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 Q1 2026 edition · All devices 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
94,890 sites
65.0%
Top share
none
0.00
Top CLS
Median for none

65.0% of sites declare no speculation rules at all.

The State of Web Vitals · Q1 2026 · 94,910 sites · all devices 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
none0.0065% of sites
prefetch0.0034% of sites
prerender_until_script0.000% of sites
prerender0.011% of sites
VariantShare of sitesMedian
none 61,678 sites
65%
0.00
prefetch 32,465 sites
34%
0.00
prerender_until_script 269 sites
0%
0.00
prerender 478 sites
1%
0.01

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

The State of Web Vitals · Q1 2026 · 94,910 sites · all devices 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% 269 99% 0.00
Prefetch 34.2% 32,465 90% 0.00
None 65% 61,678 87% 0.00
Prerender 0.5% 478 85% 0.01
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

99% of Prerender until script sites pass CLS. Prerender trails 14 points behind. 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

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 Prefetch, 90% of sites pass the CLS. With Prerender, 85% do. The causal link is weak: the choice mostly marks what kind of site made it.

The split is bigger on LCP. With None, 88% of sites pass it. With Prefetch, 73% 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 94,910 sites, representing millions of real page loads · How we measured