On the web, a good first impression can make the difference between someone becoming a loyal user and them leaving and never coming back. One of the key ways a site shapes our first impression is what happens when we first try to interact with it.

Is it fast and responsive? Is it slow and sluggish? Does it not respond at all (and make us think it’s broken)?

To help quantify this, we’ve introduced a new performance metric called First Input Delay. To quote from my article on developers.google.com:

First Input Delay (FID) measures the time from when a user first interacts with your site (i.e. when they click a link, tap on a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to respond to that interaction.

We’ve also released a small JavaScript library so you can measure this metric yourself and better understand your user’s first impressions.

We’d love for you to give this metric a try and let us know what you think!