Interaction to Next Paint [INP]

Interaction to Next Paint (INP) is a Core Web Vitals metric that measures the overall responsiveness of a web page to user interactions throughout the entire time a user is on the page. It captures how quickly a page visually responds when a user interacts with it (such as clicking a button, tapping a link, or selecting from a dropdown) and reflects the delay between that interaction and the next time the page updates its visual display in response.

INP replaced First Input Delay (FID) as an official Core Web Vitals metric in March 2024, following an extended period during which it was available as an experimental metric. The change was made because INP provides a more comprehensive and representative picture of real-world page responsiveness than FID, which only measured the delay on the very first interaction a user made with a page.

How INP is Measured

INP observes all qualifying interactions — clicks, taps, and keyboard inputs — that occur during a user’s visit to a page. For each interaction, it measures the time from when the user initiates the input to when the browser is next able to paint a visual update in response. The INP score for the page is then determined by the longest interaction delay observed during the session, with some allowance made for outliers on pages with a very high number of interactions.

INP thresholds as defined by Google:

• Good — 200 milliseconds or under
• Needs Improvement — between 200 and 500 milliseconds
• Poor — above 500 milliseconds

Common Causes of Poor INP

• Long JavaScript tasks — scripts that run for extended periods block the browser’s main thread, preventing it from responding to user interactions promptly
• Excessive DOM size — a very large Document Object Model can slow down the browser’s ability to calculate and render updates in response to interactions
• Heavy third-party scripts — analytics tools, advertising scripts, chat widgets, and other third-party code can consume main thread resources and delay interaction responses
• Render-blocking resources — CSS or JavaScript that prevents the browser from painting updates quickly in response to user input
• Inefficient event handlers — poorly optimised code triggered by user interactions that performs too much work before allowing the browser to update the visual display

A poor INP score indicates that a page feels sluggish and unresponsive to users, which negatively impacts the overall experience and can contribute to higher bounce rates and lower engagement. While page experience signals are not the dominant ranking factor, failing to meet the Core Web Vitals thresholds can put a site at a disadvantage relative to competitors who do meet them. INP performance data is available through the Chrome User Experience Report (CrUX), Google Search Console’s Core Web Vitals report, and tools such as PageSpeed Insights and Lighthouse, making it straightforward to identify pages that need attention and diagnose the underlying causes of poor responsiveness.