Swiftui Design Principles

by arjitj2791d22d73f844167a3872530e3941185b730d8beMIT30 starsListed Oct 9, 2026Updated Oct 9, 2026Repository updated 6 months ago

Design principles for building polished, native-feeling SwiftUI apps and widgets. Use this skill when creating or modifying SwiftUI views, iOS widgets (WidgetKit), or any native Apple UI. Ensures proper spacing, typography, colors, and widget implementations that look and feel like quality apps rather than AI-generated slop.

Instructions onlyDesign & CreativeSoftware Development
AI-generated overview

Guidance for building polished, native-feeling SwiftUI app and WidgetKit interfaces.

What it does
This skill provides a set of design principles for SwiftUI and WidgetKit interfaces, covering spacing grids, typography scales, semantic colors, component sizing, grouped cards, navigation, widgets, interactive elements, and editor state management. It contrasts discouraged patterns with preferred ones through annotated code examples and ends with a shipping checklist. It produces written guidance rather than generated files or code artifacts.
When to use it
Use it when creating or modifying SwiftUI views, iOS widgets, lock screen widgets, or other native Apple UI. It is intended to keep spacing, typography, color, and widget implementation consistent with production-quality apps.
Requirements
No scripts or tools are required; it is an instructions-only document. It assumes familiarity with SwiftUI and WidgetKit APIs.

This skill encodes design principles derived from comparing polished, production-quality SwiftUI apps against poorly-built ones. The patterns here represent what separates an app that feels "right" from one where the margins, spacing, and text sizes just look "off."

Apply these principles whenever building or modifying SwiftUI interfaces, WidgetKit widgets, or any native Apple UI.

Core Philosophy

Restraint over decoration. Every pixel must earn its place. A polished app uses fewer colors, fewer font sizes, fewer spacing values, and fewer words — but uses them consistently. Over-engineering visual elements (custom gradients, decorative borders, bespoke dividers) creates visual noise. Native components and system colors create harmony.

Attention is scarce. Keep UI copy shorter than you think it needs to be. Prefer one clear headline and one compact supporting block over repeated explanation in the title, subtitle, body, and footer. If a screen needs rationale, put it in one purposeful place instead of scattering it across the page.

1. Spacing System: Use a Consistent Grid

CRITICAL: Use spacing values from a base-4/base-8 grid. Never use arbitrary values.

Allowed spacing values

4, 8, 12, 16, 20, 24, 32, 40, 48

Bad (arbitrary values that create visual dissonance)

swift
// WRONG - these numbers have no relationship to each other.padding(.bottom, 26).padding(.bottom, 34).padding(.bottom, 36)HStack(spacing: 18).padding(14)

Good (values from a consistent grid)

swift
// RIGHT - predictable rhythm the eye can follow.padding(.horizontal, 20).padding(.top, 8)Spacer().frame(height: 32)HStack(spacing: 4)  // or 8, 12, 16.padding(.vertical, 12).padding(.horizontal, 16)

Standard padding assignments

  • Outer content padding: 16-20pt horizontal
  • Between major sections: 24-32pt vertical
  • Within grouped components: 4-12pt
  • Card/row internal padding: 12-16pt vertical, 16pt horizontal

2. Typography: Hierarchy Through Weight, Not Just Size

The principle

Use fewer font sizes with clear weight differentiation. Lighter weights at larger sizes; medium/regular at smaller sizes. This creates sophistication rather than visual chaos.

Recommended type scale (for a data-focused app)

RoleSizeWeightNotes
Hero number36-42pt.lightLarge but visually light -- elegant, not heavy
Secondary stat20-24pt.lightSame weight family as hero, smaller
Body / toggle label15pt.regularStandard iOS body size
Section header (uppercase)11pt.mediumWith tracking/letter-spacing
Caption / subtitle11-13pt.regularSecondary information

Bad (too many sizes, inconsistent weights)

swift
// WRONG - 7 different sizes with no clear system.font(.system(size: 60, weight: .ultraLight))   // hero.font(.system(size: 44, weight: .regular))        // stat (too close to hero).font(.system(size: 31, weight: .ultraLight))     // percent symbol (odd ratio).font(.system(size: 18, weight: .regular))        // label (too big for a toggle).font(.system(size: 14, weight: .regular))        // header.font(.system(size: 13, weight: .regular))        // another header.font(.system(size: 12, weight: .regular))        // button (too small to read)

