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Unveiling INP: The Key to Understanding Web Interactivity

This article discusses the Interaction to Next Paint (INP) metric, highlighting its role in assessing web interactivity and responsiveness, and offers strategies for optimization.

Unveiling INP: The Key to Understanding Web Interactivity

The Interaction to Next Paint (INP) metric has emerged as a crucial tool in the web performance toolkit, offering deep insights into the interactivity and responsiveness of web pages. This post delves into the nuances of INP and its significance in optimizing user experience.

What is INP?

INP measures the time between a user’s interaction (like a click or key press) and the browser’s response to that interaction. It’s a Core Web Vital that helps in understanding the real-world interactive experience of users.

Why is INP Important?

INP is critical because it quantifies the user’s experience of a site’s interactivity. A good INP score means a website feels responsive and snappy, directly contributing to user satisfaction and engagement.

How INP Works

INP captures the responsiveness of a website by recording the delay in processing user inputs. It focuses on the worst-case scenarios, highlighting the longest delays users experience while interacting with a page.

Understanding INP Scores

  • Good: An INP of 200 milliseconds or less is considered good, indicating a responsive site.
  • Needs Improvement: INP between 200 and 500 milliseconds needs optimization.
  • Poor: An INP above 500 milliseconds indicates significant responsiveness issues.

Optimizing for INP

Improving INP involves minimizing the time it takes for a web page to respond to user inputs. This can be achieved through various optimization techniques.

Strategies for Enhancing INP

  1. Code Splitting: Reducing JavaScript bundle sizes to ensure quicker processing.
  2. Efficient Loading: Prioritizing the loading of critical resources to improve interaction readiness.
  3. Minimizing Main Thread Work: Reducing long tasks that block the main thread, thereby speeding up response times.

The Impact of INP on User Experience

A good INP score is not just a technical win; it’s a direct contributor to a positive user experience. Faster response times lead to happier users and can significantly reduce bounce rates.

Tools for Measuring INP

Several tools can help measure and analyze INP, including:

  • Chrome User Experience Report (CrUX): Provides real-world INP data collected from actual users.
  • Lighthouse and PageSpeed Insights: Offer lab-based INP measurements and suggestions for improvement.
  • Web Vitals Chrome Extension: Allows developers to measure INP and other Core Web Vitals in real-time.


INP is a pivotal metric for understanding and improving the interactivity of web pages. By focusing on optimizing INP, developers can significantly enhance the user experience, making web pages feel more responsive and engaging. As web technologies evolve, the emphasis on metrics like INP will continue to grow, underscoring the importance of performance in web development.

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