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Interaction to Next Paint (INP): A Practical Guide to Faster-Feeling Websites
What INP measures, why it matters for SEO and conversion, and the practical fixes that make websites and web apps respond instantly.
Since 2024, Interaction to Next Paint (INP) has been one of Google's Core Web Vitals, replacing First Input Delay. INP measures how quickly a page responds visually after a user clicks, taps or types — across the whole visit, not just the first interaction.
Why it matters
A page that loads fast but freezes when you tap "Add to cart" feels broken. Poor INP hurts conversion and is a page experience signal for search.
The thresholds
- Good: 200 milliseconds or less
- Needs improvement: 200–500 milliseconds
- Poor: over 500 milliseconds
Measured at the 75th percentile of real user visits.
What causes poor INP
- Long JavaScript tasks blocking the main thread
- Heavy event handlers doing too much work synchronously
- Large DOM updates and expensive re-renders
- Third-party scripts — chat widgets, tag managers, ads and trackers
- Hydration of large client-side frameworks
Practical fixes
- Ship less JavaScript. Server-render content and only hydrate interactive parts.
- Break up long tasks. Yield to the browser between chunks of work.
- Give instant visual feedback. Update the button state first, then do the heavy work.
- Debounce expensive input handlers such as search-as-you-type.
- Audit third-party scripts. Remove, defer or load them after interaction.
- Reduce DOM size and avoid layout thrashing.
- Virtualise long lists in dashboards and feeds.
How to measure
- Field data: Chrome UX Report and Search Console for real-user INP
- Real user monitoring: collect INP from your own visitors to find the slow interactions
- Lab tools: Chrome DevTools performance panel to diagnose specific interactions
Quick wins we see often
Removing unused tag manager tags, lazy-loading chat widgets and replacing heavy carousels can transform INP on marketing sites. For web apps, splitting large components and memoising expensive renders usually helps most.
Our web application development and React teams build with performance budgets from the first sprint.
