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Performance

Interaction to Next Paint

INP

Portrait of Robert Klimant, co-founder of Roelu Studio
Robert KlimantCo-founder

What is Interaction to Next Paint?

Interaction to Next Paint (INP) is the Core Web Vital that measures how responsive a page feels when a visitor interacts with it. It tracks the delay between a click, tap, or keypress and the next visual update the browser paints. Google's passing threshold is under 200 milliseconds. Between 200 and 500ms needs improvement; over 500ms is poor. INP replaced First Input Delay in March 2024.

Why it matters

INP is the metric that catches sites that look fast but feel sluggish. The page loaded in two seconds, but you click the menu and nothing happens for half a second. That half-second is INP. The usual cause is too much JavaScript running on the main thread — analytics scripts, A/B test platforms, chat widgets, marketing pixels all fighting for the browser's attention. The buyer's experience: they tap, the page hesitates, they tap again. Trust evaporates in the gap. Most scale-up sites we audit fail INP not because the code is bad, but because nobody is auditing what their growth team has stacked on top of it.

How it works

The browser measures the time from every interaction — click, tap, keypress — to the next frame painted on screen. It reports the worst interaction on the page (roughly) as the INP score. To improve INP, you trim third-party scripts, break long JavaScript tasks into smaller chunks, defer non-essential work until after the page is interactive, and move heavy computation off the main thread using web workers. A well-built modern site usually lands under 100ms. When INP is in the red, the fix often starts with auditing the marketing stack: remove what nobody is using, defer what is not critical, and consolidate the rest.

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