Thanks for pushing this forward, y'all. We're eager to try it out here at MSFT!
Best, Alex On Wednesday, March 18, 2026 at 4:22:06 AM UTC-7 Yoav Weiss wrote: > LGTM to experiment 147 to 152, inclusive > > This is a long-awaited feature, and it was thoroughly discussed in the > WebPerfWG > > On Wed, Mar 18, 2026 at 12:14 PM Chromestatus < > [email protected]> wrote: > >> *Contact emails* >> [email protected] >> >> *Explainer* >> https://github.com/WICG/container-timing >> >> *Specification* >> https://WICG.github.io/container-timing >> >> *Design docs* >> >> https://github.com/WICG/container-timing >> >> *Summary* >> The Container Timing API enables monitoring when annotated sections of >> the DOM are displayed on screen and have finished their initial paint. A >> developer will have the ability to mark subsections of the DOM with the >> containertiming attribute (similar to elementtiming for the Element Timing >> API) and receive performance entries when that section has been painted for >> the first time. This API will allow developers to measure the timing of >> various components in their pages. >> >> *Blink component* >> Blink>PerformanceAPIs >> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EPerformanceAPIs%22> >> >> *Web Feature ID* >> *No information provided* >> >> *Search tags* >> performance <http:///features#tags:performance>, container >> <http:///features#tags:container>, timing <http:///features#tags:timing> >> >> *TAG review* >> https://github.com/w3ctag/design-reviews/issues/1034 >> >> *TAG review status* >> Issues addressed >> >> *Goals for experimentation* >> During this Origin Trial, we are primarily looking to gain insight into: >> ## The attribute-based instrumentation model - Usage patterns of >> `containertiming` - Frequency and purpose of `containertiming-ignore` - >> Number of annotated elements per page ## PerformanceObserver integration - >> Adoption of PerformanceObserver with container-timing - Whether developers >> batch-observe or use targeted observation - Whether buffering behavior >> meets developer expectations ## Entry shape and timing semantics - Whether >> the exposed timing values align with developer expectations relative to LCP >> and Element Timing - Whether additional metadata fields are needed - >> Whether any fields appear unused or redundant ## Edge cases and ergonomics >> - Nested containers - Dynamically inserted elements - Interaction with >> visibility changes and layout shifts >> >> *Origin Trial documentation link* >> >> https://blogs.igalia.com/dape/2026/02/10/container-timing-measuring-web-components-performance >> >> >> *Risks* >> >> >> *Interoperability and Compatibility* >> *No information provided* >> >> *Gecko*: Positive ( >> https://github.com/mozilla/standards-positions/issues/1155) Firefox are >> positive and are working on an implementation: >> https://phabricator.services.mozilla.com/D279373 >> >> *WebKit*: Neutral ( >> https://github.com/WebKit/standards-positions/issues/442) >> >> *Web developers*: No signals >> >> *Other signals*: >> >> *Ergonomics* >> Performance overhead only happens when enabling, any overhead is low >> because we piggy back on DOM-traversals which are already happening. >> >> *Activation* >> The feature is consistent with other Performance APIs that work on the >> Performance Timeline. This feature can't be polyfilled properly, there has >> been an attempt (see Explainer) but that has high resource usage. Today all >> the documentation lives in the explainer, we will hope to promote this more >> once it is exposed to the wider development community. >> >> *Security* >> >> https://github.com/WICG/container-timing/?tab=readme-ov-file#security-and-privacy >> >> *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* >> >> >> *Ongoing technical constraints* >> None >> >> *Debuggability* >> Container Timing entries can be printed to the developer console from the >> PerformanceObserver. The attributes are also observable in the Elements >> Panel. This feature has basic support from DevTools. >> >> *Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, Android, and Android WebView)?* >> Yes >> This feature is implemented in Blink and isn't subject to any platform >> specific APIs >> >> *Is this feature fully tested by web-platform-tests >> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >> Yes >> >> https://wpt.fyi/results/container-timing/tentative?label=experimental&label=master&aligned >> >> *DevTrial instructions* >> >> https://github.com/WICG/container-timing?tab=readme-ov-file#chrome-canary-and-chrome-beta >> >> *Flag name on about://flags* >> enable-experimental-web-platform-features >> >> *Finch feature name* >> ContainerTiming >> >> *Requires code in //chrome?* >> False >> >> *Tracking bug* >> https://issues.chromium.org/issues/382422286 >> >> *Measurement* >> >> https://chromestatus.com/metrics/feature/popularity#V8Element_ContainerTimingIgnore_AttributeGetter >> >> https://chromestatus.com/metrics/feature/popularity#V8Element_ContainerTiming_AttributeGetter >> >> https://chromestatus.com/metrics/feature/popularity#ContainerTimingObserverRegistered >> >> *Estimated milestones* >> Origin trial desktop first 147 >> Origin trial desktop last 152 >> DevTrial on desktop 145 >> Origin trial Android first 147 >> Origin trial Android last 152 >> DevTrial on Android 145 >> Origin trial WebView first 147 >> Origin trial WebView last 152 >> >> *Link to entry on the Chrome Platform Status* >> https://chromestatus.com/feature/5110962817073152?gate=5112674898411520 >> >> *Links to previous Intent discussions* >> Intent to Prototype: >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/672cffcd.2b0a0220.d9f4a.0540.GAE%40google.com >> >> >> 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/69ba8919.050a0220.1bf526.0067.GAE%40google.com >> >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/69ba8919.050a0220.1bf526.0067.GAE%40google.com?utm_medium=email&utm_source=footer> >> . >> > -- 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/0ec20a29-59b4-41e1-b030-936f35bf8a45n%40chromium.org.
