INP
Interaction to Next Paint: how quickly a page responds when people interact with it.
What INP measures
Interaction to Next Paint measures how quickly a page responds visually when someone taps, clicks or types. It looks at interactions throughout the visit and reports one of the slowest. A good INP is 200 milliseconds or less, according to web.dev's INP guidance. INP became a Core Web Vital in March 2024, replacing First Input Delay.
How to measure it
INP needs real interactions to measure, so field data is best. Search Console's Core Web Vitals report and PageSpeed Insights show INP where Chrome has enough data. Try your own key tasks on an older phone, such as opening the menu, using filters and filling in the contact form, and note anything that hesitates.
Common causes of a poor result
- Loading every script on every page "just in case".
- Adding more tracking tools than you actually use.
- Testing only on a new, fast phone.
- Assuming INP is a developer-only problem. Plugin and widget choices matter most on small sites.
What a fix looks like
A gym's timetable page lets people filter classes by day. Each tap freezes the page for a moment while a large script recalculates everything. The developer simplifies the filter and delays loading the chat widget until it's needed, and the page feels instant again.
Why speed and stability matter
Poor INP feels like a broken site: a menu button that doesn't open straight away, a form that lags when you type or a basket that freezes. Visitors don't know the cause. They just leave. Heavy JavaScript from page builders, chat widgets and tracking scripts is the usual culprit.
Other speed and experience terms
- Core Web Vitals: Google user-experience metrics: LCP, INP and CLS.
- UX and SEO: Overlap where usability, speed and clarity support search performance.
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