v141 · performance
Speculation rules: desktop "eager" eagerness improvements
On desktop, "eager" eagerness speculation rules prefetches and prerenders now trigger when users hover on a link for a shorter time than the "moderate" mouse hover time. The previous behavior, of starting prefetch/prerenders as soon as possible, was the same as "immediate" eagerness. This new behavior is more useful as it better reflects the author's inte
concepts
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Desktop Eager Tuning
Speculation rules' eager eagerness tunes its trigger threshold up on desktop, lifting prerender hit rate for sites where bandwidth is cheap.
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Viewport Eager
Simulation of the four eagernesses across a scrollable list of 20 links. Watch which prefetches fire as you scroll, hover, or leave the page idle.
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Quicklink Replacement
The Quicklink library implements this exact heuristic in JS. Compare bundle cost, migration code, and the cooperative-fallback pattern.
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Rules Configurator
Build a
<script type="speculationrules">block interactively — pick eagerness (immediate / eager / moderate / conservative), set URL patterns, toggle prefetch vs prerender. The live JSON updates as you click; a hover-trigger simulator shows when each rule fires on desktop.
why it shipped
On desktop, "eager" eagerness speculation rules prefetches and prerenders now trigger when users hover on a link for a shorter time than the "moderate" mouse hover time. The previous behavior, of starting prefetch/prerenders as soon as possible, was the same as "immediate" eagerness. This new behavior is more useful as it better reflects the author's inte