What interactions are measured as part of Interaction to Next Paint?
Interaction to Next Paint (INP) is a Core Web Vital metric that measures how quickly a webpage responds to user interactions. It measures the time between the start of the interaction and the first visual update resulting from that interaction.
Only three types of interactions are measured as part of INP:
- Mouse clicks
- Touchscreen taps (on mobile devices)
- Key presses (physical or onscreen keyboard)
INP does NOT measure other types of interactions, including:
- Scrolling (whether with a mouse or finger)
- Zooming
- Hovering
What about forms? Are form submissions measured as part of INP?
It depends on if the form response loads a new page or not.
For example, let’s say a user clicks, taps or presses Enter to initiate a form submission. The website processes the data and then shows a confirmation message on the same page. The browser does not load a new page. In this case, the interaction will be measured as the time between triggering the submit button and the display of confirmation the message.
Alternatively, if the submission takes the user to a new URL to view a confirmation or thank you page, that interaction will not be measured by INP. This is because the new page load ends the current page’s lifecycle and resets performance measurement.
There are two key concepts to keep in mind:
1) INP measures what happens within the same page
Any interaction that loads a new page won’t track as part of INP. (That new page load will be measured in other ways, like LCP.)
2) INP measures discrete events vs. continuous events
- Discrete events happen at a specific, single point in time and immediately causes a change. You turned a light switch on or off.
- Continuous events happen over a span of time and the changes happen gradually. You gradually turned the volume up or down.
Key takeaway: when assessing and optimizing INP, pay attention to discrete, one-time events that happen as a result of clicks, taps and typing.
Learn more about Core Web Vitals metrics. Or, for more about website speed, check out my book Speed Metrics Guide.
