WordPress subresource compression algorithms and the Core Web Vitals

Sites with unencoded binary assets subresource HTTP compression have a good LCP most often: 76%, against 76% of all WordPress sites. Sites with Zstandard (zstd) compression subresource compression have it least often, at 74%.

Unencoded binary assets is the most used: 99.9% of WordPress sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between unencoded binary assets and Zstandard (zstd) compression sits in time to first byte (TTFB): 999 ms median for unencoded binary assets against 1035 ms for Zstandard (zstd) compression. Overall median field LCP is 1.8s for unencoded binary assets (TTFB 999 ms, load delay 289 ms, load duration 129 ms, render delay 219 ms) versus 1.8s for Zstandard (zstd) compression.

Vue sets the subresource HTTP compression to unencoded binary assets on 100% of its sites, and 75% of Vue sites have a good LCP, against 76% of all sites.

FrameworkSubresource HTTP compression on its sitesGood LCP

All WordPress sites 63,295 sitesUnencoded binary assets (images / WOFF2) 100%Gzip (Content-Encoding: gzip) 91%Brotli (Content-Encoding: br) 72%Zstandard (Content-Encoding: zstd) 56%76%

Alpine 380 sitesUnencoded binary assets (images / WOFF2) 100%Gzip (Content-Encoding: gzip) 95%Brotli (Content-Encoding: br) 86%Zstandard (Content-Encoding: zstd) 79%82%

jQuery 60,314 sitesUnencoded binary assets (images / WOFF2) 100%Gzip (Content-Encoding: gzip) 92%Brotli (Content-Encoding: br) 72%Zstandard (Content-Encoding: zstd) 57%75%

Vue 4,844 sitesUnencoded binary assets (images / WOFF2) 100%Gzip (Content-Encoding: gzip) 84%Brotli (Content-Encoding: br) 65%Zstandard (Content-Encoding: zstd) 34%75%

React 2,233 sitesUnencoded binary assets (images / WOFF2) 100%Gzip (Content-Encoding: gzip) 93%Brotli (Content-Encoding: br) 80%Zstandard (Content-Encoding: zstd) 61%66%

Unencoded binary assets (images / WOFF2) Gzip (Content-Encoding: gzip) Brotli (Content-Encoding: br) Zstandard (Content-Encoding: zstd)

Does the framework explain the subresource HTTP compression difference?

Almost every site with unencoded binary assets subresource HTTP compression is a jQuery site, and almost every jQuery site has unencoded binary assets subresource HTTP compression, so the data can't tell unencoded binary assets subresource HTTP compression and jQuery apart. On Vue, 75% of sites with unencoded binary assets subresource HTTP compression have a good LCP, against 74% of Vue sites with Gzip compression. Within Vue, sites with unencoded binary assets and Gzip compression have a good LCP about equally often. On React, 66% of sites with unencoded binary assets subresource HTTP compression have a good LCP, against 65% of React sites with Gzip compression. Within React, sites with unencoded binary assets and Gzip compression have a good LCP about equally often.