What Is INP?
Interaction to Next Paint (INP) replaced First Input Delay (FID) as a Core Web Vital in March 2024. It measures the time from when a user interacts with a page (click, tap, key press) to when the browser renders the next frame reflecting that interaction. Unlike FID (which only measured the first interaction), INP measures all interactions and reports the worst one. Good INP is under 200ms; poor is over 500ms.
Why INP Matters
INP measures real-world responsiveness. A page that takes 800ms to respond to a button click feels sluggish and broken. INP captures this experience across the entire page session, making it a more comprehensive responsiveness metric than FID was.
How to Improve INP
Reduce JavaScript execution time by breaking long tasks into smaller chunks. Use requestAnimationFrame and requestIdleCallback to defer non-critical work. Minimize main thread blocking. Optimize event handlers to respond quickly. Use web workers for heavy computation.
📖 Related Article: Core Web Vitals Guide — Read our in-depth guide for practical examples and advanced techniques.
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