Contact emails
[email protected]

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.

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