First Input Delay (FID) vs. Interaction to Next Paint (INP)

As of March 2024, Interaction to Next Paint (INP) will replace First Input Delay (FID) as a new Core Web Vital. INP measures the time between user interaction and when the browser is able to process the event, the time it takes the browser to process the event handlers, and the time it takes the browser to recalculate the layout and paint the pixels to the screen. Unlike FID, which only considers the delay of the first input event, INP measures all interactions throughout a page's lifetime. Optimizing your INP score involves addressing various performance factors such as processing delay, presentational delay, and efficient event handling. Tools like Real User Monitoring (RUM) can be used to regularly collect performance data from actual users for measuring INP.