Font loading
Web fonts add weight and block rendering: poorly loaded, they delay text or make it swap visibly under the reader. The loading strategy determines the trade-off between typographic elegance and layout shift.
In practice
The survival kit: WOFF2 only, subsets limited to needed characters, appropriate font-display, preloading of the headline font, adjusted fallback metrics to neutralize the swap. Two typefaces serve any identity; each additional weight costs milliseconds of first render.