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Explainer No specific explainer, but all the details are here: https://chromestatus.com/feature/5087526916718592?context=myfeatures https://bugs.chromium.org/p/chromium/issues/detail?id=1345207&q=5%20minute&can=3 Spec This feature was never specified! A new PR to the HTML spec to clarify how prefetch is supposed to work does not include this removed feature: https://github.com/whatwg/html/pull/8111 Summary - Currently, when a document includes <link rel=prefetch> and then a resource tries to consume it, cache-control semantics (max-age, no-cache etc) are ignored for 5 minutes. - This was originally introduced when prefetches were meant for cross-origin navigations (think search engine results), as the prefetching page had no control over the caching semantics of the prefetched page - Since introducing partitioned caching, <link rel=prefetch> no longer works for cross-origin navigation anyway, so that initial use-case is irrelevant. - Data from UMA shows <https://docs.google.com/spreadsheets/d/1iGYYbwaXUSxvPHH7Cl-IuxmIH6eMHDgWTLpH2pwDCUA/edit?usp=sharing> that the vast majority of prefetch reuses don't benefit from this - only *0.05%*. The rest are either anyway within the cache max-age, outside the 5 minutes, or reused past the first time. This makes this a niche feature that apart from adding a bit of confusion to the mix does very little. - Additional supporting data from HTTP archive <https://docs.google.com/spreadsheets/d/1N7fHysHI-Yx1taBppcGN3Z_DK8Y--fc4XZmtesIrMp4/edit#gid=0> shows that the web dev community is not using prefetch for cross-origin navigations, but rather mainly for same-origin early fetching of styles and scripts (only *4%* of pefetches are for cross-origin navigations). - The data shows that <link rel=prefetch> transitioned from being a feature for search-type pages into a feature for home/landing pages: e.g. you have a very fast landing page without scripts and a link to the full web-app page, and you prefetch the scripts and style of the heavy app to make it load faster once you click the link Link to “Intent to Prototype” blink-dev discussion Link to the blink-dev discussion about implementation. Here’s a link to the Google Groups page for blink-dev <https://groups.google.com/a/chromium.org/g/blink-dev/c/eduycCpm5ws/m/ddZufPhcAgAJ> . Link to Origin Trial feedback summary There was no origin trial. Users would barely feel the impact of this. Is this feature supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)? Yes Demo link N/A Debuggability Web devs can see the impact of this in their network panel. Measurement It's a removal, and current use of the feature is marginal at best (potentially arbitrary and inconsequential). Risks Interoperability and Compatibility This fix is interoperable with firefox, and Safari folks are positive <https://github.com/WebKit/standards-positions/issues/114> about implementing fetch with the proposed behavior (without the 5-minute rule); Ergonomics It's a feature removal that very few rely on. The new speculation-rules prefetch <https://chromestatus.com/feature/5740655424831488> should be a replacement for cross-origin navigational prefetch. Activation The very few developers who currently rely on the 5-minute can explicitly make the same behavior work using Cache-Control headers. Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_platform_tests.md>? Link to test suite results from wpt.fyi. PR for prefetch behavior pending spec merging: https://github.com/web-platform-tests/wpt/pull/35707 Entry on the feature dashboard <http://www.chromestatus.com/> https://chromestatus.com/feature/5087526916718592 -- 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 on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAJn%3DMYa7YN%3DdePW5E9LQ2Qpo72r2h3m%3DVKdXfTg910U7AC51_w%40mail.gmail.com.