Good (clear hierarchy, fewer sizes)

swift
// RIGHT - 5 sizes, clear purpose for each.font(.system(size: 42, weight: .light, design: .monospaced))    // hero.font(.system(size: 24, weight: .light, design: .monospaced))    // stat value.font(.system(size: 15, weight: .regular, design: .monospaced))  // body.font(.system(size: 14, weight: .regular, design: .monospaced))  // secondary.font(.system(size: 11, weight: .medium, design: .monospaced))   // label

Font design consistency

Pick ONE font design and use it everywhere -- app AND widgets:

swift
// If using monospaced, use it everywheredesign: .monospaced  // app views, widgets, lock screen -- all of them
// NEVER mix designs between app and widgets// BAD: .monospaced in app, .rounded in lock screen widget

Letter spacing (tracking)

Use at most 2 values, and only on uppercase labels:

swift
.tracking(1.5)  // section labels: "NOTIFICATIONS", "DAY", "LEFT".tracking(3)    // navigation/toolbar titles

Never use 3+ different tracking values like kerning(4), kerning(4.5), kerning(5) -- the differences are imperceptible but the inconsistency registers subconsciously.

Numeric formatting for identifiers

Years and other fixed identifiers should not be locale-grouped.

swift
// RIGHT - stable, non-grouped identifier textText(String(year))                  // "2026"Text(year, format: .number.grouping(.never))
// WRONG - locale grouping can render "2,026"Text("\(year)")

3. Colors: System Semantic Colors Over Hardcoded Values

The principle

Use SwiftUI's semantic color system. It automatically handles light/dark mode, accessibility, and looks native. Hardcoded colors with manual opacity values create maintenance nightmares and look artificial.

Bad (hardcoded white with a dozen opacity values)

swift
// WRONG - impossible to maintain, doesn't adapt to light modeColor.black.ignoresSafeArea()           // forced darkColor.white.opacity(0.08)               // ring backgroundColor.white.opacity(0.09)               // dividerColor.white.opacity(0.3)                // year textColor.white.opacity(0.32)               // stat labelColor.white.opacity(0.42)               // percent symbolColor.white.opacity(0.44)               // toggle tintColor.white.opacity(0.72)               // button textColor.white.opacity(0.88)               // toggle labelColor.white.opacity(0.9)                // stat valueColor.white.opacity(0.94)               // ring fill

Good (semantic system colors)

swift
// RIGHT - adapts automatically, looks native, easy to maintainColor(.systemBackground)                 // main backgroundColor(.secondarySystemBackground)        // card/group backgroundsColor(.separator)                        // dividers (with optional opacity)Color.primary                            // primary text and UI elements.foregroundStyle(.secondary)              // secondary text.foregroundStyle(.tertiary)               // labels, captions

When you do need opacity

Limit to 2-3 values with clear purposes:

swift
.opacity(0.15)  // subtle background strokes.opacity(0.3)   // separator lines// That's it. If you need more, you're probably hardcoding what semantic colors handle.

4. Component Sizing: Proportional, Not Oversized

Progress rings / circular indicators

swift
// App main view: 200x200 with thin stroke.frame(width: 200, height: 200)Circle().stroke(..., lineWidth: 3)
// Widget (systemSmall): 90x90, same stroke.frame(width: 90, height: 90)Circle().stroke(..., lineWidth: 3)
// WRONG: oversized ring with thick inconsistent strokes.frame(width: 260, height: 260)    // too large, dominates screenCircle().stroke(..., lineWidth: 9)  // backgroundCircle().stroke(..., lineWidth: 8)  // fill -- WHY different from background?

