The State of Web Vitals

HTTP protocol

The HTTP protocol of the HTML document response.

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

At a glance the headline numbers for HTTP protocol

The HTTP protocol of the HTML document response.

3
Categories
94,906 sites
63.1%
Top share
h2
0.00
Top CLS
Median for h2

23.9% of HTML documents arrive over HTTP/3.

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

HTTP protocol who uses what, and how stable each group is

Median CLS
0
0.05
0.10
0.15
0.20
0.25
h20.0063% of sites
h30.0024% of sites
http/1.10.0013% of sites
VariantShare of sitesMedian
h2 59,859 sites
63%
0.00
h3 22,679 sites
24%
0.00
http/1.1 12,368 sites
13%
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 HTTP protocol which group passes the CLS most often

VariantSitesPassing CLSCLS
H3 23.9% 22,679 90% 0.00
H2 63.1% 59,859 89% 0.00
Http/1.1 13% 12,368 87% 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

No variant stands out: pass rates sit between 87% and 90%. 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 protocol decides how expensive a connection is. HTTP/3 sets up in fewer round trips and a lost packet no longer stalls everything behind it, which TCP-based protocols suffer from. The document request is where this matters most: it is the first request of the visit and it carries the whole TTFB.

There is a catch on the very first visit. Browsers often discover HTTP/3 support through a header on a previous response (Alt-Svc), so the first document fetch can still pay the older protocol's price. DNS HTTPS records fix that discovery, and your CDN controls whether they exist.

How does this affect the Core Web Vitals?

HTTP protocol correlates with the LCP. With H3, 86% of sites pass the LCP. With H2, 80% do.

Go fix it TTFB: connection duration → Configure Cloudflare for passing the Core Web Vitals →
Related signals Uncompressed text responses → HTML size (kB) → Connection hints → ETag present → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured