Interaction to Next Paint (INP)

Interaction to Next Paint measures the latency of user interactions from input through event processing to the next paint — the full loop a person actually perceives. It is computed from Event Timing API entries grouped by interactionId, and the page's INP is drawn from its worst qualifying interactions.

INP replaced First Input Delay as a Core Web Vital in March 2024 because FID captured only the delay before the first event handler began running. The documented good threshold is 200 milliseconds at the 75th percentile; long main-thread tasks are the usual cause of failure.