First Contentful Paint (FCP)
Measures the time when the page first displays anything other than a blank screen.
When a webpage begins to load, the browser shows a blank window. As it downloads the HTML, CSS, JS and other components, the browser is eventually able to draw something. The First Contentful Paint (FCP) metric measures the amount of time that it takes from when the page first starts to load and when it is able to display anything other than a blank screen. The page will very likely continue to load images and other resources after the First Contentful Paint, but at least there is something for the user to start reading.
The scores we use come from a Google Lighthouse report and represent the 28 day average score for the homepage as measured by real users using Chrome. Websites should aim to have a FCP under 1 second, with anything over 3 seconds considered to be poor. A website can optimize for FCP by reducing the size of the DOM, CSS and JS. Also, avoiding multiple page redirects and having a fast server that uses a fast Content Delivery Network (CDN) can make a big difference.
For more information, please read the documentation on Web.dev.