Stroke width consistency

Always use the same lineWidth for background and foreground strokes of the same element:

swift
// RIGHTCircle().stroke(background, lineWidth: 3)Circle().trim(from: 0, to: fraction).stroke(fill, lineWidth: 3)
// WRONG - creates visual misalignmentCircle().stroke(background, lineWidth: 9)Circle().trim(from: 0, to: fraction).stroke(fill, lineWidth: 8)

List rows and toggle rows

swift
// RIGHT - natural sizing with proper paddingToggle(isOn: $value) {    Text(title)        .font(.system(size: 15, weight: .regular, design: .monospaced))}.padding(.horizontal, 16).padding(.vertical, 12)
// WRONG - fixed oversized heightHStack {    Text(label)        .font(.system(size: 18))   // too big for a toggle label    Spacer()    Toggle("", isOn: $isOn)        .labelsHidden()             // why hide the label? Use Toggle properly}.frame(height: 70)                  // way too tall

5. Grouped Content & Cards: Use System Patterns

Bad (over-engineered custom card)

swift
// WRONG - custom gradient, overlay border, huge corner radiusVStack { ... }    .padding(.vertical, 4)              // too tight    .background(        RoundedRectangle(cornerRadius: 22)   // too round            .fill(LinearGradient(            // unnecessary gradient                colors: [Color(white: 0.10), Color(white: 0.085)],                startPoint: .topLeading, endPoint: .bottomTrailing            ))    )    .overlay(        RoundedRectangle(cornerRadius: 22)            .stroke(Color.white.opacity(0.08), lineWidth: 1)  // decorative border    )

Good (native grouped style)

swift
// RIGHT - simple, native, works in light and dark modeVStack(spacing: 0) {    row1    Divider().padding(.leading, 16)    row2    Divider().padding(.leading, 16)    row3}.background(Color(.secondarySystemBackground)).clipShape(.rect(cornerRadius: 10))

Key rules for grouped content

  • Corner radius: 10pt for cards/groups (matches iOS system style). Never 22pt+.
  • Dividers: Use the system Divider() with .padding(.leading, 16) for iOS-standard inset. Never build custom divider structs.
  • Card padding: 12-16pt vertical, 16pt horizontal. Never 4pt vertical.
  • Background: Color(.secondarySystemBackground) -- never custom gradients for standard cards.

6. Navigation: Use NavigationStack

swift
// RIGHT - proper navigation with minimal toolbarNavigationStack {    ScrollView {        content    }    .toolbar {        ToolbarItem(placement: .principal) {            Text("Title")                .font(.system(size: 13, weight: .medium, design: .monospaced))                .tracking(3)                .foregroundStyle(.tertiary)        }    }    .navigationBarTitleDisplayMode(.inline)}
// WRONG - no navigation structure, just a ZStackZStack {    Color.black.ignoresSafeArea()    ScrollView {        VStack {            Text("2026").font(...) // manually placed "title"            content        }    }}

7. WidgetKit: Use Native Components

Circular lock screen widget

swift
// RIGHT - use Gauge, it's purpose-built for thisGauge(value: entry.fraction) {    Text("")} currentValueLabel: {    Text("\(Int(entry.percentage))%")        .font(.system(size: 12, weight: .medium, design: .monospaced))}.gaugeStyle(.accessoryCircular).containerBackground(.fill.tertiary, for: .widget)
// WRONG - manual circle drawing for lock screenZStack {    Circle().stroke(Color.primary.opacity(0.18), lineWidth: 4)    Circle().trim(from: 0, to: progress).stroke(...)    Text(percentText)        .font(.system(size: 14, weight: .bold, design: .rounded)) // wrong font design!}

Rectangular lock screen widget

swift
// RIGHT - use Gauge with linearCapacityVStack(alignment: .leading, spacing: 4) {    HStack {        Text(year).font(.system(size: 13, weight: .semibold, design: .monospaced))        Spacer()        Text(percentage).font(.system(size: 13, weight: .medium, design: .monospaced))            .foregroundStyle(.secondary)    }    Gauge(value: fraction) { Text("") }        .gaugeStyle(.linearCapacity)        .tint(.primary)    HStack {        Spacer()        Text("\(dayOfYear)/\(totalDays)")            .font(.system(size: 11, weight: .regular, design: .monospaced))            .foregroundStyle(.secondary)    }}.containerBackground(.fill.tertiary, for: .widget)
// WRONG - custom GeometryReader progress barGeometryReader { proxy in    ZStack(alignment: .leading) {        RoundedRectangle(cornerRadius: 2).fill(Color.primary.opacity(0.16))        RoundedRectangle(cornerRadius: 2).fill(Color.primary)            .frame(width: max(2, proxy.size.width * progress))    }}.frame(height: 6)

