HTML compression (Brotli, Gzip, Zstandard) and the Core Web Vitals
Brotli (br), Gzip, Zstandard (zstd), or uncompressed HTML: how document compression affects Time to First Byte (561 ms on Brotli vs 707 ms on Gzip) and Largest Contentful Paint.
One in five sites, 20.8%, have no HTML compression. Of the 79.2% that do, 36% use Brotli, and 86% of those sites have a good LCP, against 82% of all sites.
LCP pass rate
Sites with Brotli HTML compression have a good LCP most often: 86%, against 82% of all sites. Sites with Zstandard HTML compression have it least often, at 78%.
HTML compression usage
Four in five sites uses HTML compression, and three in five of those use Gzip. Brotli is 36% of the sites with HTML compression, 28.1% of all sites.
Where HTML compression shows up in the four LCP phases
Across the four LCP sub-parts in Chrome's field data, the largest gap between Brotli and no sits in time to first byte (TTFB): 561 ms median for Brotli against 646 ms for no. Overall median field LCP is 1.5s for Brotli (TTFB 561 ms, load delay 399 ms, load duration 166 ms, render delay 238 ms) versus 1.6s for no.
Understanding HTML document compression
Why Brotli HTML compression speeds up resource discovery
Brotli uses a built-in dictionary of common HTML, CSS, and JavaScript tokens, shrinking HTML documents 15 to 20 percent more than Gzip at comparable CPU cost. Because the browser's preload scanner parses the HTML stream chunk by chunk as it arrives, a smaller compressed document delivers the <head> and hero <img> markup in fewer TCP or QUIC packets. Sites serving Brotli HTML record a 561 ms median TTFB and 1.5s median LCP, compared with 707 ms TTFB and 1.6s LCP on Gzip.
Enable Brotli (br) compression on your HTML responses and keep Gzip as a fallback. Across all audited sites, 28.1% serve Brotli-compressed HTML and reach 86% good LCP (1.5s median), beating Gzip (46.0% of sites, 81% good LCP) and uncompressed HTML (20.8% of sites, 80% good LCP). For dynamic HTML generated on the fly, Brotli quality level 4 or 5 compresses faster AND smaller than Gzip level 6 without adding server CPU delay.
How HTML compression plays out per platform
What the field data shows when you isolate a single CMS or framework.
WordPress 65,509 sites 50.2% of WordPress sites compress HTML with gzip (66% good LCP vs 78% with Brotli, 12 points apart).
Across WordPress sites, 50.2% serve gzip-compressed HTML (66% good LCP, 2.0s median), 31.4% serve Brotli-compressed HTML (78% good LCP, 1.8s median), and 12.3% send uncompressed HTML (64% good LCP).
React & Next.js 9,570 sites React & Next.js sites on Brotli (70.7%) pass LCP 24 percentage points more often than sites on gzip (17.9%).
Across React sites, 70.7% serve Brotli-compressed HTML (91% good LCP, 1.2s median) compared with 17.9% serving gzip-compressed HTML (67% good LCP, 2.0s median).
By Arjen Karel · 210,902 crawled sites (126,761 with phone Chrome field data, 206,145 sites with HTML compression, October 2026). How we measured.