LCP evaluates page loading speed. It tracks how long it takes for content, images, video poster images and background images to load into the user viewport. The website should be designed in such a way that the web pages load in less than 2.5 seconds.
FID evaluates user interaction with the website. It measures the time it takes to respond to user input on a website, such as clicking a button or a link. The website's goal is to deliver user interaction with an FID of less than 100 milliseconds.
CLS evaluates the user experience of the website. It monitors the website content, such as text, buttons, and images, which flutter when the viewer reads the information on the website. The website should ensure that the CLS is kept at a range of 0.1 or less.
FCP is a user-centric metric for measuring perceived load speed. FCP tracks how long it takes a user's browser to render the document object model such as images, non-white canvas elements, and SVGs.