What is cumulative layout shift in plain english?

If you want to see what's shifting on your own page, Chrome DevTools shows it - record a load in the Performance panel and layout shifts appear with the element that moved. Cookie banners and late-loading fonts are two causes people don't think to check. It also counts shifts after load, not just during it, so content that jumps when something expands can hurt too.

It's how much stuff jumps around while the page loads. You go to tap a button, an image or ad loads above it, everything shifts down and you hit the wrong thing. That's layout shift. Google measures it as one of the Core Web Vitals, and under 0.1 counts as good. Usual fixes: set width and height on images and embeds, reserve space for ads, and don't push banners in above the content after it's loaded. Web fonts swapping in late can cause it as well.