A Core Web Vitals metric that records the elapsed time from a user’s first interaction until the browser paints the next visual frame.
Web developers and performance analysts reading about web speed optimization or Core Web Vitals metrics.
01What it is and how it works
INP starts timing when a user initiates an interaction that could lead to a visual change, such as clicking a button, tapping a link, or pressing a key. The timer stops when the browser first paints the resulting visual update. If no visual change occurs within 500 ms, the interaction is considered non‑responsive and the metric records the full delay. The metric is collected per interaction and then aggregated to a single value per page load, representing the 75th percentile of observed interaction delays.
INP is a simple measure of how fast a page displays a visual change after a user clicks or taps something. It tells you how responsive the page feels to direct actions.
02What to do about it
Improving INP focuses on reducing the time between a user’s action and the first paint. This involves making UI work that blocks the main thread asynchronous, using efficient CSS animations, and ensuring click handlers do not cause long tasks. Developers should also limit the number of simultaneous animations and avoid heavy JavaScript execution during user input.
- Defer non‑essential scripts until after user interactions.
- Use requestIdleCallback or setTimeout(..., 0) for UI updates that aren’t immediate.
- Replace heavy CSS transitions with will-change and transform for better performance.
- Test with Chrome DevTools Performance panel to spot long tasks.
03How it is measured or noticed
INP is reported by Chrome User Metrics and appears in Lighthouse, PageSpeed Insights, and Chrome DevTools. In DevTools, open the Performance panel, replay a user scenario, and look for the "Interaction to Next Paint" entry under the "Main" thread. Tools also provide a numeric value in milliseconds and a rating (good, needs improvement, poor) based on thresholds: 300 ms is poor.
04Common mistakes
Marketers and developers often misjudge INP because they focus only on load time or LCP. They also assume that any click will trigger a paint, ignoring cases where the interaction does not produce visual feedback. Another mistake is measuring INP on a synthetic benchmark without real user input, which can give an inaccurate picture of actual responsiveness.
- Confusing INP with LCP or FID.
- Testing only on fast devices and ignoring mobile constraints.
- Assuming all clicks produce a paint without verifying UI updates.
05Limits
INP does not apply when a page has no interactive elements, such as static image galleries. It also does not capture delayed visual changes that happen after the initial paint, like lazy‑loaded content. Because it is based on Chrome’s internal timing, cross‑browser comparisons can be misleading, and it may not reflect user perception on very slow networks where the interaction never reaches the paint stage.
06A worked example
A shopping cart page adds an item to the cart when the user clicks “Add”. The click handler runs a complex validation script that takes 250 ms. The cart updates its count and shows a success toast, which the browser paints after the script finishes. INP for that interaction is 250 ms, falling into the "needs improvement" bucket. The developer moves the validation to a Web Worker, reducing the handler time to 80 ms and the INP to 80 ms, moving the metric into the "good" range.
"Moving the validation off the main thread cut the INP from 250 ms to 80 ms and moved the page from 'needs improvement' to 'good'."
Frequently asked questions
How is Interaction to Next Paint different from Largest Contentful Paint?
No, they measure different aspects of page performance. LCP tracks when the largest element appears, while INP measures the time from user interaction to the next paint after that interaction.
Should I focus on improving Interaction to Next Paint for my e‑commerce site?
Usually, yes, because interactivity affects conversion rates and user satisfaction. Focusing on INP can improve perceived speed and boost sales.
How does Chrome measure Interaction to Next Paint?
It depends on how the browser captures the timing. Chrome starts timing when the user interaction occurs and stops when the next paint frame is rendered, then reports the duration in milliseconds.
Has Interaction to Next Paint been deprecated or is it still relevant?
Yes, it remains relevant and is still tracked in all major performance tools. You’ll see it in Chrome User Metrics, Lighthouse, and PageSpeed Insights.
What problems appear if my site’s Interaction to Next Paint is high?
Yes, high INP can lead to poor user experience and lower search rankings, which you’ll notice as higher bounce rates and reduced conversions. This often results in lost revenue and negative user feedback.
Asked out loud
spoken, not typedThe same term in the words somebody uses speaking to an assistant rather than typing into a box — written from the situation, which is why each one carries the situation it came from.
Usually, the delay is reported in milliseconds and reflects real‑time responsiveness. You’ll see the value in Chrome DevTools after the click.
It depends on how the page is coded, but the browser captures the delay and displays it in performance reports. You’ll see the number in Chrome DevTools or Lighthouse.
Usually, the delay is noticeable when the button takes longer than a few hundred milliseconds to trigger the next paint. You’ll notice lag in user feedback and may see higher abandonment rates.