The State of Web Vitals

HTML compression

Compression on the HTML document: brotli, gzip, or none.

Field data PhoneDesktopAll Scope All sites Q1 2026 edition · Phone field outcomes
Metric LCP INP CLS
1

At a glance the headline numbers for HTML compression

Compression on the HTML document: brotli, gzip, or none.

7
Categories
94,906 sites
47.1%
Top share
gzip
0.00
Top CLS
Median for gzip

28.5% of HTML documents are Brotli-compressed. 19.4% ship raw.

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
2

HTML compression who uses what, and how stable each group is

Median CLS
0
0.05
0.10
0.15
0.20
0.25
gzip0.0047% of sites
br0.0029% of sites
none0.0019% of sites
zstd0.005% of sites
deflate0.000% of sites
VariantShare of sitesMedian
gzip 44,671 sites
47%
0.00
br 27,056 sites
29%
0.00
none 18,403 sites
19%
0.00
zstd 4,736 sites
5%
0.00
deflate 34 sites
0%
0.00

Little daylight between the groups: every variant sits near 0.00 median CLS. computed

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
3

Passing CLS per HTML compression which group passes the CLS most often

VariantSitesPassing CLSCLS
Br 28.5% 27,056 90% 0.00
Gzip 47.1% 44,671 89% 0.00
Deflate 0% 34 89% 0.00
None 19.4% 18,403 87% 0.00
Zstd 5% 4,736 85% 0.00
Good Needs Improvement Poor Sorted best-passing first · median colored by its own rating · pass = good CLS (0.1 at p75) · one value per site

90% of Br sites pass CLS. Zstd trails 5 points behind. computed

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
4

Why this matters for the Core Web Vitals, and where to start fixing it

The HTML document is the first thing the browser reads, and the sooner the markup arrives, the sooner the preload scanner can discover everything else: the stylesheets, the fonts, the LCP image. Brotli and gzip shrink HTML to a fraction of its raw size. None means the visitor downloads every byte of markup before the page can even start discovering resources.

Brotli compresses tighter than gzip and every major CDN offers it. This is a switch, not a project.

How does this affect the Core Web Vitals?

HTML compression correlates with the LCP. With Br, 86% of sites pass the LCP. With Zstd, 79% do.

Go fix it Configure Cloudflare for passing the Core Web Vitals → Compression mix →
Related signals HTTP protocol mix → Connection hints → Cache strategy mix → Uncompressed text responses → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured