Interaction to Next Paint (INP)

Interaction to Next Paint: how long the page takes to visibly answer a tap or a click. Under 200 ms is good.

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Interaction to Next Paint measures responsiveness: from the moment a visitor taps, clicks or presses a key until the browser draws the next frame showing a reaction. The reported value is roughly the slowest interaction of a visit, so one sluggish menu or filter is enough to spoil it. INP replaced First Input Delay as a Core Web Vital in March 2024.

Thresholds and where the number comes from

200 ms or less is good, up to 500 ms needs improvement, more is poor — the limits SiteScan uses to colour the row. INP can only be measured on real interactions, so it appears only in the real-user rows from the Chrome UX Report: the 75th percentile over the last 28 days. A site without enough Chrome traffic has no INP figure at all; the closest lab hint is Total Blocking Time in the Lighthouse rows, which SiteScan calls good up to 200 ms.

How to improve it

Almost always the cause is the main thread being busy with JavaScript.

• Split long tasks and yield back to the browser between chunks, for example with await scheduler.yield() or setTimeout.
• Show visual feedback first, then do the heavy work.
• Ship less JavaScript: drop unused libraries and load third-party scripts late.
• Avoid huge DOMs that make every re-render expensive.