The empirical studies come from data with high variability and gradual decline, rather than hard thresholds, and other studies are based on theoretical predictions. But in general, they suggest that it is worthwhile to keep load times under a few seconds. The Largest Contentful Paint (LCP) measures how long it takes for a page-to-page navigation to be completed for a user. We recommend that sites keep the LCP under 2.5 seconds for 75% of page loads . This recommendation is further informed by Chrome's analysis of the web today and is intended to be feasible for enough sites to achieve in practice. For more details on that analysis, see Defining Core Web Vital metric thresholds .
Cumulative Layout Shift or CLS measures visual stability. Google states that objects and elements should not move around on the page as it is being renderedloaded for the user. Basically, CLS refers to any expected luxembourg mobile database layout changes that occur during the lifecycle of a webpage. We’ve all surely experienced loading a page on our phones, going to press a button, only to have the position of the button move at the last second, and as a result, we clicked on something else and the page had an unexpected layout change. Most web pages have several elements that need to load, and these elements are usually loaded progressively.
This can actually be a good thing: if some content appears early, the user can start moving towards their goal without having to wait for everything to load. However, if the position of an already visible element moves as other elements load, this can negatively impact the user’s experience in two ways . One is that if the element they are looking at suddenly moves, it will take at least a few hundred milliseconds for their eyes to find its new position. If it scrolls out of view, it will take even longer.