v144 · performance · demo

Timing Dashboard

The performance payoff of prerendering, measured live. This page embeds a <script type="speculationrules"> block and records real navigation timing for TTFB, LCP, and total load time — with and without prerender active. The gap between the two bars is your prerender dividend.

The until action for prerender is behind a flag in Chrome 144. Enable chrome://flags/#enable-experimental-web-platform-features. Prerender itself (without until) ships fully in Chrome 109+. This demo uses standard prerender + prerenderingchange / document.prerendering APIs.
Speculation Rules API: checking… Prerender state: checking…
speculation rules injected into page
browser warming target URL
prerender ready (activate on navigate)

Navigation timing for this page load (performance.getEntriesByType('navigation')[0]):

Timing comparison: normal navigation vs prerendered navigation (ms, lower is better)

without prerender
with prerender
TTFB
—
LCP
—
load time
—
metric without prerender with prerender saving
TTFB — — —
LCP — — —
Load time — — —

Click "Use real timing" to read actual PerformanceNavigationTiming, or "Simulate" for a realistic comparison.

the API

<!-- Embed speculation rules to prerender a page immediately -->
<script type="speculationrules">
{
  "prerender": [{
    "urls": ["/checkout/confirm"],
    "eagerness": "immediate"
  }]
}
</script>

// Check if the current page is being prerendered
if (document.prerendering) {
  document.addEventListener('prerenderingchange', () => {
    // Page has been activated — record timing
    const nav = performance.getEntriesByType('navigation')[0];
    console.log('TTFB after activation:', nav.responseStart);
  });
}

// Read navigation timing to measure the prerender dividend
const nav = performance.getEntriesByType('navigation')[0];
const ttfb = nav.responseStart;
const loadTime = nav.loadEventEnd - nav.startTime;
// activationStart is set on prerendered pages; compare to 0 for normal pages
const activationStart = nav.activationStart ?? 0;

see also