Cacheable resource share on React sites

Sites with 50% to 79% cacheable resources cacheable resource share have a good LCP most often: 88%, against 85% of all React sites. Sites with under 20% cacheable resources cacheable share have it least often, at 62%.

80%+ cacheable resources is the most used: 58.3% of React sites. 50% to 79% cacheable resources is 28.8% of React sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between 50% to 79% cacheable resources and under 20% cacheable resources sits in time to first byte (TTFB): 496 ms median for 50% to 79% cacheable resources against 1185 ms for under 20% cacheable resources. Overall median field LCP is 1.4s for 50% to 79% cacheable resources (TTFB 496 ms, load delay 437 ms, load duration 137 ms, render delay 175 ms) versus 2.2s for under 20% cacheable resources.

On Wix, 68% of sites use 80%+ cacheable resources cacheable resource share, and 94% of Wix sites have a good LCP, against 85% of all sites. On WordPress, 46% of sites use 80%+ cacheable resources, and 61% of WordPress sites have a good LCP.

PlatformCacheable resource share on its sitesGood LCP

All React sites 9,570 sites80%+ cacheable resources 58%50% to 79% cacheable resources 29%85%

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%61%

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, 93% of sites with 50% to 79% cacheable resources cacheable resource share have a good LCP, against 95% of Wix sites with 80%+ cacheable resources. Within Wix, sites with 50% to 79% cacheable resources and 80%+ cacheable resources have a good LCP about equally often. On WordPress, 67% of sites with 50% to 79% cacheable resources cacheable resource share have a good LCP, against 61% of WordPress sites with 80%+ cacheable resources. Within WordPress, sites with 50% to 79% cacheable resources and 80%+ 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 88% pass field LCP (1.3s and 1.4s median). When cacheability falls to 20% to 49% (3.5%), good LCP drops to 70% (1.9s median), and below 20% cacheable (9.5%, 906 sites) good LCP drops to 62% (2.2s median).