Interaction to Next Paint is a Core Web Vitals metric that measures how quickly a page responds visually after user interactions.
It matters because technical issues can prevent great content from being discovered, rendered, indexed, or trusted. Strong technical foundations protect rankings during redesigns, migrations, content expansion, and platform changes.
Example
A filter button may appear unresponsive while a long script blocks the browser from updating the screen. INP helps assess that interaction delay across a visit, so testing only the initial page load misses part of the experience.