 What is Interaction to X-Paint? To answer that, here's the INP demo page. I've set it to randomly clog up the main thread with long blocking tasks. You can see their effect in this animation, struggling and failing to run smoothly. If I take a performance trace, you can see them visualized in the performance panel, each long task taking hundreds of milliseconds, disrupting everything else in the main thread. But right now, the INP value is zero. That's because I haven't actually interacted with the page yet. As I click and type, the user experience feels really laggy. It takes a noticeable amount of time for what I type to appear on the screen. Even though the event listers themselves are fast, they're interrupted by those background long tasks, like potholes on a road. So that's one example of what INP measures, the slowest response time to user interactions.