WordPress uncompressed text responses and the Core Web Vitals

Sites with full text compression text compression coverage have a good LCP most often: 78%, against 76% of all WordPress sites. Sites with uncompressed text responses text compression have it least often, at 72%.

Full text compression is the most used: 67.1% of WordPress sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between full text compression and uncompressed text responses sits in time to first byte (TTFB): 960 ms median for full text compression against 1066 ms for uncompressed text responses. Overall median field LCP is 1.7s for full text compression (TTFB 960 ms, load delay 270 ms, load duration 131 ms, render delay 217 ms) versus 1.9s for uncompressed text responses.

jQuery sets the text compression coverage to full text compression on 67% of its sites, and 75% of jQuery sites have a good LCP, against 76% of all sites.

FrameworkText compression coverage on its sitesGood LCP

All WordPress sites 63,295 sitesAll text compressed 67%Has uncompressed text 33%76%

Alpine 380 sitesAll text compressed 55%Has uncompressed text 45%82%

jQuery 60,314 sitesAll text compressed 67%Has uncompressed text 33%75%

Vue 4,844 sitesAll text compressed 63%Has uncompressed text 37%75%

React 2,233 sitesAll text compressed 59%Has uncompressed text 41%66%

All text compressed Has uncompressed text

Does the framework explain the text compression coverage difference?

On jQuery, 78% of sites with full text compression text compression coverage have a good LCP, against 71% of jQuery sites with uncompressed text responses. Within jQuery, sites with full text compression have a good LCP more often. On Vue, 79% of sites with full text compression text compression coverage have a good LCP, against 68% of Vue sites with uncompressed text responses. Within Vue, sites with full text compression have a good LCP more often.

Where uncompressed text responses slip through on modern web stacks

Almost no server intentionally disables compression globally. Instead, uncompressed text responses slip through narrow MIME-type allowlists (forgetting image/svg+xml or application/json in nginx or Apache) or come from third-party API and widget endpoints that bypass the primary CDN. Across 42,465 sites (67.1%) that compress every text response, good LCP reaches 78% (1.7s median, 960 ms TTFB), whereas the 20,830 sites (32.9%) shipping at least one uncompressed text payload drop to 72% good LCP (1.9s median, 1066 ms TTFB).