What is INP (Interaction to Next Paint)?
INP (Interaction to Next Paint) is a Core Web Vitals metric that measures page responsiveness by evaluating the time between user interactions—like clicks, taps, or key presses—and when the browser visually responds to those actions. Google uses INP as a ranking factor starting March 2024, replacing First Input Delay, making interaction responsiveness critical for both user experience and search performance.
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What You Need to Know about INP (Interaction to Next Paint)
Interaction Delay Components
INP encompasses three phases: input delay before the browser processes the interaction, processing time for event handlers to execute, and presentation delay before visual updates appear. Optimizing all three phases is necessary to achieve good INP scores under 200 milliseconds.
User Experience Impact
Slow INP creates frustrating experiences where buttons don’t respond, forms feel laggy, or navigation clicks require multiple attempts. These responsiveness problems increase bounce rates and reduce engagement, harming both conversion rates and behavioral signals that influence rankings.
JavaScript Execution Blocking
Heavy JavaScript processing blocks the main thread, preventing the browser from responding to user interactions quickly. Long-running scripts, unoptimized third-party code, and excessive DOM manipulation are primary causes of poor INP performance.
Measurement Across Page Lifespan
Unlike First Input Delay which only measured the first interaction, INP evaluates responsiveness throughout the entire page visit. This comprehensive measurement means sites must maintain performance even after initial load, preventing degradation as users interact with content.
Good Score Thresholds
INP scores under 200 milliseconds are considered good, 200-500 milliseconds need improvement, and above 500 milliseconds are poor. These thresholds apply to the 75th percentile of page visits, meaning most users should experience responsive interactions for passing scores.
Optimization Strategies
Reduce JavaScript execution time by code splitting, deferring non-critical scripts, and minimizing main thread work. Break long tasks into smaller chunks, use web workers for heavy processing, and optimize event handlers to execute quickly without blocking user interactions.
Frequently Asked Questions about INP (Interaction to Next Paint)
1. Why did Google replace FID with INP?
FID only measured the first interaction and ignored processing time, missing most responsiveness problems users actually experience. INP provides more comprehensive coverage of interaction responsiveness throughout page visits, better reflecting real user experience quality.
2. How do you test INP performance?
Use Chrome DevTools to identify long tasks blocking interactions, PageSpeed Insights for field data from real users, and Web Vitals extension for real-time monitoring. Test on mid-range mobile devices where performance problems are most apparent.
3. What causes poor INP scores?
Heavy JavaScript frameworks, unoptimized third-party scripts, long-running event handlers, excessive DOM updates, and render-blocking resources all contribute to slow interaction responses. Priority improvements target the heaviest blocking tasks identified through performance profiling.
4. Does INP affect mobile rankings more than desktop?
Google uses mobile page performance for mobile-first indexing, making mobile INP particularly important. However, poor responsiveness on any device type signals quality problems, so optimization should address both mobile and desktop experiences for comprehensive search performance.
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