Widget background

swift
// RIGHT.containerBackground(.fill.tertiary, for: .widget)
// WRONG - hardcoded color.containerBackground(.black, for: .widget)

Widget family coverage

Support all relevant families -- don't skip common ones:

swift
.supportedFamilies([    .accessoryCircular,      // lock screen circle    .accessoryRectangular,   // lock screen rectangle    .accessoryInline,        // lock screen inline text    .systemSmall,            // home screen small    .systemMedium,           // home screen medium    .systemLarge,            // home screen large])

Cross-family visual consistency

Medium and large home widgets should share the same structural layout:

  • Header: year on the left, percentage on the right
  • Middle: progress bar
  • Footer: day/total right aligned

Do not re-invent hierarchy per family unless there is a hard size constraint.

Always include explicit internal padding on home widgets to avoid clipping near rounded edges:

swift
.padding(.horizontal, 12).padding(.vertical, 12)

Widget memory budget (hard limit)

Widget extensions have a tight memory budget (commonly around 30 MB). Dense visualizations can be killed by EXC_RESOURCE if built from too many nested views.

swift
// RIGHT - draw dense dot grids in one passCanvas { context, size in    // draw 365/366 dots here}
// WRONG - hundreds of nested subviews (high memory overhead)LazyVGrid(columns: columns) {    ForEach(1...366, id: \.self) { day in        ZStack { Circle(); partialFillLayer }    }}

Timeline refresh (match data granularity)

swift
// RIGHT - refresh at midnight for day-level datalet tomorrow = calendar.startOfDay(for: calendar.date(byAdding: .day, value: 1, to: now)!)Timeline(entries: [entry], policy: .after(tomorrow))
// RIGHT - periodic refresh for time-of-day dependent percentages/partial fillslet refresh = Calendar.current.date(byAdding: .minute, value: 15, to: now)!Timeline(entries: [entry], policy: .after(refresh))
// WRONG - minute-level refresh for static daily datalet tooFrequent = Calendar.current.date(byAdding: .minute, value: 1, to: now)!Timeline(entries: [entry], policy: .after(tooFrequent))

8. Interactive Elements

Toggles

swift
// RIGHT - use Toggle with its built-in label, tint with a single accent colorToggle(isOn: $value) {    Text(title)        .font(.system(size: 15, weight: .regular, design: .monospaced))}.tint(.green)
// WRONG - hidden label with manual HStack layoutHStack {    Text(label).font(.system(size: 18))    Spacer()    Toggle("", isOn: $isOn)        .labelsHidden()        .tint(Color.white.opacity(0.44))  // low-contrast tint}

Mutually exclusive options

When options are exclusive (e.g. daily/weekly/monthly cadence), use one selected value, not three independent toggles.

swift
// RIGHT - single source of truthenum Cadence: String, CaseIterable { case daily, weekly, monthly }@State private var cadence: Cadence = .daily
ForEach(Cadence.allCases, id: \.rawValue) { option in    Button {        cadence = option    } label: {        HStack {            Image(systemName: cadence == option ? "checkmark.circle.fill" : "circle")            Text(option.rawValue.capitalized)        }    }}
// RIGHT - one preview action when content is sharedButton("Preview") { sendPreview() }
// WRONG - independent toggles allow contradictory stateToggle("Daily", isOn: $daily)Toggle("Weekly", isOn: $weekly)Toggle("Monthly", isOn: $monthly)

Animated transitions for changing numbers

swift
// Add to any Text that displays a changing numeric valueText(String(format: "%.2f", percentage))    .contentTransition(.numericText())

9. Interactive Editors: Centralize Geometry and State

Interactive editors (collages, crops, canvases, media framing tools, layout pickers) need stricter state and layout discipline than ordinary forms.

