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performanceWeb Platform

Font Display Strategy

MUST

MUST: Use `font-display: swap` to prevent FOIT (invisible text). Preconnect to font CDNs. Preload critical fonts. Match fallback font metrics with `size-adjust` to minimize CLS during font swap.

Prevent invisible text (FOIT) and layout shift from web fonts with proper loading strategies

Bad

Good

Why it matters

Web fonts can cause Flash of Invisible Text (FOIT) affecting LCP, and layout shift when fonts swap. font-display: swap shows fallback text immediately. Metric matching with size-adjust minimizes CLS.

References

Built by Gleb Stroganov, design engineer at Evil Martians.

The rules come from other people's skills and guidelines — Vercel, Rauno Freiberg, @Ibelick, impeccable, Emil Kowalski, Tailwind, RAMS — each one credited on the Sources page. The work here is extraction and wiring: every rule is pulled into one corpus, given a good and a bad example you can operate, a MUST/SHOULD/NEVER rule an agent can paste, and a link back to where it came from.