Definition
INP (Interaction to Next Paint) is the Core Web Vitals metric that replaced FID in March 2024. It measures the latency of all user interactions (clicks, taps, keyboard inputs) during a browsing session and retains the worst interaction as the representative score of page responsiveness. Google recommends an INP below 200 milliseconds for a good experience. Unlike FID which only measured the first interaction, INP provides a comprehensive view of page responsiveness throughout the visit. To optimize INP, you need to reduce long JavaScript task durations, use code splitting, avoid forced synchronous layouts, and minimize main thread work. INP is measurable via Chrome DevTools, Web Vitals, and the CrUX report.
Key Points
- Replaced FID as a Core Web Vitals metric since March 2024
- Recommended threshold: less than 200 milliseconds
- Measures the worst interaction latency across the entire user session
Practical Examples
Slow form
A contact form takes 400ms to respond after clicking Submit. Code optimization reduces the INP to 150ms.
Navigation menu
A JavaScript-animated mega-menu generates an INP of 350ms. Switching to pure CSS animations brings the INP down to 90ms.
Frequently Asked Questions
A good INP score is below 200ms. Between 200ms and 500ms, it needs improvement. Above 500ms, it is considered poor.
Reduce JavaScript on the main thread, use Web Workers, optimize event handlers, and prefer CSS animations.
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Last updated: 2026-02-07