Confession Time: I don’t care about the Core Web Vitals update. However. I do care about one element of the update: Cumulative Layout Shift. This is when stuff shifts around on a web page. There’s more to it than that- and that’s what this article is about. This post is an attempt to get the most comprehensive view of Cumulative Layout Shift: what it is, what it measures, how it measures, how you can see it, and how you can fix it.