First Input Delay: what it is and how to improve page interactivity

First impressions are created in just 7 seconds for human relationships, according to science, but for a website, the time to make an impression is even less; moreover, we will never get “a second chance to make a good first impression,” to paraphrase Oscar Wilde. In short, it is as important as ever to work on perfecting First Input Delay, the element that measures page interactivity and is key to delivering a great on-page experience, as well as being a metric belonging to Google’s Core Web Vitals and a ranking factor on the search engine.

What is the First Input Delay (FID)

First Input Delay (FID) is a user-centric metric that measures the responsiveness of loading and quantifies the experience users experience when attempting to interact with pages that do not respond.

More specifically, First Input Delay is an API that measures how long it takes our site to react after a user has made an interaction with it.

As both the Google guide and the web.dev’s insights explain, FID measures the time elapsed between a user’s first interaction with a page (click on a link, touch of a button, use of a custom Javascript-based control) and the moment when the browser actually responds to the interaction.