Definition
Interaction to Next Paint is a Core Web Vitals metric that measures how quickly a page visually responds after a user interacts with it — a tap, click or key press. For each interaction it records the time from the input to the next frame the browser paints, and the page's INP is (roughly) the worst of these across the visit, so it reflects overall responsiveness rather than a single event.
It replaced First Input Delay, which only measured the delay before processing started; INP measures the whole interaction through to the visible update.
A good INP is generally taken as 200 milliseconds or less; above about 500 milliseconds is poor. It is driven mostly by heavy JavaScript work on the main thread blocking the browser from responding, so it is largely a code-efficiency problem.
In context
For an iGaming affiliate, INP matters on interactive pages — comparison tables with filters, bonus calculators, quiz funnels, odds tools, any page with menus, tabs or accordions — where a sluggish response after a tap is exactly what INP penalises and what frustrates a mobile-majority audience. Content-only pages with little scripting usually pass INP easily; the risk is on the tool and widget pages, and on any page loaded down with third-party tags (analytics, ad, affiliate, chat, consent scripts) competing for the main thread.
The fixes are code-efficiency work: reduce and defer non-essential JavaScript, break up long tasks so the browser can respond between them, minimise third-party script weight and load it late, avoid large layout or rendering work on interaction, and use efficient event handlers. Consolidating tag management and cutting unused scripts often helps most on a typical affiliate site.
INP should be tracked as field data (real users) alongside lab tests, since it depends on real devices and real interaction patterns. For affiliate-facing content, the framing is that INP measures how fast a page responds visibly to user interactions across the visit, that a good score is 200ms or less, that it is mostly caused by heavy main-thread JavaScript and third-party tags, that it is a risk mainly on interactive tool and widget pages, and that the fix is reducing and deferring script work.
Worked example
An affiliate's field data shows its bonus-calculator and comparison-tool pages have a poor INP around 450ms while its content pages pass. Profiling finds long main-thread tasks from an unoptimised widget and several third-party tags.
The team defers non-essential scripts, breaks up the widget's work, and trims tags; INP for those pages drops under 200ms.
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