Max Potential First Input Delay (FID)
How fast your site works during the first user interaction is another essential first impression to keep users on the site. First Input Delay (FID) measures the time from when a user first interacts with your site to the time the browser responds to that. The lower the FID, the more usable the page is.
Timing when the user first interacts with the page is imprecise, but useful. If a user makes their first interaction during a time when the page is loading heavy scripts, this can delay response time and affect user experience.
What is a the first input?
For FID, Google concentrates on user inputs such as clicks, taps and key presses. Actions like scrolling and zooming are considered animation and should be assessed separately since browsers are capable of dealing with them separately.
Why the first input?
Why Google focuses on the first input:
- First impressions are vital to giving users the idea that the site performs quickly and efficiently
- Biggest interactivity issues on sites occur during page load. Improving the sites first user interaction will have greatest effect on overall interactivity.
- Fixes for first input delays are not always related to input delays that occur after the initial page load.
How to fix first input delay
From Google in simple terms: