What is First Input Delay (FID)?
First Input Delay (FID) was a Core Web Vitals metric that Google used to measure a webpage’s responsiveness. The metric measured the duration between the moment a user clicked on a button or link on a page and the moment the page returned feedback indicating the interaction was successful.
The First Input Delay, sometimes called input latency or input delay, is measured in milliseconds. When it was a Core Web Metric, Google recommended that you keep it below 100 milliseconds.
However, the First Input Delay ceased to be a Core Web Metric in March 2024 when it was replaced by the Interaction to Next Paint (INP). Google will end support for the First Input Delay metric on September 9, 2024.