Thanks for the update. LGTM to continue experimenting from M147 to M149
inclusive.
On 4/1/26 4:14 p.m., Michal Mocny wrote:
(The automated email removed my message formatting, and its a bit
confusing to read through the full history. For your benefit, here is
a formatted copy focusing on the new request)
Requesting a 3 milestone extension to the Origin Trial for this
feature (m147 - m149).
Reason:
* Provide developers the opportunity to test several significant
changes to the API shape following the most recent Origin Trial
(OT) feedback (details below).
* Also, multiple developers have requested the opportunity to
participate in a new OT period, as they were unable to complete
testing before the previous deadline.
* While we considered moving directly to shipping, the substantial
implementation changes following the first OT will benefit from
another round of developer feedback to ensure a stable launch.
* (We also have remaining specification and documentation work to
complete).
Major changes since the end of the previous OT:
* InteractionContentfulPaint performance entry now reports for ALL
interactions, and reports before the soft navigation performance
entry is emitted.
o I.e. It's a general responsiveness metric as well as a
navigation loading metric.
* Integrated with Event Timing interactions, and both SoftNavigation
and InteractionContentfulPaint now receive an `interactionId`
value to match.
* Added support for `replaceState` and exposed `navigationType` to
the API (a top developer-requested feature change)
Minor changes:
* Adjusted the navigation startTime to match the interaction event
timing startTime (i.e. Event hardware timeStamp).
o This will make reported timings appear larger, but be more
consistent with existing Interaction metrics (and existing
interaction performance measurement tooling).
* Many more "under the hood" improvements further improve detection
rates and paint reporting quality.
Field data results from the latest versions look incredibly promising
(and we hope to share some insights publicly at BlinkOn, soon).
On Wed, Apr 1, 2026 at 3:21 PM Chromestatus
<[email protected]> wrote:
*Contact emails*
[email protected], [email protected], [email protected]
*Explainer*
https://github.com/WICG/soft-navigations
https://github.com/WICG/soft-navigations/blob/main/Design.md
*Specification*
https://wicg.github.io/soft-navigations
*Summary*
Exposes the (experimental) soft navigation heuristics to web
developers, using both PerformanceObserver and the performance
timeline. This feature reports two new performance entries: -
"soft-navigation", for user interactions which navigate the page.
Defines a new timeOrigin to help slice the performance timeline. -
"interaction-contentful-paint", which reports on the loading
performance of interactions (beyond just next paint), used as LCP
for soft-navigations.
*Blink component*
Blink>PerformanceAPIs
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EPerformanceAPIs%22>
*Web Feature ID*
/No information provided/
*TAG review*
https://github.com/w3ctag/design-reviews/issues/879
*TAG review status*
Issues addressed
*Origin Trial Name*
Soft Navigation Heuristics
*Goals for experimentation*
1. Gaining insights on the quality of the heuristic and how it
compares to current heuristics employed, from web developers,
spa-framework authors, and by existing RUM providers; Focusing
specifically on the initial "soft-navigation" reporting and the
"interaction-contentful-paint" loading entries that follow. 2.
Learning if developers find the correlation of various existing
performance entries (i.e. Resource Timings, CLS or INP entries) to
these soft navigation entries more useful than without them.
*Chromium Trial Name*
SoftNavigationHeuristics
*Link to origin trial feedback summary*
https://github.com/WICG/soft-navigations/issues
*Origin Trial documentation link*
https://github.com/WICG/soft-navigations#soft-navigations
*Risks*
*Interoperability and Compatibility*
/No information provided/
/Gecko/: No
signal (https://github.com/mozilla/standards-positions/issues/854)
/WebKit/: No
signal (https://github.com/WebKit/standards-positions/issues/235)
/Web developers/: Strongly positive
https://github.com/WICG/proposals/issues/71#issuecomment-1325856231
https://twitter.com/yoavweiss/status/1575191332775026688
/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/
*Reason this experiment is being extended*
Requesting a 3 milestone extension to this feature. Reason:
provide developers the opportunity to test several significant
changes to the API shape following the most recent Origin Trial
(OT) feedback (details below). Also, multiple developers have
requested the opportunity to participate in a new OT period, as
they were unable to complete testing before the previous deadline.
