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
at AX5 — roughly 3× taller, and layouts must expect that. Escalate in order:
- Text styles —
.font(.title)/preferredFont(forTextStyle:)+ adjusts-for-content-size, line count 0 so text wraps instead of truncating. @ScaledMetricfor the non-text riding alongside (icon frames, spacing); SF Symbols scale viaUIImage.SymbolConfiguration(textStyle:). Prioritize scaling essential content over decoration.- Switch layout axis at accessibility sizes — branch on
dynamicTypeSize.isAccessibilitySizewithAnyLayout(HStackLayout())/AnyLayout(VStackLayout())(UIKit: flip the stack axis onpreferredContentSizeCategory.isAccessibilityCategory); give text the full line width and relaxlineLimit. - Large Content Viewer — only for bars that legitimately can't grow: a tab bar takes under 10% of screen height, and scaled to accessibility sizes it would eat almost a quarter (WWDC24 10074). Scaling is always preferred; the viewer is the fallback, not the fix.
Test at all 12 sizes (Xcode Previews → Variants → Dynamic Type Variants), not just the biggest — mid-range accessibility sizes catch different wrap points.
The San Francisco family — pick by job
| Face | Job |
|---|---|
| SF Pro | The default; UI text everywhere |
| SF Pro Rounded | Friendlier numerals/labels — widgets, health/fitness data |
| SF Compact | watchOS (space-efficient counterpart) |
| SF Mono | Code, tabular alignment |
| New York | Serif — reading experiences, editorial contrast |
| SF Arabic / SF Arabic Rounded | Arabic script with its own optical sizes |
The width axis (Condensed / Regular / Compressed / Expanded):
- Default Regular; every non-Regular choice is a legibility decision — check it.
- Condensed: fit more text comfortably (long headlines wrap one line fewer).
- Compressed: display-only density, not body text.
- Expanded: display typesetting AND small secondary labels (wide + loose tracking).
- Width is a fourth hierarchy lever beside weight, size, color; all widths share identical vertical proportions, so mixing them never misaligns baselines. 2–3 styles are enough — pair one width with contrasting weights, one weight with contrasting widths, or oppose both for maximum display contrast.
Custom fonts: what you owe back
System fonts get Dynamic Type free; a brand font makes you the type engine:
- Scale with
UIFontMetrics(forTextStyle:).scaledFont(for:)+ adjusts-for-content-size, or SwiftUIFont.custom(_:size:relativeTo:); scale layout constants with@ScaledMetric. - Test at the largest accessibility sizes — wrap to multiple lines rather than truncate.
- Verify script coverage for your locales; have a fallback plan for writing systems the brand
font doesn't cover (the system stacks:
system-ui,ui-rounded,ui-serif,ui-monospaceon the web). - Budget for the maintenance: tracking tables, optical sizing, and weight ramps are things SF does that a licensed font usually doesn't.
❌ Anti-patterns: hardcoded point sizes on user-facing text · kerning APIs for tracking jobs ·
custom font without relativeTo: (frozen size) · Compressed body text · truncation where
wrapping was possible.
Output Format
Type review: Element | Current (font/size/style) | Issue (hierarchy/scaling/legibility) | Fix
— check Dynamic Type at XXL + AX sizes before signing off; pairs with the contrast rules in
generators/accessibility-generator.
References
- https://developer.apple.com/videos/play/wwdc2020/10175/ (The details of UI typography)
- https://developer.apple.com/videos/play/wwdc2022/110381/ (The expanded San Francisco family)
- https://developer.apple.com/fonts/ (SF + New York downloads)
- https://developer.apple.com/design/human-interface-guidelines/typography
- Related skills:
design/sf-symbols(symbols align to text styles),foundation/attributed-string(rich text mechanics),generators/accessibility-generator
