Intent to Extend Experiment: Declarative Performance Observer

[Chromestatus]

Contact emails

sisid...@chromium.org

Explainer

https://github.com/explainers-by-googlers/declarative-performance-observer

Specification

No information provided

Summary

The Declarative Performance Observer proposes a reliable browser-resident telemetry system that reports of performance metrics from navigation initiation to page termination. By using a declarative HTTP response header, it ensures that data is captured even in scenarios where the request failed due to the network error or the renderer process is killed by the OS.

Blink component

Blink>PerformanceAPIs

Web Feature ID

performance

TAG review

https://github.com/w3ctag/design-reviews/issues/1285

TAG review status

Pending

Origin Trial Name

Declarative Performance Observer

Goals for experimentation

The main goal of the Declarative Performance Observer Origin Trial is to validate the reliability and stability of this new browser-resident telemetry system in production. It aims to quantify previously unmeasurable losses, such as early navigation failures occurring before JavaScript execution and abrupt session terminations from process crashes, to establish an accurate reliability baseline.

Chromium Trial Name

DeclarativePerformanceObserver

Origin Trial documentation link

https://github.com/explainers-by-googlers/declarative-performance-observer

WebFeature UseCounter name

kDeclarativePerformanceObserver

Risks

Interoperability and Compatibility

No information provided

Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1458)

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/725)

Web developers: No signals

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.

Reason this experiment is being extended

This Origin Trial was initially configured for M151–M155. During this trial, Chromium transitioned from a 4-week to a 2-week release cadence starting with M153 (September 2026). As a result of this mid-trial transition, M151–M155 provided only 14 calendar weeks of stable experimentation instead of the expected 20–24 weeks. Also, our primary Origin Trial partner experienced unexpected rollout delays, preventing the collection of real-world feedback to validate our core experimentation goals.

Ongoing technical constraints

None.

Debuggability

Reports queued via the Reporting API are visible in DevTools.

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?

Yes

Flag name on about://flags

declarative-performance-observer

Finch feature name

DeclarativePerformacneObserver

Requires code in //chrome?

False

Tracking bug

https://crbug.com/505208781

Launch bug

https://launch.corp.google.com/launch/4465220

Estimated milestones

Origin trial desktop first	151
Origin trial desktop last	155
Origin trial extension 1 end milestone	161
Origin trial Android first	151
Origin trial Android last	155
Origin trial WebView first	151
Origin trial WebView last	155

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6594955352080384?gate=5196782412890112

Links to previous Intent discussions

Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/69f31432.050a0220.3ab19.0b38.GAE%40google.com
Intent to Experiment: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6a6078b0.68e56e23.371e2.01d5.GAE%40google.com

This intent message was generated by Chrome Platform Status.

[Yoav Weiss (@Shopify)]

LGTM to extend experimentation until M161 (inclusive).

The originally requested time was shorter than our "standard" 6 month experimentation period, therefore extending to 161 makes sense to leave partners enough time to adopt and actually experiment.

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