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Understanding Interaction to Next Paint (INP): A Comprehensive Guide

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In the world of building websites and apps, there’s a very important term: Interaction to Next Paint (INP). This word helps us understand how fast a website or app feels to someone using it. Knowing about INP helps designers and programmers make interfaces that are smoother and easier to use. In this guide, we’ll explain what INP is, why it’s important, and how to make it better for both web design and app design.

What is Interaction to Next Paint (INP)?

Interaction to Next Paint (INP) is a metric that measures the time it takes for a user interaction to result in a visible change on the screen. It is often used to gauge a responsive website or application. For example, when a user clicks on a button or scrolls down a page, the INP measures the time it takes for the screen to update and reflect the new state.

Significance of INP in Web Design and Development

Interaction to Next Paint (INP)  plays a crucial role in shaping the user experience. A low INP indicates that the website or application responds quickly to user interactions, making it more engaging and user-friendly. On the other hand, a high INP can lead to a sluggish and unresponsive interface, resulting in a poor user experience.

Optimizing INP for Better Performance

There are several strategies that developers and designers can employ to optimize Interaction to Next Paint (INP)  and improve overall performance:

  • Reduce Server Response Time: A fast server response time can significantly reduce the Interaction to Next Paint (INP). Developers should focus on optimizing server-side code and using efficient hosting solutions.
  • Minimize Render-Blocking Resources: Render-blocking resources such as CSS and JavaScript files can delay the rendering of a page, increasing the INP. To minimize this, developers should use asynchronous loading techniques and defer the loading of non-essential resources.
  • Optimize Images and Videos: Large images and videos can increase the load time of a page, leading to a higher INP. Developers should optimize media files for the web and use lazy loading techniques to defer the loading of off-screen images and video
  • Use Browser Caching: Caching can help reduce the INP by storing frequently accessed resources locally on the user’s device. Developers should leverage browser caching to reduce the load time of subsequent visits to the website or application.
  • Prioritize Critical Rendering Path: The critical rendering path refers to the sequence of steps browsers take to render a web page. Developers should prioritize the loading of critical resources such as CSS and JavaScript files to reduce the INP.

How to Measure INP?

Measuring INP requires the use of performance monitoring tools that can track user interactions and screen updates. One popular tool for measuring Interaction with Next Paint (INP)  is Google’s Web Vitals, which provides a comprehensive set of metrics for assessing the performance of web pages.

To measure INP using Web Vitals, developers can use the following steps:

  • Set Up Performance Monitoring: Install Google Analytics on your website and enable the Core Web Vitals report to start monitoring performance metrics, including INP.
  • Analyze Performance Data: Use the Core Web Vitals report in Google Analytics to track Interaction to Next Paint (INP) and other performance metrics over time. Identify any issues that may be affecting the INP and take corrective action.
  • Optimize for Better Performance: Based on the performance data, optimize your web design and development or application to improve the Interaction with Next Paint (INP). This may involve implementing the optimization strategies mentioned earlier, such as reducing server response time and optimizing images and video

Common Challenges and Solutions for Interaction To Next Paint Optimization

  • Heavy JavaScript: Excessive use of JavaScript can increase the time it takes for a page to respond to user interactions. To mitigate this, developers should minimize the use of unnecessary JavaScript code and prioritize critical scripts for faster loading.
  • Render-Blocking CSS: CSS files that are render-blocking can delay the rendering of a page, leading to a higher INP. Developers should optimize CSS delivery by using techniques such as minification and asynchronous loading.
  • Large DOM Size: A large Document Object Model (DOM) can slow down rendering and increase the INP. Developers should strive to keep the DOM size as small as possible by avoiding unnecessary elements and using efficient coding practices.
  • Third-Party Scripts: Third-party scripts such as ads and analytics trackers can significantly impact INP. Developers should carefully evaluate the necessity of third-party scripts and consider loading them asynchronously to minimize their impact on performance.
  • Network Latency: Slow network connections can increase the time it takes for a page to respond to user interactions. Developers should optimize content delivery by using content delivery networks (CDNs) and compressing files to reduce latency.

Best Practices for Interaction To Next Paint Optimization

  • Prioritize Above-the-Fold Content: Load critical content above the fold first to provide users with a fast initial rendering experience.
  • Lazy Load Non-Critical Content: Defer the loading of non-critical content such as images and videos until they are needed, reducing the initial load time and improving the interaction To Next Paint.
  • Optimize Font Loading: Use font-display: swap; in your CSS to ensure that text is displayed using system fonts while web fonts are loading, reducing the perceived loading time.
  • Reduce Server Response Time: Optimize server-side code and use caching mechanisms to reduce the time it takes for the server to respond to requests.
  • Monitor and Analyze Performance: Continuously monitor and analyze performance metrics, including INP, to identify areas for improvement and implement optimization strategies accordingly.


In conclusion, Interaction with Next Paint (INP) is a critical metric in web design and development that can significantly impact the user experience. By understanding the importance of Interaction with Next Paint (INP) and implementing optimization strategies, developers and designers can create more efficient and user-friendly interfaces.


  1. What is Interaction to Next Paint (INP) and why is it important in web design and development?
    1. Interaction to Next Paint (INP) measures the time it takes for a user interaction to result in a visible change on the screen. It’s important because it reflects the responsiveness of a website or application, which is crucial for a positive user experience.
  2. How does INP affect the user experience of a website or application?
    1. A low INP means quicker screen updates, leading to a more responsive and engaging user experience. Conversely, a high INP can result in a sluggish interface, impacting user satisfaction.
  3. What are some common challenges faced in optimizing INP?
    1. Heavy JavaScript, render-blocking CSS, large DOM size, third-party scripts, and network latency are common challenges that can affect Interaction to Next Paint (INP)  optimization.
  4. How can developers reduce server response time to improve INP?
    1. Developers can reduce server response time by optimizing server-side code, using efficient hosting solutions, and leveraging caching mechanisms.
  5. What strategies can be used to minimize render-blocking resources and improve INP?
    1. Developers can use asynchronous loading techniques, defer non-essential resource loading, and prioritize critical scripts to minimize render-blocking resources.
  6. How does optimizing images and videos help in reducing INP?
    1. Optimizing images and videos reduces their file size, resulting in faster loading times and lower INP.
  7. What role does browser caching play in optimizing INP?
    1. Browser caching stores frequently accessed resources locally on the user’s device, reducing the need for repeated downloads and improving INP.
  8. How can developers prioritize critical rendering paths to improve INP?
    1. Developers can prioritize loading critical resources such as CSS and JavaScript files to ensure faster rendering and lower INP.
  9. What tools can be used to measure INP and track performance metrics?
    1. Tools like Google’s Web Vitals provide metrics for measuring INP and other performance metrics, helping developers track and optimize performance.
  10. What are some best practices for optimizing INP in web design and development?
    1. Best practices include prioritizing above-the-fold content, lazy loading non-critical content, optimizing font loading, reducing server response time, and continuously monitoring and analyzing performance metrics.

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