app-ui-design

Mobile App UI Design

Expert guidance for designing beautiful, accessible, and platform-native mobile app interfaces following 2025 best practices.

Core Philosophy User-First Design — Prioritize user needs, behaviors, and mental models over aesthetics Platform Consistency — Follow iOS HIG and Android Material Design guidelines Accessibility as Foundation — Design for all users from the start, not as an afterthought Emotional Intelligence — Create interfaces that users emotionally connect with Performance-Conscious — Beautiful design that doesn't sacrifice app performance Hard Rules (Must Follow)

These rules are mandatory. Violating them means the skill is not working correctly.

Accessibility First

All designs must meet WCAG 2.2 AA standards. Accessibility is not optional.

❌ FORBIDDEN: - Color contrast below 4.5:1 for text - Touch targets smaller than 44×44pt (iOS) or 48×48dp (Android) - Information conveyed by color alone - Missing alternative text for images - Non-keyboard-navigable interfaces

✅ REQUIRED: - Minimum 4.5:1 contrast ratio for normal text - Minimum 3:1 contrast ratio for large text (18pt+) - Touch targets: 44×44pt (iOS) / 48×48dp (Android) - Support for Dynamic Type / Font Scaling - VoiceOver (iOS) / TalkBack (Android) compatibility - Clear focus indicators for keyboard navigation

Platform Guidelines Adherence

Follow platform-specific design guidelines. Do not mix iOS and Android patterns.

❌ FORBIDDEN: - Using Android-style FAB on iOS - Using iOS-style bottom sheets on Android without adaptation - Mixing platform navigation patterns - Ignoring platform typography (SF Pro vs Roboto)

✅ REQUIRED: iOS (Human Interface Guidelines): - Use SF Pro font family - Tab bar at bottom for primary navigation - Push navigation with back chevron - Standard iOS controls (UIKit/SwiftUI)

Android (Material Design 3): - Use Roboto font family - Bottom navigation bar or navigation drawer - Material components with ripple effects - Follow Material You dynamic theming

Consistent Design System

Every app must have a documented design system with tokens.

❌ FORBIDDEN: - Ad-hoc colors and spacing values - Inconsistent button styles across screens - Multiple unnamed font sizes - Components without defined states

✅ REQUIRED: Design System Must Include: ├── Color Tokens (primary, secondary, surface, error, etc.) ├── Typography Scale (heading1-6, body, caption, etc.) ├── Spacing Scale (4, 8, 12, 16, 24, 32, 48px) ├── Border Radius Tokens (none, sm, md, lg, full) ├── Shadow/Elevation Tokens (elevation1-5) └── Component Library (button, input, card, etc.)

Touch-Friendly Design

All interactive elements must be optimized for touch interaction.

❌ FORBIDDEN: - Touch targets smaller than minimum size - Interactive elements too close together (<8px gap) - Important actions outside thumb reach zone - Hover-dependent interactions

✅ REQUIRED: - Minimum touch target: 44×44pt (iOS) / 48×48dp (Android) - Minimum spacing between targets: 8px - Primary actions in thumb-friendly zone (bottom 2/3) - Clear tap feedback (ripple, highlight, scale)

Quick Reference When to Use What Scenario Approach Key Considerations New app design Start with design system Define tokens before screens iOS-only app Human Interface Guidelines SF Pro, standard iOS patterns Android-only app Material Design 3 Roboto, Material components Cross-platform app Adaptive design Platform-specific navigation Redesign existing app Audit first Maintain mental models Accessibility review WCAG 2.2 AA checklist Contrast, touch targets, labels Design System Fundamentals Color System

Color Token Structure

Semantic Colors

primary → Main brand color, CTAs primary-variant → Darker/lighter primary for states secondary → Secondary actions, accents background → App background surface → Card backgrounds, elevated surfaces error → Error states, destructive actions on-primary → Text/icons on primary color on-background → Text/icons on background on-surface → Text/icons on surface

Color Palette (60-30-10 Rule)

60% → Neutral/background colors 30% → Secondary/supporting colors 10% → Accent/primary colors

Dark Mode Considerations

• Don't just invert colors
• Use desaturated colors for dark surfaces
• Reduce contrast slightly (avoid pure white on black)
• Maintain color meaning across modes

Typography Scale

Mobile Typography Guidelines

iOS Typography (SF Pro)

Large Title → 34pt, Bold Title 1 → 28pt, Bold Title 2 → 22pt, Bold Title 3 → 20pt, Semibold Headline → 17pt, Semibold Body → 17pt, Regular Callout → 16pt, Regular Subhead → 15pt, Regular Footnote → 13pt, Regular Caption 1 → 12pt, Regular Caption 2 → 11pt, Regular

Android Typography (Roboto / Material 3)

