Guide to Measure and Improve First Input Delay

Last Updated:June 30, 2021

What is the First Input Delay?

First Input Delay is the time between when the user interacts with a page, a clicking on a link or button, and when the browser starts processing the event handler.

In other words , when a user does an action on web pages he has to wait some time to see the response to that action. 

First Input Delay is one of the Core Web Vitals metrics, along with Cumulative Layout Shift (CLS) and Largest Contentful Paint (LCP), which are a subset of Google’s Page Experience ranking signals.

This is used to measure the interactivity of the pages.

You have to measure this metric in real time as you need the user to do action on the web page.

First Input Delay