INP (Interaction to Next Paint) is a performance metric engineered to quantify the time it takes for a web page to visibly respond to a user interaction (such as clicks or taps).
Google’s Chrome Team announced in May 2023 that INP is scheduled to officially replace FID (First Input Delay) in 2024. Interaction to Next Paint (INP) is currently being positioned as the successor to First Input Delay (FID) as a primary Core Web Vitals metric. INP is expected to provide more accurate results and a better reflection of real-world performance, making it the preferred metric moving forward for assessing a webpage’s responsiveness after user engagement.
How is INP Measured?
A low INP score indicates minimal latency between a user interaction and the page’s response, whereas a high INP score suggests increased delay between the interaction and the visual feedback. According to Google’s stated guidelines:
An INP score at or below 200 milliseconds signifies that your page has good responsiveness.
An INP score above 200 milliseconds but at or below 500 milliseconds suggests that your page’s responsiveness needs improvement.
An INP score above 500 milliseconds indicates that your page has poor responsiveness.
Why INP is Superior to FID
The central motivation for implementing the INP metric was to capture the full, end-to-end latency of an event. Since First Input Delay only measured a fraction of the total delay between the moment a user clicks and the browser finishes responding, the reading provided was, to put it simply, often incomplete or inaccurate.
The Google Chrome teams intend for INP to serve as a complete measure of a web page’s reaction time following a user interaction.