Wix sites

Sites with under 300ms lab LCP synthetic paint milestones have a good LCP most often: 95%, against 92% of all Wix sites. Sites with over 1,500ms lab LCP lab paint time have it least often, at 87%.

Under 300ms lab LCP is the most used: 62.8% of Wix sites.

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 resource load delay: 459 ms median for under 300ms lab LCP against 516 ms for over 1,500ms lab LCP. Overall median field LCP is 1.2s for under 300ms lab LCP (TTFB 314 ms, load delay 459 ms, load duration 258 ms, render delay 138 ms) versus 1.3s for over 1,500ms lab LCP.

React sets the synthetic paint milestones to under 300ms lab LCP on 63% of its sites, and 92% of React sites have a good LCP, against 92% of all sites.

FrameworkSynthetic paint milestones on its sitesGood LCP

Wix sites with synthetic paint milestones 5,620 sitesUnder 300ms lab LCP 63%Over 1,500ms lab LCP 21%300 to 600ms lab LCP 11%92%

React 5,619 sitesUnder 300ms lab LCP 63%Over 1,500ms lab LCP 21%300 to 600ms lab LCP 11%92%

Under 300ms lab LCP Over 1,500ms lab LCP 300 to 600ms lab LCP 600 to 1,500ms lab LCP

Does the framework explain the synthetic paint milestones difference?

On React, 95% of sites with under 300ms lab LCP synthetic paint milestones have a good LCP, against 87% of React sites with over 1,500ms lab LCP. Within React, sites with under 300ms lab LCP have a good LCP more often.

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 3,532 sites (62.8%) painting under 300ms in the lab, 95% pass field LCP (1.1s median), dropping to 87% (1.3s median) on the 20.8% (1,171) over 1,500ms.