Speculation Rules API in 2026: near-instant nav, zero JS

From the archive4 sections · 2 min readBy Dezső Mező · Published April 22, 2026.mdWebPerformanceCWVChromiumSEO

The Speculation Rules API is probably the biggest quiet win of 2024-26 web performance. Add a small JSON block to your HTML, Chromium prerenders the next-likely page. When the user clicks, the navigation is near-instant. And it costs zero JS bundle size.

01What it does

Two modes: 'prerender' (full render into a hidden tab) and 'prefetch' (fetch only). Prerender is more aggressive · the page is live when clicked. Prefetch is cheaper · the HTML is warm but needs to render on activation.

02The config we ship

<script type='speculationrules'>
{
  'prerender': [{
    'source': 'document',
    'where': { 'href_matches': '/*' },
    'eagerness': 'moderate'
  }],
  'prefetch': [{
    'source': 'list',
    'urls': ['/blog', '/services', '/projects']
  }]
}
</script>

Eagerness 'moderate' triggers on hover (200ms pre-click). 'Eager' triggers immediately on list. 'Conservative' only on mouse-down. Moderate is the right default · it feels instant without blowing the per-origin prerender budget.

03Real numbers

Nav LCP · 1.2s -> 0.05s on prerendered target.
Nav INP · 180ms -> 35ms.
Prerender-hit rate in production · ~75% on moderate eagerness.

04One gotcha

Prerender runs client-side JS immediately · including analytics. GA4, Segment, and Amplitude all dedupe, but some older trackers double-count. Add the 'prerendering' check to your analytics init if you use anything custom.

Ship it. 20 lines of config, 200ms-600ms INP win on nav, 0 JS bundle cost. We now default to this on every Next.js site we build.

What to take away

The Speculation Rules API (Chromium) prerenders navigation targets on hover or list. Near-instant nav, measurable LCP / INP win, zero JS-bundle cost. The production-safe config we default to, the one gotcha worth knowing.

We build this for clientsWeb performance

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