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Bytes issue #272, published March 18, 2024, introduced INP as a newly launched Core Web Vital. That was the newsletter’s framing at the time; Google’s current guide, last updated September 2, 2025, identifies INP as a stable Core Web Vital.
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What INP measures
INP measures the latency of qualifying interactions during a page visit: mouse clicks, touchscreen taps, and keyboard presses. It measures from the start of an interaction until the browser can present the next frame. It does not measure every asynchronous task that might continue after that frame.
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Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →An interaction may trigger multiple event handlers. Its latency can include three parts:
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- Input delay: time between the user’s action and the start of the event handlers, often because the browser is busy.
- Processing time: time spent running the interaction’s event handlers.
- Presentation delay: time from the end of handler processing until the next frame is presented.
Scrolling, hovering, and zooming alone are not counted as qualifying interactions. A page may have no INP when its visitors do not perform one of the interactions the metric observes.
What counts as a good INP?
| INP | Assessment |
|---|---|
| 200 milliseconds or less | Good |
| Above 200 through 500 milliseconds | Needs improvement |
| Above 500 milliseconds | Poor |
INP is reported at the 75th percentile of page views, with results segmented for mobile and desktop. In most cases, the metric reflects the slowest qualifying interaction in a visit. For pages with many interactions, the calculation ignores one highest interaction for every 50 interactions, reducing the influence of an isolated outlier.
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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.” The guide attributes the observation that 90% of a user’s time on a page is spent after it loads to Chrome usage data; it does not specify a year for that statistic.
INP versus FID
| Metric | Interactions covered | Latency measured | What it tells you |
|---|---|---|---|
| First Input Delay (FID) | Only the first interaction | Input delay before event handlers begin | Whether the page could begin responding promptly 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 | Whether the page generally responds promptly throughout the visit |
Because INP covers more interactions and more of their latency, a good FID does not establish that every later interaction will feel responsive.
How to find the interaction behind a poor score
Start with field data when it is available: it reflects how people actually use the site. PageSpeed Insights can display Chrome User Experience Report (CrUX) data for qualifying sites. Depending on availability, the field result may describe an individual URL or the broader origin. CrUX can show that responsiveness is a problem, but it may not reveal which interaction caused it.
Real-user monitoring (RUM) can add interaction-level context. After identifying a suspected flow or interaction, reproduce it in a lab and inspect what the browser is doing. Include common user flows and interactions that happen while the page is loading. A lab run only measures the interactions it performs; a clean synthetic result does not prove that every real-user interaction is responsive. Total Blocking Time (TBT) can serve as a proxy in some lab scenarios, but it is not a replacement for INP.
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- Check field results: Open PageSpeed Insights and review the available CrUX data, noting whether it is for the URL or origin and whether it is mobile or desktop.
- Add interaction context: If you have RUM, use it to identify slow interactions and the circumstances around them.
- Reproduce the relevant flow: Test the suspected interaction in a lab, including realistic timing such as input during page loading.
- Find the latency component: Determine whether the delay is before handlers run, inside handler processing, or before the next frame appears.
Ways to improve INP
Choose an intervention only after locating the slow interaction and its bottleneck. The techniques suggested in Bytes #272 are possible tools, not universal fixes.
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Yield to the main thread and break up work
If a long event callback keeps the browser from handling other work, divide the work into smaller tasks and allow the browser to yield between them. The issue points to setTimeout() as one possible way to schedule subsequent work. Moving work later is appropriate only when it preserves the interaction’s behavior and does not leave the user waiting for an essential result.
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Consider a task scheduler
The newsletter names main-thread-scheduling as a cross-browser JavaScript task-scheduler option. Scheduling can help organize work so urgent interaction handling is not blocked, but it will not automatically make expensive work cheaper or solve a delay caused elsewhere.
Defer off-screen rendering where suitable
CSS content-visibility can defer rendering of off-screen content. It may reduce work in pages with substantial content beyond the visible area, but it will not address every INP bottleneck; verify that the slow interaction is affected before adopting it.
Does a better INP guarantee higher Google rankings?
No ranking gain can be promised from an INP score alone. Bytes #272 framed optimization as potentially affecting Google rankings, while the current guide establishes INP as a Core Web Vital and a measure of responsiveness—not a quantified ranking effect. Improving responsiveness has a direct user-facing purpose: making interactions feel faster and more reliable.
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