Interaction to Next Paint (INP)
Definition
Interaction to Next Paint (INP) measures how quickly a page visibly responds after a click, tap or key press, across the whole visit. Google rates an INP of 200 milliseconds or less as good. It replaced First Input Delay as a Core Web Vital.
INP looks at every interaction during a visit and reports a value close to the slowest one, so a single sluggish menu, filter or booking widget can fail an otherwise fast page. It is measured on real visits, and Search Console reports groups of similar pages, so one slow widget shows up as a block of failing addresses. First Input Delay, the metric it replaced, judged only the first interaction, so a report that cites it as current is out of date.
The cause is usually JavaScript competing for the browser's attention at the moment someone taps. Tag managers, chat widgets, analytics, ad pixels and booking plugins each add work, and the cost shows up as a delay between the tap and the screen changing. Remove tags nobody reads, delay non-essential scripts until the visitor has interacted, and break long tasks into smaller ones.
A WhatsApp button that responds slowly to a tap is an INP problem and a lost enquiry at the same time. Find the slow interaction by using the page on a mid-range phone and then recording a trace in Chrome's developer tools, because the Search Console report says which pages are slow but not which tap.
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