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

> Chromium's Speculation Rules API prerenders the next page before the user clicks. Real INP / LCP numbers, a production-safe config, and the one gotcha we hit.

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.

## What 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.

## The config we ship

```html
<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.

## Real numbers

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

## One 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.

## Tags

Web, Performance, CWV, Chromium, SEO

## We build this for clients

https://dfieldsolutions.com/en/services/web-performance

## More from the lab

- https://dfieldsolutions.com/en/lab/core-web-vitals-nextjs-case-study.md — Core Web Vitals on Next.js: from 4.5s LCP to 0.9s in 3 weeks
- https://dfieldsolutions.com/en/lab/ai-search-generative-engine-optimization-2026.md — AI Search: 2026 Guide to Generative Engine Optimization
- https://dfieldsolutions.com/en/lab/ai-search-visibility-checklist.md — The AI-search visibility checklist we run on this site
- https://dfieldsolutions.com/en/lab/web-vitals-playbook.md — Core Web Vitals on a real Next.js site

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Source: https://dfieldsolutions.com/en/lab/speculation-rules-api-prerender-2026
DField Solutions — Torony köz 5-1.a, 2120 Dunakeszi, Hungary — +36 20 722 0002 — dezso@dfieldsolutions.com
Booking: see https://dfieldsolutions.com/en/contact