What is CLS (Cumulative Layout Shift)?
A measurement of how much elements on the page move around after the initial paint. Lower is better; a passing score is under 0.1.
Also known as: Cumulative Layout Shift, layout jumping
Cumulative Layout Shift quantifies how visually stable a page is as it loads. Every time an element shifts position after the first paint — an image loading and pushing text down, a font swapping size, a late-arriving ad — that contributes to the CLS score.
A passing CLS is under 0.1. Most sites fail because they don't reserve space for images (no width + height attributes), they use web fonts without size-adjust, and they inject above-the-fold ads or chat widgets without holding space.
Fixing CLS is mostly mechanical: set explicit width/height on every image, use font-display: swap with size-adjust, and reserve fixed dimensions for anything injected by JavaScript. Nexora ships sites with CLS scores typically under 0.02 because we handle these patterns at build time.
High CLS makes a site feel cheap and unstable. It also actively triggers users to mis-tap, leading to higher bounce rates and lower conversions.