Flash of Unstyled Text (FOUT)

Fonts loading late cause visible text to swap, hurting CLS and polish.

Low priority · Core Web Vitals

What it is

A FOUT/FOUT happens when a web font loads after the text renders in a fallback font, causing a visible swap and layout shift.

Why it matters

Late font swaps shift layout (CLS) and look unprofessional, signalling a lower-quality experience.

How to fix it

Preload critical fonts (font-display: swap or optional), self-host or use a fast font CDN, subset fonts to needed characters, and preload the woff2.

What our AI checks

Our engine flags pages with layout instability likely caused by late fonts and recommends preloading.

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