Presentation state

Present editor flows from payload state, not from a separate Bool plus independently-managed data.

swift
// RIGHT - presentation only happens when payload exists@State private var activeCropRequest: CropRequest?
.sheet(item: $activeCropRequest) { request in    CropEditor(request: request)}
// WRONG - the sheet can open before the backing data is ready@State private var showCropEditor = false@State private var selectedImage: UIImage?
.sheet(isPresented: $showCropEditor) {    if let selectedImage { CropEditor(image: selectedImage) }}

Shared geometry model

If the app previews pan/zoom/crop/layout live and later exports the result, use one shared geometry model for both preview and render.

swift
// RIGHT - one source of truth for bounds and transformslet normalized = EditorGeometry.normalizedAdjustment(adjustment, imageSize: image.size, slotSize: slotSize)let drawRect = EditorGeometry.drawRect(for: image.size, in: slotRect, adjustment: adjustment)
// WRONG - preview and export each invent their own mathlet previewOffset = ...let exportOffset = ...

If a user can zoom out enough to reveal background, that must be an intentional part of the shared geometry model, not an editor-only exception.

Gesture coordination

Tap, long-press-drag, and pinch are not independent features. In SwiftUI they compete unless you model their relationship explicitly.

  • Use a single interaction state for the active tile/card/canvas item.
  • Decide which gesture has priority and which ones should run simultaneously.
  • Reset temporary gesture state deliberately when selection changes.
  • Prefer one coherent state machine over scattered booleans tied to individual gestures.

Fixed editor layout

If the screen must not scroll, budget vertical space top-down using a few named regions:

  • header
  • canvas stage
  • settings region
  • bottom toolbar

Keep that sizing math in one place. Don't let each subview invent its own height.

Custom headers and safe areas

If you replace the system navigation bar with a custom header:

  • Be explicit about whether the parent already respects the safe area.
  • Do not add safeAreaInsets.top reflexively; double-counting it creates obvious dead space.
  • Keep custom headers compact. They should feel like navigation chrome, not a full content section.

Settings surfaces

When an editor has several configuration modes (Layout, Border, Ratio, Background, etc.), show one active settings surface at a time instead of stacking every control on screen.

This keeps the canvas visually dominant and makes each control group easier to understand.

10. Data Model: Share Between App and Widgets

swift
// RIGHT - one model used everywherestruct YearProgress {    // shared calculation logic    static func current() -> YearProgress { ... }}// Used by both ContentView and widget TimelineProvider
// If percentage is shown as live progress, include time-of-day in shared mathlet dayProgress = elapsedInCurrentDay / totalSecondsInDaylet elapsedDays = Double(dayOfYear - 1) + dayProgresslet fraction = elapsedDays / Double(totalDays)
// WRONG - separate snapshot structs with duplicated date mathstruct YearProgressSnapshot { ... }            // in appstruct YearProgressWidgetSnapshot { ... }      // in widget extension (duplicated!)

11. Quick Checklist

Before shipping any SwiftUI view, verify:

  • All spacing values come from the grid (4, 8, 12, 16, 20, 24, 32)
  • Font sizes limited to 5 or fewer distinct values
  • One font design used consistently (including widgets)
  • Colors use semantic system colors, not hardcoded values with opacity
  • Background and foreground strokes use the same lineWidth
  • Cards use Color(.secondarySystemBackground) with 10pt corner radius
  • Dividers use system Divider() with leading padding
  • Toggle rows use Toggle's built-in label (not .labelsHidden())
  • Lock screen widgets use Gauge (not manual circle drawing)
  • Widget background uses .containerBackground(.fill.tertiary, for: .widget)
  • Year/identifier text avoids locale grouping when grouping is not desired
  • Tracking/kerning limited to 2 values max
  • NavigationStack is used (not bare ZStack)
  • Timeline refresh rate matches data granularity (midnight vs periodic)
  • Large/dense widget visuals use Canvas or similarly lightweight rendering
  • Medium and large widget families share consistent hierarchy and internal padding
  • Exclusive choices use a single selected value (not multiple toggles)
  • Percentages include time-of-day when UI implies live progress
  • No minimumScaleFactor hacks -- fix the layout instead
  • Interactive editors present from payload state, not Bool + separate data
  • Preview and export share the same geometry model for pan/zoom/crop/layout
  • Custom headers do not double-count top safe-area inset
  • No-scroll editor screens budget height through a centralized layout model
  • Multi-mode editors show one focused settings surface instead of every control at once

Source and attribution

Source:arjitj2/swiftui-design-principlesat commit791d22d

License: MIT

Content belongs to its original authors. SourceWeft indexes it from a public repository.

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