Guide · Web performance
Interaction to Next Paint: INP Explained for Site Owners
Interaction to next paint (INP) is the Core Web Vital that scores how quickly a page responds when people click, tap or type. A good INP is 200 milliseconds or less. This guide covers what it measures, how it replaced FID, what slows it down and how to check your own site.
What INP measures
Interaction to next paint (INP) is a score for how fast a web page reacts when someone uses it. It looks at every click, tap and key press during a visit. For each one, it times the wait from the moment the person acts to the moment the next frame shows on screen.
That wait has three parts. First comes input delay, the time before the page starts to handle the action. Then the page runs its code for that action. Last, the browser needs time to draw the result.
Scrolling, hovering and zooming do not count. A key press on a form field does. So does a tap on a menu button or an "add to cart" button.
The good and poor scores
INP is measured in milliseconds (ms). Google judges it at the 75th percentile of real page visits, split by mobile and desktop. That means three in four visits should score at or better than the number you report.
INP score Rating 200 ms or less Good Over 200 ms, up to 500 ms Needs improvement Over 500 ms Poor For scale, 200 ms is one fifth of a second. A page above 500 ms feels stuck. People click again, because nothing seems to happen.
The final number is usually the slowest interaction on the page. On busy pages with many actions, one very slow one is ignored for every 50 interactions. This keeps a single odd hiccup from ruling the score.
How INP replaced FID
INP is the newer of two speed-of-response scores. The older one was First Input Delay (FID). FID only timed the wait before the page began handling the very first action. It ignored the code run time and the drawing time. It also ignored every action after the first.
Chrome introduced INP as an experimental metric in May 2022. It became a pending metric in 2023. On 12 March 2024, INP became a Core Web Vital and replaced FID. Core Web Vitals are the set of page experience scores that Google asks site owners to track.
Google said at the time that FID would be removed from Search Console on that date. Other tools, such as PageSpeed Insights and the Chrome User Experience Report, kept FID for a six month wind-down.
Sources: web.dev, INP becomes a Core Web Vital on March 12; web.dev, Interaction to Next Paint (INP)
What makes clicks slow
Most slow responses come from the main thread being busy. The main thread is the single lane where the browser runs page code and handles your clicks. If it is busy with a long job, your tap has to wait in line.
- Long tasks. Big chunks of script can lock the lane for a long stretch, and your tap has to wait.
- Slow event handlers. The code that runs after a click may do too much before it lets the page draw.
- Large pages. A big, complex page structure (the DOM) takes longer to update after each action.
- Heavy layout and style work. Complex styling rules and layout changes make the browser spend longer before it can paint.
- Pages built mostly in the browser. When a site draws most of its HTML with JavaScript on the visitor's device, interaction work can pile up.
Google's own advice is to find the slow interaction first and only then pick a fix. It splits fixes into three groups: shorter long tasks, less input delay, and less rendering work.
Sources: web.dev, INP becomes a Core Web Vital on March 12; web.dev, Interaction to Next Paint (INP)
How to check your own site
Start with field data, which comes from real visitors. PageSpeed Insights shows this when enough data exists, using the Chrome User Experience Report. Some sites will not appear in these tools if they have too little traffic.
Field data tells you whether you have a problem. It does not tell you which button is slow. For that, test in the lab. Open the page in Chrome, click through the main actions yourself, and watch for any that pause.
Here is a short list a site owner can use today:
- Check INP for your key pages in PageSpeed Insights.
- Note any page rated needs improvement or poor.
- List the third-party scripts on that page and ask which ones you still need.
- Ask your developer to find the slowest click and time its three parts.
- Re-check after changes, since field data comes from real visits and does not change the moment you fix something.
A page may also show no INP score. That happens if no one clicked, tapped or typed during the visits measured.
Sources: web.dev, Interaction to Next Paint (INP); web.dev, INP becomes a Core Web Vital on March 12
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