demo · v143

Eagerness comparator

The four eagerness modes side-by-side: immediate, eager, moderate, conservative. v143 brings "eager" on mobile in line with desktop — short viewport dwell now triggers prerender, instead of waiting for explicit interaction. This page demos all four with live link probes, an interaction log, and a description of which mobile trigger each mode actually waits for.

Pick a strategy

Per-mode contract

immediate

aggressive
  • Trigger: as soon as the document parses.
  • Fetches every matching URL eagerly.
  • Use for: tiny known set of likely destinations.
Highest hit rate. Heaviest cost.

eager (v143 mobile-tuned)

aligned with desktop
  • Pre-v143 mobile: viewport dwell did NOT trigger; only pointerdown counted, costing prerender opportunities.
  • v143 mobile: anchor in viewport for a short dwell now triggers prerender, matching desktop "eager".
  • Use for: most "high confidence" link sets.
v143's fix — desktop and mobile finally agree.

moderate

balanced
  • Trigger: hover ~200ms OR pointerdown.
  • Stops at memory pressure / network type.
The default. Use this when you're not sure.

conservative

safe
  • Trigger: pointerdown only.
  • Almost never wastes bandwidth.
Use on Save-Data clients.

Interaction log

Hover and click the link badges above. The log records which trigger each link's eagerness would have used.

Snippet

<script type="speculationrules">
{
  "prerender": [
    { "where": { "href_matches": "/articles/*" }, "eagerness": "eager" }
  ]
}
</script>

// v143 mobile: "eager" no longer fires on viewport entry alone.
// Use "immediate" only when you really mean it.

see also