Allow external <script type=speculationrules>

I’m building a project that is a bunch of plain HTML files with plain CSS and JS – there is no build step. I’m deploying this project to a server where I cannot control the headers being sent.

Because I can’t control the headers, I needed to add Speculation Rules by adding the following snippet to each and every HTML file:

<script type="speculationrules">
	{
		"prerender": [{
			"source": "document",
			"where": {
				"href_matches": "/*"
			},
			"eagerness": "moderate"
		}]
	}
</script>

This is very repetitive. I kinda assumed I would be able to do the following to keep things DRY, but turns out this is not possible:

<script type="speculationrules" src="file-with-speculation-rules.json"></script>

Hereby requesting to consider this feature request.

As mentioned on chat, this is possible with plain JS:

<script src="inject-speculation-rules.js" defer></script>

And then have inject-speculation-rules.js contain something like this:

if (HTMLScriptElement.supports &&
    HTMLScriptElement.supports('speculationrules')) {
  const specScript = document.createElement('script');
  specScript.type = 'speculationrules';
  specRules = {
    prerender: [
      {
        urls: ['/next.html'],
      },
    ],
  };
  specScript.textContent = JSON.stringify(specRules);
  console.log('added speculation rules to: next.html');
  document.body.append(specScript);
}

But yeah it seems it would be nice to be able to do this directly.

Intent to prototype in Chrome: https://groups.google.com/a/chromium.org/g/blink-dev/c/7ph2PcVZm6M

Microsoft (Office Online) finds this enhancement interesting and thinks it sounds like a great addition to speculation rules!

I came here with the same issue. Working on a site with pure HTML, CSS and JS. No build, no frameworks.

Would be great to have external speculation rules.

This goes for all new APIs. It gets very repetitive when configuration has to be repeated on every page.

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Allow external <script type=speculationrules> #348

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Allow external <script type=speculationrules> #348

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tunetheweb commented on Dec 6, 2024

tunetheweb commented on Feb 5, 2026

jspurlin commented on Mar 3, 2026

johannesodland commented on Jun 3, 2026

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