How do I fix layout shift (CLS) on my Shopify store?

CLS happens when elements load without reserved space and push content around. The usual causes on Shopify: images and embeds without set dimensions, web fonts swapping in and reflowing text, and app banners/popups injecting content after load. Each one shoves the layout.

Fixes: always set width/height (or aspect-ratio) on images and iframes so the browser reserves the space, use font-display so text doesn't reflow badly, and give announcement bars or injected widgets fixed space. Aim for CLS under 0.1 — once elements stop resizing late, it drops fast.