Understanding Interaction to Next Paint (INP)


In the world of web development, providing a smooth and responsive user experience is crucial for the success of a website or web application. Users expect pages to respond quickly to their actions, and delays can lead to frustration and a negative impression of the site. To measure and improve responsiveness, developers rely on metrics such as Interaction to Next Paint (INP). In this article, we will explore the concept of INP, its significance in evaluating web page responsiveness, how it is calculated, and its differentiation from other metrics.

Understanding INP:

Interaction to Next Paint (INP) is a metric that focuses on the time between a user initiating an interaction with a web page and the subsequent frame being painted by the browser. It measures the delay between user input and the visual feedback displayed on the screen. By minimizing this delay, developers can ensure that users perceive the page as responsive and actively responding to their actions.

Importance of Visual Feedback:

Visual feedback is a crucial aspect of user interactions with web pages. It provides users with confirmation that their actions have been registered and the page is responding accordingly. For example, when a user adds an item to an online shopping cart, immediate visual feedback assures them that the action was successful. Delayed or absent visual feedback can create a perception of unresponsiveness, leading to user frustration and potential abandonment of the site.

Calculating INP:

INP is calculated by monitoring all user interactions on a web page. The metric captures the time between the user’s interaction and the subsequent frame being painted. For most websites, the interaction with the longest delay is reported as the INP value. However, to account for occasional delays that can occur on pages with numerous interactions, one highest interaction is ignored for every 50 interactions. This adjustment helps provide a more accurate representation of the page’s responsiveness. The reported INP value corresponds to the 75th percentile of all page loads, reducing the impact of outliers on the metric.

Differentiating INP from other metrics:

INP differs from metrics such as First Input Delay (FID) in its scope. While FID measures the delay between the user’s first interaction and the browser’s response during page loading, INP captures the overall responsiveness of a web page to all user interactions. INP offers a comprehensive assessment of a page’s responsiveness beyond just the first interaction, making it a more reliable indicator of the user experience.

Scenarios without INP value:

There are certain scenarios where an INP value may not be reported. This can happen if the user does not engage in any mouse clicks, touchscreen taps, or keypress events on the page. Additionally, interactions such as scrolling or hovering are not considered when calculating INP. Moreover, if a page is accessed by bots or search crawlers that do not interact with the page, no INP value will be generated.


Assessing and optimizing the responsiveness of web pages is vital for delivering a seamless user experience. The Interaction to Next Paint (INP) metric provides valuable insights into how quickly a page responds to user interactions and presents visual feedback. By aiming for a low INP value, developers can ensure good responsiveness and enhance user satisfaction. Regular monitoring and improvement of INP can contribute to increased engagement, improved user experience, and the success of websites and web applications in today’s competitive digital landscape.

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