Display Large → 57sp Display Medium → 45sp Display Small → 36sp Headline Large → 32sp Headline Medium→ 28sp Headline Small → 24sp Title Large → 22sp Title Medium → 16sp, Medium Title Small → 14sp, Medium Body Large → 16sp Body Medium → 14sp Body Small → 12sp Label Large → 14sp, Medium Label Medium → 12sp, Medium Label Small → 11sp, Medium

Best Practices

• Maximum 2-3 font families per app
• Minimum body text: 16px (14px absolute minimum)
• Line height: 1.4-1.6× font size for body text
• Support Dynamic Type (iOS) / Font Scaling (Android)

Spacing System

8-Point Grid System

Base Unit: 8px

Spacing Scale

spacing-0 → 0px spacing-1 → 4px (half unit) spacing-2 → 8px (1 unit) spacing-3 → 12px (1.5 units) spacing-4 → 16px (2 units) spacing-5 → 24px (3 units) spacing-6 → 32px (4 units) spacing-7 → 48px (6 units) spacing-8 → 64px (8 units)

Component Spacing

Button padding → 12px vertical, 24px horizontal Card padding → 16px List item padding → 16px horizontal, 12px vertical Section spacing → 24px-32px Screen edge margin → 16px (phones), 24px (tablets)

Touch Target Spacing

Minimum gap between interactive elements: 8px Recommended gap: 12-16px

Platform Guidelines iOS Human Interface Guidelines

iOS Design Principles

Core Principles

1. Clarity → Text legible, icons precise, purpose obvious
2. Deference → UI helps understanding, not competing with content
3. Depth → Visual layers and realistic motion convey hierarchy

Navigation Patterns

• Tab Bar (bottom) → 3-5 primary destinations
• Navigation Bar (top) → Title, back button, actions
• Modal sheets → Temporary focused tasks
• Popovers (iPad) → Contextual options

2025 Updates: Liquid Glass

• Translucent materials for controls
• Floating navigation elements
• Dynamic depth and hierarchy
• Background blur effects

Safe Areas

• Top: Status bar + Dynamic Island/Notch
• Bottom: Home indicator (34pt on Face ID devices)
• Use safeAreaInsets for proper content placement

Standard Dimensions

• Navigation bar height: 44pt (96pt with large title)
• Tab bar height: 49pt (83pt on Face ID devices)
• Toolbar height: 44pt

Android Material Design 3

Material Design 3 Principles

Core Concepts

1. Material You → Personal, adaptive, dynamic color
2. Expressiveness → Emotional connection through design
3. Accessibility → Inclusive design for all users

Navigation Patterns

• Bottom Navigation → 3-5 primary destinations
• Navigation Drawer → 5+ destinations or secondary nav
• Navigation Rail → Tablets and large screens
• Top App Bar → Title, navigation, actions

Material 3 Expressive (2025)

• Dynamic color from user wallpaper
• Springy, physics-based motion
• Bolder, more expressive typography
• Rounded, approachable shapes

Component Shapes

• Extra Small: 4dp
• Small: 8dp
• Medium: 12dp
• Large: 16dp
• Extra Large: 28dp
• Full: 50% (pills/circles)

Standard Dimensions

• App bar height: 64dp
• Bottom navigation height: 80dp
• FAB size: 56dp (standard), 40dp (small), 96dp (large)

2025 Design Trends AI-Driven Personalization

Adaptive UI Patterns

Personalization Strategies

• Content recommendations based on behavior
• Adaptive UI layouts based on usage patterns
• Smart defaults and predictive actions
• Contextual feature suggestions

Implementation Guidelines

• Always provide manual override options
• Explain why content is recommended
• Respect user privacy preferences
• Gradual personalization (don't overwhelm new users)

Dark Mode Excellence

Dark Mode Best Practices

Color Adaptation

Light Mode → Dark Mode White (#FFFFFF) → Dark gray (#121212) Black (#000000) → White (#FFFFFF) Primary (vibrant) → Primary (desaturated) Shadows → Subtle shadows or none

Surface Elevation (Material 3)

Elevation 0 → #121212 Elevation 1 → #1E1E1E (+ 5% white overlay) Elevation 2 → #232323 (+ 7% white overlay) Elevation 3 → #272727 (+ 8% white overlay) Elevation 4 → #2C2C2C (+ 9% white overlay) Elevation 5 → #323232 (+ 11% white overlay)

Recommendations

• Auto-switch based on system setting
• Separate color tokens for light/dark
• Test contrast in both modes
• Consider OLED optimization (true blacks)

Microinteractions

Meaningful Motion

Types of Microinteractions

• Feedback → Button press, form submission
• State → Loading, success, error
• Guidance → Onboarding hints, tooltips
• Delight → Celebration animations, easter eggs

Motion Principles

• Duration: 200-500ms for most interactions
• Easing: Use natural easing curves
• Purpose: Every animation should have a reason
• Performance: Use hardware-accelerated properties

