CLS 0.31 -> 0.02 on a magazine layout

CLS 0.31 -> 0.02 on a magazine layout
CLS = Cumulative Layout Shift. A web font swapped in 600ms after paint and reflowed every headline.
— Measured: 0.24 of the 0.31 shift came from the font swap, 0.07 from a late-loading ad slot.
— Preloaded the WOFF2, set font-display: optional, matched fallback metrics with size-adjust.
— Reserved fixed height on the ad container.
p75 CLS: 0.31 | 0.02
Takeaway: 0.29 of layout shift was two elements; both fixed with reserved space, zero redesign.