Web-Facing Change PSA: ServiceWorker support for Speculation Rules Prefetch
Hiroshige Hayashizaki
Contact emails
Specification
https://wicg.github.io/nav-speculation/prefetch.html
Design docs
https://docs.google.com/document/d/192ZLkKcaUE_9Qt8bW9OZLViEEbtxOAgq5WYR87m79IE/edit?usp=sharing
Summary
This feature enables ServiceWorker-controlled prefetches, that is a speculation rules prefetch to URLs controlled by a Service Worker. Previously, the prefetch is cancelled upon detecting a controlling Service Worker, thus subsequent navigation to the prfetch target is served by the non-prefetch path. This feature will enable the prefetch request to go through the Service Worker's fetch handler and the response with the Service Worker interception is cached in the prefetch cache, resulting in a subsequent navigation being served by the prefetch cache. Please use the enterprise policy PrefetchWithServiceWorkerEnabled to control this feature.
Blink component
Risks
Interoperability and Compatibility
This is a bug fix to the existing speculation rules prefetch feature, and as such inherits the same interoperability status as that feature: Gecko is implementing, and WebKit is silent. We are ensuring the specification is fully updated and the test suite is exhaustive, so that as Gecko implements they can get the same behavior.
This does make more prefetches succeed when they would have previously failed, which is a behavior change. But we do not anticipate it being a significant compatibility risk. The explainer document [1] contains more details on exactly what web developers will see.
Gecko: Neutral (https://github.com/mozilla/standards-positions/issues/620#issuecomment-2546739520)
WebKit: No signal (https://github.com/WebKit/standards-positions/issues/54)
Web developers: Strongly positive Service workers are the top actionable reason for prefetch failure, indicating many web developers are running into this issue. (Behind non-actionable ones like battery saver or preloading disabled.) We've also heard directly from several sites that this has been an adoption blocker.
Other signals:
WebView application risks
Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?
None
Debuggability
None
Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?
No
Android WebView does not yet support prefetch
Is this feature fully tested by web-platform-tests?
Yes
Flag name on about://flags
None
Finch feature name
PrefetchServiceWorker
Rollout plan
(RARE) Experiment users ramp up over time
Requires code in //chrome?
False
Tracking bug
https://issues.chromium.org/40947546
Estimated milestones
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/4996410105397248?gate=6656927492472832
This intent message was generated by Chrome Platform Status.