INP (Interaction to Next Paint)
INP measures how long a page takes to respond visibly to user interactions — a click, tap or key press — and reports the longest interaction observed during a page visit. It has been one of Google's three official Core Web Vitals since March 2024, when it replaced First Input Delay (FID).
In practice
A good INP value is 200 milliseconds or less, assessed at the 75th percentile of real page views, separately for mobile and desktop. What is reported is not the average but the longest interaction observed during a page visit. Unlike FID, which only measured the delay before processing started, INP captures the responsiveness of the whole interaction. Scrolling and zooming expressly do not count as interactions for INP, so the metric does not describe general "jank" but response time to clicks, taps and key presses. Because real interactions are required, INP has no lab value: Lighthouse and PageSpeed Insights report Total Blocking Time (TBT) as a proxy instead. The most common cause of poor INP values is heavy JavaScript execution blocking the browser's main thread. In practice it helps to break long JavaScript tasks into smaller pieces and to remove or defer scripts that are not needed.