On Mon, Jun 23, 2025 at 5:59 PM Yoav Weiss (@Shopify) < yoavwe...@chromium.org> wrote:
> Thanks for improving "moderate"! > > On Mon, Jun 23, 2025 at 10:54 AM 'Domenic Denicola' via blink-dev < > blink-dev@chromium.org> wrote: > >> Contact emailsnhir...@chromium.org >> >> Specification >> https://wicg.github.io/nav-speculation/speculation-rules.html#:~:text=early%20as%20possible.-,%22moderate%22,balance%20between%20%22eager%22%20and%20%22conservative%22.,-%22conservative%22 >> >> Summary >> >> On mobile, "moderate" eagerness speculation rules prefetches and >> prerenders now trigger when a link enters the viewport and passes other >> conditions that indicate that it's more likely to be clicked. The previous >> behavior, of waiting until pointerdown, was the same as "conservative" >> eagerness. This new behavior is more useful as it better reflects author >> intent to be more eager than the "conservative" setting. More detail on >> this and other upcoming improvements to speculation rules eagerness are >> available at >> https://docs.google.com/document/d/1YPbtUPfZIDElzBZNx8IQMzRFvy8oauLG_i1XIr6jgTs/edit?usp=sharing >> . >> > > Are you planning to ship the "simple viewport heuristics", the "complex > viewport heuristics", or both? > This PSA is for "complex viewport heuristics", the new "moderate" behavior. Future PSAs will be used for "eager" (which is "simple viewport heuristics" on mobile.) > > >> >> >> Blink componentInternals>Preload >> <https://issues.chromium.org/issues?q=customfield1222907:%22Internals%3EPreload%22> >> >> Risks >> >> >> Interoperability and Compatibility >> >> The exact definitions of eagerness levels are left vague in the >> specification. ("User agents should enact the candidate if user behavior >> suggests the user may navigate to this URL in the near future. For >> instance, the user might have scrolled a link into the viewport and moved >> the cursor over it for some time.") This change is in line with those >> suggestions. Due to speculation rules' nature as a progressive enhancement, >> it is very hard to depend on the exact heuristic, so varying across browser >> engines, platforms, and browser versions should not pose significant >> interoperability or compatibility risks. As evidence, the heuristic has >> varied across mobile and desktop ever since launch, and this has not caused >> such problems. >> >> >> *Gecko*: Neutral ( >> https://github.com/mozilla/standards-positions/issues/620#issuecomment-2546739520) >> We have not asked Firefox for their thoughts on this specific change. They >> are positive on and implementing prefetching, and will likely make their >> own choices for how to implement each eagerness level. >> >> *WebKit*: No signal ( >> https://github.com/WebKit/standards-positions/issues/54) We've not asked >> Safari for their thoughts on this specific change. They have recently >> indicated a tentative positive position towards conservative-eagerness >> prefetching. >> >> *Web developers*: Positive We've seen several developers re-create this >> viewport-based technique using JavaScript to manually insert and remove >> speculation rules, e.g. in the Quicklink library. >> >> *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 >> >> We have unfortunately not yet made this feature work in DevTools mobile >> emulation mode. That work is tracked in >> https://issues.chromium.org/issues/420724833 and will be worked on as a >> follow up. >> >> Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, Android, and Android WebView)?No >> >> This is only applicable to Android, and speculation rules are not yet >> supported on Android WebView. >> >> Is this feature fully tested by web-platform-tests >> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >> ?No >> >> Because the specification intentionally allows user agent flexibility, >> web platform tests do not capture any specific heuristic here. >> >> Flag name on about://flagsNone >> >> Finch feature namePreloadingViewportHeuristics >> >> Rollout plan(RARE) Experiment users ramp up over time >> >> Tracking bughttps://issues.chromium.org/issues/372053392 >> >> Estimated milestones >> Shipping on Android 138 >> Link to entry on the Chrome Platform Status >> https://chromestatus.com/feature/5079361929347072?gate=5206542386987008 >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com/>. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to blink-dev+unsubscr...@chromium.org. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra-Y5%3DEZ1yUWA8qg152%2BLz5q_jPTUKMMfg866BvO9DgCZg%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra-Y5%3DEZ1yUWA8qg152%2BLz5q_jPTUKMMfg866BvO9DgCZg%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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