Subresource compression algorithms and the Core Web Vitals
87.6% of audited sites (180,762) serve Gzip-compressed subresources (81% good LCP), 66.8% serve Brotli (81% good LCP), 48.9% serve Zstandard (80% good LCP), and the 4.0% adopting Dictionary-Compressed Brotli (dcb) reach 95% good LCP (1.3s median).
4.0% of sites use Dictionary-Compressed Brotli (dcb) subresource HTTP compression, and 95% of those sites have a good LCP, against 82% of all sites.
LCP pass rate
Sites with Dictionary-Compressed Brotli (dcb) subresource HTTP compression have a good LCP most often: 95%, against 82% of all sites. Sites with Zstandard (zstd) compression subresource compression have it least often, at 80%.
Subresource HTTP compression usage
Unencoded binary assets is the most used: 99.6% of sites. Dictionary-Compressed Brotli (dcb) is 4.0% of sites.
LCP phase breakdown by subresource compression algorithm
Across the four LCP sub-parts in Chrome's field data, the largest gap between Dictionary-Compressed Brotli (dcb) and Zstandard (zstd) compression sits in time to first byte (TTFB): 400 ms median for Dictionary-Compressed Brotli (dcb) against 690 ms for Zstandard (zstd) compression. Overall median field LCP is 1.4s for Dictionary-Compressed Brotli (dcb) (TTFB 400 ms, load delay 586 ms, load duration 206 ms, render delay 312 ms) versus 1.7s for Zstandard (zstd) compression.
Understanding subresource compression algorithms
Brotli, Zstandard (zstd), and Dictionary-Compressed Brotli (dcb) across page subresources
Nearly every page (99.6%) transfers pre-compressed binary formats like WebP, AVIF, and WOFF2 without extra Content-Encoding. For text subresources (JS, CSS, SVG, JSON), 87.6% of sites use Gzip (81% good LCP, 1.6s median), 66.8% use Brotli (81% good LCP), 48.9% include Zstandard responses (80% good LCP, often from Meta/Google third-party scripts), and 4.0% (8,218 sites, led by Shopify/Cloudflare) use shared-dictionary Brotli (dcb) to achieve 95% good LCP (1.3s median).
Enable Brotli (br) and Zstandard (zstd) at your CDN edge for all text-based subresources (text/css, application/javascript, image/svg+xml, application/json) to shrink transfer size by 15% to 25% over Gzip. Across all audited sites, 66.8% serve Brotli subresources (81% good LCP) and 4.0% serve Dictionary-Compressed Brotli (95% good LCP).
How subresource HTTP compression plays out per platform
What the field data shows when you isolate a single CMS or framework.
Shopify 8,573 stores 95.5% of Shopify stores use Dictionary-Compressed Brotli (dcb) alongside Brotli (100.0%), passing LCP at 95%.
Across Shopify storefronts, 100.0% serve Brotli (br) responses (95% good LCP) and 95.5% serve Compression Dictionary Transport (dcb) responses (95% good LCP, 1.3s median).
React & Next.js 9,570 sites 91.1% of React & Next.js sites serve Brotli-compressed subresources (85% good LCP, 1.4s median).
Across 9,570 React sites, 91.1% serve Brotli-compressed bundles (85% good LCP), 97.7% use Gzip (84% good LCP), and 41.3% include Zstandard-compressed scripts (76% good LCP).
Wix 5,825 sites 100.0% of Wix sites serve Brotli and Gzip subresources (94% good LCP, 1.1s median).
Across 5,825 Wix sites, 100.0% serve Brotli-compressed subresources (94% good LCP, 1.1s median), 100.0% serve Gzip, and 31.6% include Zstandard-encoded responses (90% good LCP).
By Arjen Karel · 210,902 crawled sites (126,761 with phone Chrome field data, 206,252 sites with subresource HTTP compression, October 2026). How we measured.