What Is INP?
What is INP? Interaction to Next Paint looks at how long it takes for the page to provide the next visual update after someone interacts with it. In plain English: when you tap or click, how soon does the interface react in a way you can see?
INP is about responsiveness while using the page — not how long the initial load took. A site can look fully loaded and still feel sluggish if click handlers, heavy JavaScript, or main-thread work delay the visual response to menus, filters, accordions, or "Add to cart" controls.
Because people interact multiple times on a visit, INP reflects interaction delay across the experience rather than a single first-click story. Improving INP often means reducing long tasks on the main thread, deferring non-critical script work, and keeping interactive controls lightweight.
Why It Matters
Frustration is not only about waiting for a blank screen. It is also about tapping a button and wondering if anything happened. Slow interactions erode trust and increase abandoned forms, menus, and checkouts.
For business owners, INP separates "page opened" from "page feels usable." That distinction matters when a redesign looks polished in screenshots but feels sticky on real phones — a common pattern when third-party scripts and complex widgets pile up after launch.
Where You Encounter It
A filter sidebar on a catalog page looks ready. Each filter tap waits noticeably before the UI updates because a large script does expensive work on every click. Visitors may abandon filtering even though the initial LCP looked acceptable. Trimming or deferring that work improves INP without changing the visual design.
Common Misunderstandings
- If the page loads quickly, interactions must be fine. Initial load and interaction responsiveness are related but different problems.
- INP only matters on homepage load. It concerns interactions throughout the visit — forms, menus, carts, and other controls included.