v152 · Origin trial / performance

Speculation Rules - moderate viewport heuristics controls

Current viewport heuristics for speculation rules don't give any room for developer experimentation. This experimental feature will provide such controls, and enable developers to figure out if different heuristics parameters give them better results than the default ones. This is a feature only aimed at experimentation, and there are no plans to ship it as is.

concepts

  1. Heuristic Builder

    Create and inject a real speculationrules block with the experimental top-level object.

  2. Candidate Ranker

    Explore the documented distance, visible-area, threshold, and delay algorithm.

  3. Prefetch Observer

    Inject moderate rules and inspect resource timing without claiming a prerender occurred.

why it shipped

Temporary developer controls let sites experiment with the mobile moderate-eagerness viewport heuristic before Chromium chooses better defaults.

references