Typography

Typography

Type is most of your UI. The system does the hard parts — optical sizes, tracking tables, Dynamic Type — if you use its APIs. This skill covers when to trust the system, how to build hierarchy deliberately, and what custom fonts owe you back.

When This Skill Activates

• Choosing fonts or building a type hierarchy for a screen or app
• Text truncating, cramping, or breaking under larger Dynamic Type sizes
• Adopting a custom/brand font (and keeping accessibility)
• Display typesetting: hero numbers, stats, editorial headlines

Rule 1: text styles first

Predefined styles (Large Title → Caption 2) are weight + size + leading combos with Dynamic Type support built in — and different styles scale differently (body grows more than footnote), which manual font sizes can't replicate.

• Build hierarchy from 2–3 text styles + emphasized variants (bold trait — the actual weight varies per style: some go medium→semibold, others bold→heavy) before reaching for new fonts.
• Semantic colors + text styles together give dark mode, contrast, and Dynamic Type for free.
• macOS supports text styles (without Dynamic Type); design Mac type at 100% — no iOS-style scaling assumptions.

Rule 2: let optical sizes and tracking work

• San Francisco blends Text→Display designs continuously between 17 and 28pt (below: sturdier letterforms, looser tracking for legibility; above: tighter, more refined). System font APIs do this automatically — hardcoded single-cut fonts don't.
• Tracking, not kerning, for letterspacing — tracking is size-specific and lets the OS disable clashing features (ligatures). Override system tracking only in exceptional cases.
• Truncation pressure? Use allowsTightening (default-tightening-for-truncation) instead of manually squeezing — and prefer wrapping to truncating (line limit 0 on labels that matter).
• Line height moves only via leading traits: tight = −2pt, loose = +2pt (±1pt on watchOS); the system adds leading automatically for tall scripts (Arabic, Devanagari).

The Dynamic Type ladder (WWDC24 10074)

12 sizes: 7 default + 5 accessibility (AX1–AX5). .body runs 17pt at default up to 53pt