What you need to know
Web fonts can delay text or change line wrapping after they arrive. That can make a page feel blank or cause content to jump even when the font itself looks good.
How to apply it
Use only the weights and character subsets you need, prefer efficient formats, consider font-display: swap, and choose a fallback font with similar metrics. Preload only a critical font actually used above the fold.
Common mistake to avoid
Do not preload every font file. Unused preload requests compete with images and scripts that may be more important.