By Magnetic Clouds Engineering
Interaction to Next Paint (INP) measures how quickly a page responds to every click, tap and key press — not just the first one. It is now the Core Web Vital we see failing most often in audits.
Why it is hard to fix
There is rarely one big culprit. INP suffers from many small costs: third-party scripts, heavy hydration, expensive re-renders and layout thrashing.
The five steps
- Measure real users first. Lab tests miss the slower phones your customers actually use, so we add real-user monitoring with attribution.
- Break up long tasks. Anything over 50 ms blocks the main thread; we yield to the browser and move heavy work into web workers.
- Ship less JavaScript. React Server Components keep most of the interface on the server.
- Tame third parties. Tag managers, chat widgets and testing tools load on interaction or when idle — never on the critical path.
- Render less. Audit context providers and virtualise long lists.
Across recent performance engagements, median INP fell from around 412 ms to 96 ms and conversion rates rose by an average of 11%.
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