INP (Interaction to Next Paint)
Checks Interaction to Next Paint — responsiveness to clicks/taps. Target under 200ms.
What this check measures
We query CrUX for p75 INP. Replaced FID as a Core Web Vital in March 2024. Measures the worst interaction delay across the session.
Why it matters
INP is what users feel when they click and nothing happens for 500ms. Heavy React re-renders, unoptimized event handlers, and synchronous third-party scripts are the usual killers.
How our audit detects it
CrUX p75 INP. Analyze JS bundle size and count blocking scripts for correlation.
Typical findings
- error_outlinep75 INP 450ms — heavy React state update on click.
- error_outlineSync third-party chat script stalls main thread.
- error_outlineNo debounce on input handlers.
How to fix
Profile handlers in DevTools → Performance. Break long tasks with scheduler.yield() or setTimeout. Debounce input events. Defer third-party scripts.
Copy-paste fix prompt for your stack
Lovable · Cursor · Bolt · v0 · Replit · Windsurf · Claude Code · Base44
Frequently asked questions
Does INP measure first click only?expand_more
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Scan my siteRelated checks
LCP (Largest Contentful Paint)
Checks Largest Contentful Paint — how fast the main content appears. Target under 2.5s.
PerformanceCLS (Cumulative Layout Shift)
Checks Cumulative Layout Shift — how much the page jumps during load. Target under 0.1.
PerformanceFCP (First Contentful Paint)
Checks First Contentful Paint — when the first text or image appears. Target under 1.8s.
PerformanceTTFB (Time to First Byte)
Checks Time To First Byte — server response time. Target under 600ms.