Cacheable resource share on React sites

Sites with 80%+ cacheable resources cacheable resource share have a good LCP most often: 88%, against 84% of all React sites. Sites with under 20% cacheable resources cacheable share have it least often, at 64%.

80%+ cacheable resources is the most used: 58.3% of React sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between 80%+ cacheable resources and under 20% cacheable resources sits in time to first byte (TTFB): 453 ms median for 80%+ cacheable resources against 1110 ms for under 20% cacheable resources. Overall median field LCP is 1.3s for 80%+ cacheable resources (TTFB 453 ms, load delay 439 ms, load duration 127 ms, render delay 168 ms) versus 2.2s for under 20% cacheable resources.

Wix sets the cacheable resource share to 80%+ cacheable resources on 68% of its sites, and 94% of Wix sites have a good LCP, against 84% of all sites.

PlatformCacheable resource share on its sitesGood LCP

All React sites 9,570 sites80%+ cacheable resources 58%50% to 79% cacheable resources 29%84%

Wix 5,824 sites80%+ cacheable resources 68%50% to 79% cacheable resources 31%94%

WordPress 2,342 sites80%+ cacheable resources 46%Under 20% cacheable resources 31%50% to 79% cacheable resources 16%63%

80%+ cacheable resources 50% to 79% cacheable resources Under 20% cacheable resources 20% to 49% cacheable resources

Does the platform explain the cacheable resource share difference?

On Wix, 95% of sites with 80%+ cacheable resources cacheable resource share have a good LCP, against 93% of Wix sites with 50% to 79% cacheable resources. Within Wix, sites with 80%+ cacheable resources and 50% to 79% cacheable resources have a good LCP about equally often. On WordPress, 64% of sites with 80%+ cacheable resources cacheable resource share have a good LCP, against 68% of WordPress sites with 50% to 79% cacheable resources. Within WordPress, sites with 80%+ cacheable resources and 50% to 79% cacheable resources have a good LCP about equally often.

How subresource Cache-Control coverage speeds up repeat visits and CDN edge hits

Cacheable resource share tracks the percentage of page requests carrying valid Cache-Control or Expires headers. Across 5,575 sites (58.3%) with 80%+ cacheable resources and 2,756 sites (28.8%) at 50% to 79%, 88% and 86% pass field LCP (1.3s and 1.4s median). When cacheability falls to 20% to 49% (3.5%), good LCP drops to 69% (2.0s median), and below 20% cacheable (9.5%, 906 sites) good LCP drops to 64% (2.2s median).