What is it?
This test will check the Cumulative Layout Shift (CLS) score of the analyzed webpage. CLS is a Core Web Vitals metric calculated by summing all layout shifts that aren't caused by user interaction. Basically, whenever a page loads, certain page elements unexpectedly shift, affecting the way users interact with the webpage. A website with a low CLS has a stable page display, which does not shift elements around and ensures a steady, predictable loading of all website content. To provide a good user experience, sites should strive to have a CLS score of 0.1 or less.