While we considered moving directly to shipping, the substantial
implementation changes that followed the first OT we think will
benefit from another round of developer feedback to ensure a
stable launch. (We also have remaining specification/documentation
work to do). Major changes since end of previous OT: -
InteractionContentfulPaint performance entry now reports for ALL
interactions, and reports BEFORE soft navigation performance entry
is emitted. I.e. its a general responsiveness metrics as well as a
navigation loading metric. - Integrated with Event Timing
interactions, and both SoftNavigation and
InteractionContentfulPaint now receive an `interactionId` value to
match. - Added support for replaceState, and expose
`navigationType` to the api (top developer requested feature
change) Minor changes: - Adjusted the navigation startTime to
match the interaction event timing startTime (i.e. Event hardware
timeStamp). This will make reported timings look larger, but more
consistent with existing Interaction metrics (and existing
tooling) - Many more "under the hood" improvements that further
improve detection rates and paint reporting quality. Field data
results from the latest versions look incredibly promising (and we
hope to share some insights publicly at BlinkOn, soon).
*Reason this experiment is being extended*
We are still collecting feedback from partners, who are evaluating
the suitability of this API to replace existing ad-hoc methods of
measuring soft navigations, including some who were only recently
able to start experimenting. Additionally, we have made changes to
the heuristics, in response to testing and feedback, to eliminate
some false-positive detections, and better match the behaviour of
real-world single-page apps. Some of these changes initially went
out in Chrome 120, and were refined in Chrome 121; some will be
released with Chrome 122. We'd like to give developers a chance to
experiment with these changes, to help inform any future
adjustments that need to be made. After Chrome 123, we intend to
pause the experiment while we act on all of the feedback, and
decide whether further changes to the heuristics are necessary, or
if the API is in good enough shape to consider shipping.
*Reason this experiment is being extended*
This feature has already gone through two origin trials which
ended in milestone 123 a year ago. We took developer feedback and
communicated with web developers at the end of the trial with the
following status: "The Chrome team are taking time to review the
experiment feedback and consider the next steps for this API. We
want to address some accuracy issues and believe another origin
trial will be required before the feature is ready to progress."
Over the next year we investigated the reasons for the
deficiencies, updated the implementation, and revamped the
proposed API slightly. I have created a description of these
changes here: https://github.com/WICG/soft-navigations/issues/47
Early results (local lab testing, and field histograms in
aggregate) from the current version of the feature shows a
significant improvement from a year ago, and we've gotten positive
anecdotal feedback from some early testers on Canary with
experimental features enabled. Although this feature has already
had 2 Origin trials, because there has been over a year of gap
since the last trial, we request permission for another 6
milestones extension, rather than 3, which are necessary as we
expect it will take developers some time ramp up and collect
sufficient field data to analyze give feedback, and for us to
iterate on this feedback.
*Ongoing technical constraints*
None.
*Debuggability*
/No information provided/
*Will this feature be supported on all six Blink platforms
(Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?*
No
*Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?*
Yes
*Flag name on about://flags*
/No information provided/
*Finch feature name*
SoftNavigationHeuristics
*Requires code in //chrome?*
False
*Tracking bug*
https://bugs.chromium.org/p/chromium/issues/detail?id=1338390
*Estimated milestones*
Origin trial desktop first 139
Origin trial desktop last 144
Origin trial extension 1 end milestone 123
Origin trial extension 2 end milestone 149
Origin trial extension 3 end milestone 123
Origin trial extension 4 end milestone 144
Origin trial Android first 139
Origin trial Android last 144
Origin trial WebView first 139
Origin trial WebView last 144
*Link to entry on the Chrome Platform Status*
https://chromestatus.com/feature/5144837209194496?gate=5090983379337216
*Links to previous Intent discussions*
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfV3qRFx0i-eGJFSzqE8bnbX8XYJCvXAj0LfvO0icPo_jA%40mail.gmail.com
Intent to Experiment:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUb_Gn_5gGy8SnChg5KH2JN57Gv0NhnHN7Q_kH0Aa17CQ%40mail.gmail.com
Intent to Extend Experiment 1:
https://groups.google.com/a/chromium.org/g/blink-dev/c/xxrmKr-6X38/m/48Hri1cnAgAJ
Intent to Extend Experiment 3:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfULP5d3fNCAqeO2gLP56R3HCytmaNk%2B9kpYsC2dj4%3DqoQ%40mail.gmail.com
Intent to Extend Experiment 4:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAEeF2TfyN4LMy2DQwjPrsTekEw8dNXgcqiogvznagjtWyfqixA%40mail.gmail.com
This intent message was generated by Chrome Platform Status
<https://chromestatus.com>.
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