First Input Delay (FID)

First Input Delay (FID) is the stable Core Web Vital metric for measuring load responsiveness because it quantifies the experience users feel when trying to interact with unresponsive pages—a low FID helps ensure that the page is usable. FID will be replaced by Interaction to Next Paint (INP) as a Core Web Vital in March 2024. To provide a good user experience, pages should have a FID of 100 milliseconds or less.