1. Glossary
  2. Interaction to Next Paint (INP)

Interaction to Next Paint (INP)

Interaction to Next Paint (INP) measures the responsiveness of a website to user interactions (for example, when they click a link, tap on a button, or use a custom, JavaScript-powered control).

INP was designed by Google as one of the Core Web Vital metrics, replacing First Input Delay (FID) in May 2024. There are two key differences between FID and INP that make INP a more reliable measure of a page's responsiveness:

  • FID measures only the first user interaction, whereas INP considers all user interactions.
  • FID only measures the input delay of the interaction, whereas INP measures for a longer period: beginning at the input delay, followed by the time it takes to process event handlers, and the browser's presentation time until the browser has painted the next frame.

INP measures the worst length of time (minus some outliers), in milliseconds, between the user interaction on a web page and the next frame presentation after that interaction is processed. Scrolling and zooming are not included in this metric. INP is calculated using the