The State of Web Vitals

Speculation posture

The strongest speculation rule the document declares: none, prefetch, prerender-until-script, prerender.

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

At a glance the headline numbers for Speculation posture

The strongest speculation rule the document declares: none, prefetch, prerender-until-script, prerender.

4
Categories
185,226 sites
65.7%
Top share
none
0.00
Top CLS
Median for none

65.7% of sites declare no speculation rules at all.

The State of Web Vitals · Q2 2026 · 189,915 sites · phone field datacorewebvitals.io/state-of-cwv
2

Speculation posture who uses what, and how stable each group is

Median CLS
0
0.05
0.10
0.15
0.20
0.25
none0.0066% of sites
prefetch0.0034% of sites
prerender0.001% of sites
prerender_until_script0.000% of sites
VariantShare of sitesMedian
none 121,738 sites
66%
0.00
prefetch 62,089 sites
34%
0.00
prerender 908 sites
1%
0.00
prerender_until_script 491 sites
0%
0.00

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

The State of Web Vitals · Q2 2026 · 189,915 sites · phone field datacorewebvitals.io/state-of-cwv
3

Passing CLS per speculation posture which group passes the CLS most often

VariantSitesPassing CLSCLS
Prerender until script 0.3% 491 96% 0.00
Prefetch 33.5% 62,089 91% 0.00
None 65.7% 121,738 88% 0.00
Prerender 0.5% 908 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

96% of Prerender until script sites pass CLS. Prerender trails 9 points behind. 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

Speculation rules let the browser start the next navigation before the click. Prefetch downloads the next document ahead of time. Prerender goes further and builds the whole next page in a hidden renderer, so navigating to it is a swap instead of a load. Prerender-until-script is the cautious middle: build the page, hold the scripts.

Done right, the next page's LCP is near-instant because it painted before the visitor arrived. The cost is speculative work: prerendering pages nobody visits burns server and client resources. That trade is what eagerness controls.

How does this affect the Core Web Vitals?

Speculation posture correlates with the CLS. With Prerender until script, 96% of sites pass the CLS. With Prerender, 87% do. The causal link is weak: the choice mostly marks what kind of site made it.

The split is bigger on LCP. With Prerender until script, 93% of sites pass it. With Prefetch, 72% do.

Go fix it Speculation rules → The prerender-until-script speculation rule → View transitions and web performance →
Related signals Speculation eagerness → Chrome field data from 189,915 sites, representing millions of real page loads · How we measured