What is INP?
Interaction to Next Paint (INP) measures the time from when a user interacts with a page until the browser responds. INP officially replaced First Input Delay (FID) in 2024.
Why the change?
FID only measured the first interaction. INP evaluates all interactions throughout the visit, providing a more complete view of responsiveness.
How it's measured
INP is calculated as the 90th percentile of the worst interactions. An interaction can be a click, tap, or key press.
Target values
INP below 200ms is good. Between 200ms and 500ms needs improvement. Above 500ms is poor.
Common causes of high INP
Blocking synchronous JavaScript, long tasks on the main thread, complex event listeners, and inefficient DOM rendering.
How to optimize INP
Split long tasks with setTimeout or requestIdleCallback, use Web Workers for heavy processes, implement debouncing on frequent events, and avoid unnecessary reflows.
Conclusion
INP is now a ranking metric you cannot ignore. At Vynta we conduct performance audits focused on Core Web Vitals to ensure the best user experience.