Ready for Developer Testing: Performance + Event Timing: InteractionCount

[Chromestatus]

Contact emails

mmo...@google.com

Specification

https://www.w3.org/TR/event-timing/#dom-performance-interactioncount

Design docs

No information provided
https://www.w3.org/TR/event-timing/#dom-performance-interactioncount
https://www.w3.org/TR/event-timing/#sec-increasing-interaction-count

Summary

The Event Timing API is part of the Performance Timeline and is used to measure the performance of user interactions. Certain Events will have an interactionId value assigned to them, and this is useful for grouping related interactions based on common physical user inputs or gestures. This feature adds a very trivial performance.interactionCount, which is just the total number of interactions that have occured on the page. In particular, this feature is useful for computing the Interaction to Next Paint (INP) metric value, which requires knowing the total number of interactions in order to compute a high percentile score (p98 for pages with greater than 50 total interactions). This feature has been specced for a long while, was prototypes in Chromium a long time ago but never shipped, is part of Interop 2025, and is already available in other browsers. (Note: there is already a more powerful performance.eventCounts map for specific events, but it is not possible to accurately map event cunts to interaction counts.)

Blink component

Blink>PerformanceAPIs

Web Feature ID

event-timing

Risks

Interoperability and Compatibility

Other browser venders have already shipped this feature as part of the Interop 2025 effort for CWV INP. The main interop risk is that there are existing polyfills for interactionCount in Chromium for INP calculation. However, popular polyfills (such as web-vitals.js) have long been tested to feature detect, given the long experimental web platform implementation in chromium.

Gecko: Shipped/Shipping (https://groups.google.com/a/mozilla.org/g/dev-platform/c/xvv6sxJZc4U/m/JzSSCoxPAgAJ?e=48417069)

WebKit: In development (https://bugs.webkit.org/show_bug.cgi?id=297361)

Web developers: Strongly positive No specific link, but this feature is related to the very popular INP metric definition (and obviates the need for an imperfect polyfill for counting interactions).

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?

n/a

Debuggability

DevTools has existing support for Interactions (real time performance monitor and tracing). Visualizing total interactionCount is not needed, but can be easily found (via literally counting the list of interactions, or just console logs).

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
https://wpt.fyi/results/event-timing/ (several tests, look for interaction-count-*)

Flag name on about://flags

No information provided

Finch feature name

EventTimingInteractionCount

Requires code in //chrome?

False

Availability expectation

Feature is available on Web Platform Baseline within 12 months of launch in Chrome (as part of Interop 2025 for INP)

Adoption expectation

Polyfill already widely adopted (for INP calculation), and feature detection already used.

Estimated milestones

Shipping on desktop	143
DevTrial on desktop	111
Shipping on Android	143
DevTrial on Android	111
Shipping on WebView	143

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).

Already specced in Event Timing API.

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5153386492198912

This intent message was generated by Chrome Platform Status.

[Michal Mocny]

Context: This feature has been implemented behind an experimental status flag for over a year and has had extensive developer testing-- but there was never a dedicated Chrome feature specifically for it created, as it was just part of the larger Event Timing / interactionId (for INP) project.

As part of Interop 2025, other implementers have started to ship this feature and so we want to ship as well.  I expect to send I2S shortly, before the m143 branch, but needed to send this first.  (Not sure if there was a better expedited process)

-Michal