The State of Web Vitals

HTML size (kB)

The transfer size of the HTML document.

Field data PhoneDesktopAll Scope All sites Q2 2026 edition · Phone field outcomes
Metric LCP INP CLS
1

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

The transfer size of the HTML document.

21 KB
on the typical site
half of sites sit at or below
41 KB
1 in 4 sites exceed this
the top quarter
269 KB
the heaviest 1%
the long tail
185,262
sites measured
phone field data

The typical HTML document weighs 21 KB.

The State of Web Vitals · Q2 2026 · 189,915 sites · phone 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 26209 52418
0 0.1–0.215 0.215–0.46 0.46–0.988 0.988–2.12 2.12–4.55 4.55–9.76 9.76–20.9 20.9–44.9 44.9–96.4 96.4–207 >p98
Good (≤0.1) Needs improvement Poor (>0.25) Site count
The State of Web Vitals · Q2 2026 · 189,915 sites · phone 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 8,818 86% 0.00
0.1–0.215 310 91% 0.00
0.215–0.46 560 86% 0.00
0.46–0.988 1,845 80% 0.00
0.988–2.12 4,354 75% 0.00
2.12–4.55 8,226 87% 0.00
4.55–9.76 23,208 92% 0.00
9.76–20.9 44,740 91% 0.00
20.9–44.9 52,418 89% 0.00
44.9–96.4 25,858 87% 0.00
96.4–207 11,395 90% 0.00
>p98 3,530 87% 0.00
Good Needs Improvement Poor Faded rows: under 100 sites

HTML size (kB) 21 KB. p75 41 KB. p99 269 KB. At the low end (0 KB): CLS 0.00. At the high end (>p98): CLS 0.00. computed

The State of Web Vitals · Q2 2026 · 189,915 sites · phone 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, 83% of sites pass the LCP. Where it is high, 72% 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 189,915 sites, representing millions of real page loads · How we measured