Interaction to Next Paint Changes in Chrome 127

Enable EventTimingKeypressAndCompositionInteractionId by default

Keypress entries are now assigned an interactionID in event timing.
When under composition (IME, virtual keyboard), interactionID is now also exposed to keydown & keyup events (was only exposed to input events).
Keydown events are no longer buffered and delayed reporting until their corresponding keyup events. InteractionIDs for keydown events are now generated upfront (was generated on keyup).

Note: this experiment was first landed in Chrome 123: Expose interactionId to Keypress & keydown/up under composition

How does this affect a site's metrics?

While there is no real effect on keyboard interactions in UX, there may be a measurement shift because INP also measure keypress now; however, the overall site's INP is usually not impacted as INP measures the slower(high percentile) interaction durations and keyboard interactions are usually fast.

Enable EventTimingFallbackToModalDialogStart by default

Event timing was measuring the arbitrarily long user input waiting time on synchronous javascript modal dialogs (eg. alert(), print(), confirm(), etc..) and would report it as part of the processing time. This is because synchronous modal dialogs paused the event-damaged frame to be presented until after users close the dialog. However, showing the modal dialog itself is already a kind of visual feedback to users and users would sense it as a way of page responding. Thus, in event timing, we are adding a concept of alternative end point (other than frame presentation) for duration measurement that represents user-sensed page responding. Modal dialogs that interfere with event timing entries is one; page visibility change is another.

Note: this experiment was first landed in Chrome 123: Handle modal dialog interference

How does this affect a site's metrics?

Pages employing javascript modal dialogs may see a decrease on INP.

When were users affected?

Chrome 127 was released the week of July 23, 2024.