Intent to Prototype: Speculation Rules: prerender-until-script Action

[Chromestatus]

Contact emails

lin...@chromium.org

Explainer

https://github.com/WICG/nav-speculation/blob/main/prerender-until-script.md

Specification

https://wicg.github.io/nav-speculation/prerendering.html#speculation-rule-set-prerender_until_script-rules

Summary

This extends speculation rules to introduce a new action called prerender_until_script. It is designed as an intermediate option between the existing prefetch (which only fetches the main document) and prerender (which fully renders the page and runs all scripts). This new action will fetch and parse a page, discover and download its subresources like images and stylesheets, but will pause all script execution. When the user navigates to the page, it activates, and all the deferred scripts are then executed in order. This allows for a near-instant page load for content-heavy sites without the performance cost or side effects of running analytics or third-party scripts prematurely.

Blink component

Internals>Preload>Prerender

Web Feature ID

speculation-rules

Motivation

The Speculation Rules API provides developers with powerful tools for speeding up navigations, including prefetch for fetching a document and prerender for fully rendering it. The prerender_until_script action complements these existing options by providing a new intermediate choice. It is designed for developers who want to achieve significant performance gains by loading a page and its critical subresources, while also deferring all script execution until the page is actively visited. This action instructs the browser to parse the document and fetch key subresources (e.g., stylesheets, images) discovered by the preload scanner. By stopping before script execution, it offers a low-cost way to prepare the page for a near-instant load, giving developers more granular control over the performance-versus-resource-use tradeoff.

Initial public proposal

https://github.com/WICG/nav-speculation/issues/305

Search tags

speculationrules, prerendering, prefetch, nostateprefetch

Requires code in //chrome?

False

Estimated milestones

No milestones specified

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6324676351623168?gate=6047691830329344

This intent message was generated by Chrome Platform Status.