Cumulative Layout Shift

The Cumulative Layout Shift (CLS) indicates whether there are unexpected shifts of visible content, such as banners, images, videos or H1 titles. When the page speed of a page is too low, certain elements on a page may jump, which is detrimental to the user experience. 

A CLS score lower than 0.1 means that few or no elements on a page are skipped. 

You can improve the CLS score in different ways. For example, you can reduce the size of heavy files such as images or videos so that they load faster. In addition, certain files that do not need to be above the fold can be placed lower in Javascript. Banners and other advertisements, for example, can be placed at the bottom of the page, so that the content does not shift during loading. 

CLS is one part of the three Google Core Web Vitals. The other two parts are First Input Delay and Largest Contentful Paint.