iOS typography — Dynamic Type, SF, and data-grade numerics

Source: Apple HIG Typography + SwiftUI Font docs, cross-checked across two research passes (June 2026). Apple says: use the built-in text styles, prefer SF, avoid thin weights, support Dynamic Type.

1. The SF family system

Four system typefaces — SwiftUI selects optical sizes automatically:

• SF Pro — default UI sans (.fontDesign(.default)). Auto-switches Text (small) vs Display (large) optical sizes.
• SF Pro Rounded — friendlier; great for large numerics / health-app tone (.fontDesign(.rounded)).
• SF Mono — fixed-width, code/data (.fontDesign(.monospaced)).
• New York — system serif, editorial/reading (.fontDesign(.serif)).

Weights run Ultralight→Black. Don't embed system fonts — use the Font.Design constants. Default iOS text size is 17 pt; minimum 11 pt.

2. Dynamic Type built-in text styles (default "Large" size)

Use these, not hard-coded sizes — they scale with the user's setting, hit larger accessibility sizes, and switch the SF optical variant automatically.