Interaction to Next Paint (INP) is a new Core Web Vital metric that measures a webpage’s responsiveness to user interactions. It focuses on the time between when a user initiates an interaction (such as clicking, tapping, or keyboard input) and when the next frame is painted with visual feedback. Good responsiveness is crucial in providing users with a smooth and interactive experience.
INP assesses the latency of all click, tap, and keyboard interactions throughout a user’s visit to a page. It calculates the longest interaction observed, ignoring outliers, and reports the 75th percentile value across page views. This helps capture the typical responsiveness experienced by users. An INP below or at 200 milliseconds indicates good responsiveness, while values above 200 milliseconds and below or at 500 milliseconds suggest room for improvement. INP values above 500 milliseconds indicate poor responsiveness.
INP measures the delay between initiating an interaction and presenting visual feedback, disregarding factors like network fetches or asynchronous updates. It only considers specific interaction types such as mouse clicks, touchscreen taps, and keyboard presses, while excluding hover and scrolling events.
INP differs from First Input Delay (FID), which focuses solely on the first interaction and its input delay during page loading. INP provides a comprehensive assessment of overall responsiveness by sampling all interactions, making it a more reliable indicator than FID.
Measuring INP can be done in the field using Real User Monitoring (RUM) tools that gather data from actual users. The Chrome User Experience Report (CrUX) is one such tool that provides INP data. In the lab, slow interactions can be reproduced and optimized using strategies like following common user flows and testing interactions during the page load phase.
To improve INP, it’s important to identify and optimize slow interactions. Analyzing field data and using lab testing can help identify the specific interactions causing delays. Guides and resources are available to assist in diagnosing and optimizing slow interactions for better overall responsiveness.
