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Interaction to Next Paint (INP) measures how quickly a page responds to clicks, taps, and keyboard input across a visit. A good INP is 200 milliseconds or less; above 500 milliseconds is poor. Bytes issue #272 introduced the metric in March 2024, when it replaced First Input Delay (FID) as a Core Web Vital. INP remains a Core Web Vital; Google’s current guide was last updated September 2, 2025.
What INP measures
INP tracks the time from a qualifying user interaction until the browser can present the next frame. A single interaction can trigger several event handlers. Its latency includes three parts: the delay before the handlers begin, the time spent processing them, and the delay before the next frame appears. INP is not a measure of every asynchronous task that might continue after that frame.
Qualifying interactions include mouse clicks, touchscreen taps, and keyboard presses. Scrolling, hovering, or zooming by themselves do not count. A page may have no INP value if visitors did not perform a qualifying interaction.
The metric is intended to reflect the page’s responsiveness throughout a visit, rather than just what happens at page load. Chrome usage data, as reported in the official web.dev INP guide, indicates that 90% of a user’s time on a page is spent after it loads.
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What counts as a good INP?
| INP | Assessment |
|---|---|
| 200 milliseconds or less | Good |
| Above 200 milliseconds through 500 milliseconds | Needs improvement |
| Above 500 milliseconds | Poor |
These thresholds apply to the 75th percentile of page views, assessed separately for mobile and desktop. In most cases, INP reflects the slowest interaction recorded during a visit. On pages with many interactions, the calculation ignores one highest-latency interaction for every 50 interactions, so an isolated outlier does not dominate the result.
How INP differs from FID
| Metric | Interactions covered | What the latency includes | What it tells you |
|---|---|---|---|
| First Input Delay (FID) | Only the first interaction | Input delay before event handlers run | How quickly the page began responding to the first input |
| Interaction to Next Paint (INP) | Qualifying interactions across the page visit | Input delay, handler processing, and presentation delay until the next frame | How responsive the page was across user interactions |
FID could miss a page that handled the first input promptly but lagged on later actions. INP covers that broader experience. As the web.dev guide puts it, “A low INP means the page was consistently able to respond quickly to all—or the vast majority of user interactions.”
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How to find the interaction behind a poor INP
Start with field data, which reflects what real visitors experienced. Then use interaction-level context and controlled reproduction to locate the cause. Field data can show that responsiveness is a problem without identifying the code responsible.
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Enter the site or page URL in PageSpeed Insights and look for Chrome User Experience Report (CrUX) field data. Depending on what CrUX has available, the result may describe the individual URL or the site’s origin. If field data is unavailable, that does not establish that every interaction is responsive; it means the report cannot provide a field result for that page or origin.
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2. Add interaction context with RUM
Real User Monitoring (RUM) can add detail about the interactions and conditions associated with slow field experiences. This helps narrow down which user flow, page state, or interaction deserves investigation. CrUX and RUM serve different purposes: CrUX reports field outcomes, while RUM can provide more context about what users were doing.
3. Reproduce the suspected interaction in a lab
Use browser performance tools or an appropriate testing setup to replay common user flows and inspect the slow interaction. Include interactions made while the page is still loading if that reflects how visitors use it. Lab findings depend on which interactions you perform: a clean run does not prove that all real-world interactions respond quickly.
Total Blocking Time (TBT) can serve as a proxy in some lab scenarios, but it is not a substitute for INP. Use it as one diagnostic clue, not as proof of field responsiveness.
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How to improve a slow interaction
Choose an intervention only after identifying whether the delay comes from waiting to run handlers, work inside the handlers, or the browser’s delay before presenting the next frame. The techniques below were suggested in Bytes #272; they are options to consider, not guaranteed fixes.
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Yield to the main thread and break up long work
If an event callback performs too much work at once, divide that work into smaller tasks so the browser has opportunities to respond between them. The issue gives setTimeout() as one way to yield. This is useful only when the callback’s processing is the bottleneck; moving work without addressing the actual delay may not improve the interaction.
Consider a task scheduler
Bytes points to main-thread-scheduling as a cross-browser JavaScript task-scheduling option. A scheduler can help structure when work runs, but it does not remove expensive work by itself. First determine which work can be deferred or split without changing the interaction’s expected result.
Defer off-screen rendering where appropriate
The CSS property content-visibility can defer rendering of off-screen content. It may help when rendering work contributes to the delay, but it is not a general fix for slow event handlers or input delay. Evaluate it against the page’s layout, accessibility, and user-visible behavior.
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What INP can—and cannot—tell you
INP is a measure of user-visible responsiveness, not a direct guarantee of search ranking gains. The March 2024 Bytes issue framed INP optimization in relation to Google rankings, while the current metric guidance establishes its Core Web Vital status and how responsiveness is measured; it does not quantify a ranking effect. Treat a poor score first as evidence of friction for users, and investigate the interactions causing it.
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