IInteraction to Next Paint (INP)

Interaction to Next Paint (INP) measures the time between a user's action—like clicking a button or typing in a form—and the browser's visible response. It replaces First Input Delay (FID) as a core metric for assessing page responsiveness. Rather than just measuring the delay itself, INP captures the full experience: how long the browser takes to process the interaction and display the result.

For business owners, INP directly affects user satisfaction and conversion rates. A slow response makes your site feel unresponsive and broken, even if it's technically working. Users abandon forms, skip purchases, and leave for competitors. Since Google uses INP as a ranking factor, poor performance also damages your search visibility. This matters across all digital properties—e-commerce sites, SaaS platforms, mobile apps, and content-heavy websites all need responsive interactions.

INP works by monitoring every interaction on a page and recording how long each takes. The metric reports the 98th percentile of interactions, meaning the slowest interactions are measured rather than averages. This captures real user frustration points. Poor INP usually stems from heavy JavaScript execution, unoptimised event handlers, or rendering delays. A page might load quickly but still feel sluggish once users try to use it.

Good INP performance requires optimised code, efficient event handling, and smart browser rendering strategies. Developers need to minimise JavaScript blocking, defer non-critical tasks, and use modern frameworks that handle rendering efficiently. Mobile devices are particularly affected because they have less processing power than desktop computers.