INP (Interaction to Next Paint)

For each notable interaction during the lab test, the gap between the start of the interaction and the first frame rendered after it is measured, and the slowest or near-slowest interaction is reported as the final value; under 200ms is good and beyond 500ms is poor.

This metric is the main measure of how responsive a page is to real user interaction, showing whether buttons and elements react nimbly after initial load, or whether the user hits a brief freeze after clicking them.

When INP climbs, it means heavy JavaScript code has kept the browser's processor busy for a long stretch, stalling the user's commands; this frustrating delay leaves customers with a sense of inefficiency and severe sluggishness. From a business angle, slow interactions directly block completion of critical flows like checkout, signup, or form submission, and sharply drag down conversion rate. Watching this metric helps product managers make sure their product isn't just fast to load, but stays alive, smooth, and fully responsive under the user's fingertips.