What is Interaction to Next Paint?

Understanding Interaction to Next Paint

Interaction to Next Paint, commonly shortened to INP, measures how quickly a page responds visually. It responds after a person interacts with it. Interactions include clicks, taps, and keyboard actions. These actions trigger page behaviour. The metric focuses on the delay before the browser presents the next visual change. This change might open a menu or update a form.

Related glossary terms: INP, Core Web Vitals, Largest Contentful Paint.

INP assesses responsiveness across the page visit. It doesn't rely on one selected interaction. This approach helps reveal occasional delays. A quick initial test might miss these delays. A low INP generally indicates efficient page making. It also shows that JavaScript and the browser main thread work well together.

How Interaction to Next Paint Works, Is Measured, or Is Used?

For each eligible interaction, the browser records when it begins. It also records when the next frame displays. The measured delay can include event-processing time and presentation delay. It can include other work that prevents screen updates. INP normally represents the longest interaction delay during a visit. Some extreme outliers are excluded from the calculation.

Field data usually comes from real visitors. Sources include the Chrome User Experience Report and the web-vitals library. Another source is a Real User Monitoring system. Results are grouped by page URL and visitor experience. They are then classified using accepted thresholds. A page has a good INP at 200 milliseconds or less. It needs improvement above 200 and up to 500 milliseconds. It is poor above 500 milliseconds.

Why Interaction to Next Paint Matters?

Responsive pages provide clearer feedback when people complete important actions. A delayed menu, search filter, checkout control, or booking form can create uncertainty. The page may appear not to have received the input. INP therefore provides a practical signal for interaction quality. It isn't merely a technical score.

INP can also help technical teams prioritise performance work. A poor result may point towards long tasks or excessive script execution. It may also show expensive making or inefficient event handlers. Improving the underlying cause can reduce frustration. It can also support stronger engagement. INP is only one part of overall page experience. It doesn't guarantee higher rankings.

When Interaction to Next Paint Matters Most?

INP matters most on pages where people take repeated actions. These include ecommerce listings, dashboards, calculators, account areas, and online forms. These pages may load their main content quickly. They may still respond slowly after interaction. Testing only the first screen or initial page load can miss problems. It can therefore overlook important usability problems.

Review INP after adding third-party scripts or client-side features. Also review it after adding large interface libraries or complex animations. Compare mobile and desktop results. Device processing power and network conditions can change the experience substantially. Use both controlled testing and field data when possible. Laboratory tests can't reproduce every real visitor's device or input pattern. They also can't reproduce every browsing context.