WordPress HTTP cache TTL tiers and the Core Web Vitals

Sites with unspecified cache HTTP cache TTL tiers have a good LCP most often: 69%, against 70% of all WordPress sites. Sites with no-cache cache tiers have it least often, at 66%.

Unspecified cache is the most used: 99.0% of WordPress sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between unspecified cache and no-cache sits in time to first byte (TTFB): 1118 ms median for unspecified cache against 1159 ms for no-cache. Overall median field LCP is 2.0s for unspecified cache (TTFB 1118 ms, load delay 356 ms, load duration 181 ms, render delay 242 ms) versus 2.1s for no-cache.

Vue sets the HTTP cache TTL tiers to unspecified cache on 100% of its sites, and 67% of Vue sites have a good LCP, against 70% of all sites.

FrameworkHTTP cache TTL tiers on its sitesGood LCP

All WordPress sites 63,295 sitesUnspecified cache lifetime 99%Long TTL (> 30 days) 80%Medium TTL (1 - 30 days) 77%Short TTL (< 1 day) 72%Cache-Control: no-store 69%Cache-Control: no-cache 36%Cache-Control: immutable 16%70%

Alpine 380 sitesUnspecified cache lifetime 99%Long TTL (> 30 days) 91%Short TTL (< 1 day) 90%Medium TTL (1 - 30 days) 86%Cache-Control: no-store 84%Cache-Control: no-cache 49%Cache-Control: immutable 31%78%

jQuery 60,314 sitesUnspecified cache lifetime 99%Long TTL (> 30 days) 81%Medium TTL (1 - 30 days) 78%Short TTL (< 1 day) 73%Cache-Control: no-store 70%Cache-Control: no-cache 36%Cache-Control: immutable 16%69%

Vue 4,844 sitesUnspecified cache lifetime 100%Medium TTL (1 - 30 days) 67%Long TTL (> 30 days) 64%Cache-Control: no-store 54%Short TTL (< 1 day) 52%Cache-Control: no-cache 29%Cache-Control: immutable 14%67%

React 2,233 sitesUnspecified cache lifetime 100%Long TTL (> 30 days) 84%Medium TTL (1 - 30 days) 83%Short TTL (< 1 day) 77%Cache-Control: no-store 75%Cache-Control: no-cache 44%Cache-Control: immutable 19%63%

Unspecified cache lifetime Long TTL (> 30 days) Medium TTL (1 - 30 days) Short TTL (< 1 day) Cache-Control: no-store Cache-Control: no-cache Cache-Control: immutable

Does the framework explain the HTTP cache TTL tiers difference?

Almost every site with unspecified cache HTTP cache TTL tiers is a jQuery site, and almost every jQuery site has unspecified cache HTTP cache TTL tiers, so the data can't tell unspecified cache HTTP cache TTL tiers and jQuery apart. On Vue, 67% of sites with unspecified cache HTTP cache TTL tiers have a good LCP, against 69% of Vue sites with long-TTL. Within Vue, sites with unspecified cache and long-TTL have a good LCP about equally often. On React, 63% of sites with unspecified cache HTTP cache TTL tiers have a good LCP, against 61% of React sites with long-TTL. Within React, sites with unspecified cache and long-TTL have a good LCP about equally often.

How Cache-Control: immutable and long TTLs accelerate repeat views

Field Core Web Vitals combine first visits and repeat navigations from Chrome users. Sites that serve content-hashed static bundles with Cache-Control: immutable (15.8% of sites) achieve 67% good field LCP (2.0s median LCP), outperforming sites limited to short TTLs (71.6%, 67% good LCP) or no-store responses (68.9%, 67% good LCP).