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Specification https://github.com/w3c/navigation-timing/pull/188 Summary Websites can indicate that a particular Client Hint <https://wicg.github.io/client-hints-infrastructure/> is critical to the page by including it in a `Critical-CH` HTTP response header. Doing so will trigger a connection restart if the hint listed in the `Critical-CH` HTTP response header could be (but wasn’t) included in the HTTP request initially sent. This intent proposes adding `readonly attribute DOMHighResTimeStamp criticalCHRestart;` to the `PerformanceNavigationTiming` interface. Blink component Blink>PerformanceAPIs>NavigationTiming <https://bugs.chromium.org/p/chromium/issues/list?q=component%3ABlink%3EPerformanceAPIs%3ENavigationTiming> Motivation It’s possible for websites to observe a change in the Navigation Timing <https://github.com/w3c/navigation-timing> related to `responseStart` and `requestStart`, but there is no explicit timestamp that indicates when this occurred. Without that it’s harder for sites to detect the impact that the `Critical-CH` HTTP response header has on connections. Developers (including Akamai) are interested in using this to better understand the impact of User Agent Client Hints / User Agent Reduction. `criticalCHRestart` can only be set for top-level frames, as subresources and iframes ignore `Critical-CH` HTTP response headers. TAG review N/A, this is a small, incremental addition to an existing feature for convenience and the loaded website has other (less convenient) ways to detect a Critical-CH restart. Compatibility & Interoperability We would be the first to implement if approved. Gecko: https://github.com/mozilla/standards-positions/issues/767 WebKit: https://github.com/WebKit/standards-positions/issues/156 Web Developers: Requested by Akamai <https://github.com/w3c/navigation-timing/issues/177> Is this feature fully tested by web-platform-tests? No, but it will be. Tracking bug https://crbug.com/1425910 Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5140317616996352 -- 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 [email protected]. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGpy5DKh-YMxbPGTrV1eRqutkSWbajHpxi1Wjci_sC7w6Mjywg%40mail.gmail.com.
