Overview
This page is the atomic definition. The deep-dive lives at core-web-vitals.
Definition
INP (Interaction to Next Paint) is the Core Web Vital that measures responsiveness across every click, tap, and key press on a page. It reports the longest interaction latency at the 75th percentile of real users over a 28-day field window. The “good” threshold is under 200 milliseconds; “needs improvement” is 200 to 500 ms; “poor” is 500 ms or more. INP replaced First Input Delay (FID) in March 2024.
When it applies
Use INP as the responsiveness budget for any interactive page. It surfaces long JavaScript tasks, hydration cost, and third-party script blocking that single-interaction metrics miss.
Example
A React app hydrates the full page on load and ships INP 420 ms. Splitting into Astro islands and gating analytics behind interaction drops INP to 160 ms.
Related concepts
- core-web-vitals - the umbrella metric set INP belongs to.
- react-performance - hydration and long-task patterns that move INP.
- page-speed - the broader speed picture, including TTFB and FCP.
- lcp - the loading metric, scored on a separate budget.
- cls - the layout-stability metric, scored on a separate budget.
Citing this term
See INP (Interaction to Next Paint) (llmbestpractices.com/glossary/inp).