The State of Web Vitals

HTML size (kB)

The transfer size of the HTML document.

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

At a glance the headline numbers for HTML size (kB)

The transfer size of the HTML document.

22 KB
on the typical site
half of sites sit at or below
42 KB
1 in 4 sites exceed this
the top quarter
273 KB
the heaviest 1%
the long tail
94,906
sites measured
all-device field data

The typical HTML document weighs 22 KB.

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

Distribution & median CLS site count and median CLS at each level of HTML size (kB)

0.00 0.04 0.08 0.11 0.15
0.1
0 13674 27347
0 0.1–0.215 0.215–0.461 0.461–0.989 0.989–2.12 2.12–4.56 4.56–9.79 9.79–21 21–45.1 45.1–96.8 96.8–208 >p98
Good (≤0.1) Needs improvement Poor (>0.25) Site count
The State of Web Vitals · Q1 2026 · 94,910 sites · all devices field datacorewebvitals.io/state-of-cwv
3

Passing CLS by HTML size (kB) which level passes the CLS most often

HTML size (kB)SitesPassing CLSCLS
0 2,447 84% 0.01
0.1–0.215 154 94% 0.00
0.215–0.461 291 84% 0.00
0.461–0.989 945 80% 0.00
0.989–2.12 2,295 76% 0.01
2.12–4.56 4,288 87% 0.00
4.56–9.79 11,912 91% 0.00
9.79–21 23,989 90% 0.00
21–45.1 27,347 88% 0.00
45.1–96.8 13,495 85% 0.01
96.8–208 5,893 89% 0.00
>p98 1,850 86% 0.00
Good Needs Improvement Poor Faded rows: under 100 sites

HTML size (kB) 22 KB. p75 42 KB. p99 273 KB. At the low end (0 KB): CLS 0.01. At the high end (>p98): CLS 0.00. computed

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

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

HTML size is parse-and-discover time. The browser reads the document from the top, and everything it should find early (the stylesheets, the LCP image) sits deeper in a big document. Very large HTML usually means inlined payloads: base64 images, server-rendered JSON state, giant inline scripts.

The early bytes matter most. The first network round trip delivers only the start of the document, so what sits in the head decides what the browser can do while the rest streams in. Keep the head lean and put the critical references early.

How does HTML size affect the Core Web Vitals?

HTML size correlates with the LCP. Where the HTML size is low, 84% of sites pass the LCP. Where it is high, 73% do. The decline is gradual. There is no point where sites suddenly start failing.

Go fix it Preload the LCP image → Eliminate render-blocking resources → 103 Early Hints →
Related signals HTTP protocol mix → HTTP protocol → ETag present → Cache strategy mix → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured