LGTM1 On Wed, Dec 10, 2025 at 10:52 AM Chromestatus < [email protected]> wrote:
> *Contact emails* > [email protected], [email protected], [email protected] > > *Explainer* > > https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/PerformanceNavigationTiming%20for%20User%20Agent%20Launch/explainer.md > > *Specification* > https://w3c.github.io/navigation-timing/#sec-performance-timing-confidence > > *Design docs* > > > https://docs.google.com/document/d/1D6DqptsCEd3wPRsZ0q1iwVBAXXmhxZuLV-KKFI0ptCg/edit#heading=h.7nki9mck5t64 > > *Summary* > Web applications may suffer from bimodal distribution in page load > performance due to factors outside of the application’s control. For > example, when a user agent first launches in a “cold start” scenario, it > must perform many expensive initialization tasks that compete for system > resources. Browser extensions can also affect performance, since some > extensions run additional code on every page you visit, increasing CPU > usage and slowing response times. Likewise, when a machine is already busy > with intensive tasks, web pages may load more slowly as a result. In these > scenarios, content the web app attempts to load will be in competition with > other work happening on the system. This makes it difficult to detect if > performance issues exist within web applications themselves, or because of > external factors. Teams we have worked with have been surprised at the > difference between real-world dashboard metrics and what they observe in > page profiling tools. Without more information, it is challenging for > developers to understand if (and when) their applications may be > misbehaving or are simply being loaded in a contended period. A new > ‘confidence’ field on the PerformanceNavigationTiming object will enable > developers to discern if the navigation timings are representative for > their web application. > > *Blink component* > Blink>PerformanceAPIs>NavigationTiming > <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EPerformanceAPIs%3ENavigationTiming%22> > > *Web Feature ID* > Missing feature > > *Motivation* > When a user agent first launches (a "cold start" scenario), it must > perform many expensive initialization tasks that compete for resources on > the system. Consequently, web applications may suffer from bimodal > distribution in page load performance. Content they attempt to load will be > in competition with other initialization work. This makes it difficult to > detect if performance issues exist within web applications themselves, or > because of a user-agent-generated condition of high resource contention. > This is particularly a pain point for pinned PWAs (Progressive Web Apps) > that will often require a cold start of the user agent, and teams we have > worked with have been surprised at the difference between real-world > dashboard metrics and what they observe in page profiling tools. Without > more information, it is challenging for developers to understand if (and > when) their applications may be misbehaving or are simply being loaded in a > contended period. To address this, we propose adding new information to > existing Web Performance APIs. > > *Initial public proposal* > > https://discourse.wicg.io/t/proposal-user-agent-launch-type-in-performancenavigationtiming/5875 > > *TAG review* > https://github.com/w3ctag/design-reviews/issues/878 > > *TAG review status* > Issues addressed > > *Origin Trial Name* > PerformanceNavigationTiming confidence > > *Chromium Trial Name* > PerformanceNavigationTimingConfidence > > *Origin Trial documentation link* > > https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/PerformanceNavigationTiming%20for%20User%20Agent%20Launch/explainer.md > > *WebFeature UseCounter name* > kPerformanceNavigationTimingConfidence > > *Risks* > > > *Interoperability and Compatibility* > None. > > *Gecko*: No signal ( > https://github.com/mozilla/standards-positions/issues/1191) > > *WebKit*: No signal ( > https://github.com/WebKit/standards-positions/issues/469) > > *Web developers*: Positive ( > https://issues.chromium.org/issues/40255844#comment10) Positive feedback > from WebPerfWG. > https://w3c.github.io/web-performance/meetings/2025/2025-11-TPAC/index.html#h.jgi0mlvusons > > *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? > *No information provided* > > > *Debuggability* > *No information provided* > > *Will this feature be supported on all six Blink platforms (Windows, Mac, > Linux, ChromeOS, Android, and Android WebView)?* > Yes > > *Is this feature fully tested by web-platform-tests > <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* > Yes > > third_party/blink/web_tests/http/tests/misc/performance-navigation-timing-entry-confidence.tentative.html > > *Flag name on about://flags* > *No information provided* > > *Finch feature name* > PerformanceNavigationTimingConfidence > > *Rollout plan* > Will ship enabled for all users > > *Requires code in //chrome?* > True > > *Tracking bug* > https://bugs.chromium.org/p/chromium/issues/detail?id=1413848 > > *Estimated milestones* > Shipping on desktop 145 > Origin trial desktop first 136 > Origin trial desktop last 139 > Origin trial extension 1 end milestone 142 > DevTrial on desktop 135 > Shipping on Android 145 > Origin trial Android first 136 > Origin trial Android last 139 > DevTrial on Android 135 > Shipping on WebView 145 > > *Anticipated spec changes* > > Open questions about a feature may be a source of future web compat or > interop issues. Please list open issues (e.g. links to known github issues > in the project for the feature specification) whose resolution may > introduce web compat/interop risk (e.g., changing to naming or structure of > the API in a non-backward-compatible way). > *No information provided* > > *Link to entry on the Chrome Platform Status* > https://chromestatus.com/feature/5186950448283648?gate=6507865714458624 > > *Links to previous Intent discussions* > Intent to Prototype: > https://groups.google.com/a/chromium.org/g/blink-dev/c/o0F7nBKsgg0/m/bJSp3ekfAAAJ > Intent to Experiment: > https://groups.google.com/a/chromium.org/g/blink-dev/c/FYsfp0OsMko/m/WbhUrqSqAQAJ > Intent to Extend Experiment 1: > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6091e78f-7c77-4ed3-9559-eb660a14dfb7n%40chromium.org > > > 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 [email protected]. > To view this discussion visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6939c150.710a0220.1d2509.07c8.GAE%40google.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6939c150.710a0220.1d2509.07c8.GAE%40google.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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