2025 Trends

• Springy, physics-based animations
• Morphing transitions between states
• Gesture-driven interactions
• Reduced motion support for accessibility

Glassmorphism & Neumorphism

Modern Visual Styles

Glassmorphism

Properties: - Background blur (backdrop-filter: blur) - Transparency (10-40% opacity) - Subtle border (1px white at 20% opacity) - Soft shadow

Use Cases: - Overlays and modals - Cards on image backgrounds - Navigation bars (iOS Liquid Glass)

Caution: - Ensure text readability - Consider performance impact - Provide fallback for older devices

Neumorphism (Soft UI)

Properties: - Soft shadows (light and dark) - Subtle elevation effect - Muted color palette

Use Cases: - Toggle switches - Input fields - Cards

Caution: - Often fails accessibility contrast tests - Use sparingly, not as primary style - Always test with actual content

Accessibility Checklist Visual Accessibility

Vision Accessibility Checklist

Color & Contrast

• [ ] Text contrast ≥ 4.5:1 (normal), ≥ 3:1 (large)
• [ ] UI component contrast ≥ 3:1
• [ ] Color is not the only indicator (use icons, text)
• [ ] Works for colorblind users (test with simulators)

Text & Typography

• [ ] Base font size ≥ 16px
• [ ] Supports Dynamic Type (iOS) / Font Scaling (Android)
• [ ] Line height ≥ 1.4× for body text
• [ ] Text can scale to 200% without loss of content

Focus & Navigation

• [ ] Visible focus indicators
• [ ] Logical tab order
• [ ] Skip links for repetitive content
• [ ] Keyboard-accessible (external keyboards)

Motor Accessibility

Motor Accessibility Checklist

Touch Targets

• [ ] Minimum size: 44×44pt (iOS) / 48×48dp (Android)
• [ ] Spacing between targets ≥ 8px
• [ ] No time-limited interactions (or extendable)
• [ ] Alternative to drag gestures (WCAG 2.2)

Interaction

• [ ] Single-tap for all actions (no double-tap required)
• [ ] Undo available for destructive actions
• [ ] No precision requirements (fine motor)
• [ ] Support for Switch Control / Voice Access

Screen Reader

Screen Reader Checklist

Content

• [ ] All images have descriptive alt text
• [ ] Decorative images have empty alt (alt="")
• [ ] Buttons/links have descriptive labels
• [ ] Form inputs have associated labels
• [ ] Headings used for structure (not styling)

Navigation

• [ ] Logical reading order
• [ ] Meaningful link text (not "click here")
• [ ] State changes announced
• [ ] Modal focus properly trapped
• [ ] Custom components have ARIA roles

Component Patterns Button Design

Button Hierarchy

Primary Button

• Most important action on screen
• Filled/solid style
• High contrast
• Only ONE per view section

Secondary Button

• Alternative actions
• Outlined or tonal style
• Medium contrast

Tertiary Button

• Low-priority actions
• Text-only or ghost style
• Subtle appearance

Destructive Button

• Delete, remove, cancel
• Red/error color
• Requires confirmation for important data

Button States

• Default → Normal appearance
• Pressed → Scale down, darker
• Disabled → 50% opacity, no interaction
• Loading → Spinner, disabled

Form Design

Form Best Practices

Input Fields

• Clear labels (above input, not placeholder-only)
• Helpful placeholder text
• Error states with specific messages
• Success validation feedback
• Appropriate keyboard types

Layout

• Single column for mobile
• Group related fields
• Logical tab order
• Primary action at bottom
• Sticky submit button if long form

Validation

• Inline validation (on blur or after input)
• Clear error messages with fix suggestions
• Don't clear fields on error
• Mark required fields clearly

Navigation Patterns

Mobile Navigation

Bottom Navigation (Primary)

• 3-5 destinations
• Icons + labels
• Active state indicator
• Consistent across app

Tab Bar (Content Switching)

• Horizontal tabs for related content
• Swipe between tabs
• Indicator for active tab

Navigation Stack

• Clear back navigation
• Meaningful titles
• Breadcrumbs for deep hierarchies

Gestures

• Swipe back (iOS standard)
• Pull to refresh
• Swipe actions on list items
• Long press for context menus

Design Process Workflow

App Design Workflow

1. Research & Discovery ├── User research and personas ├── Competitor analysis ├── Platform guidelines review └── Technical constraints

2. Information Architecture ├── User flows ├── Navigation structure ├── Content hierarchy └── Sitemap

3. Design System Setup ├── Color tokens ├── Typography scale ├── Spacing system ├── Component library └── Icon set

4. Wireframing ├── Low-fidelity layouts ├── Flow validation ├── Stakeholder review └── Iteration

5. Visual Design ├── High-fidelity mockups ├── Interaction design ├── Prototype creation └── Accessibility audit

6. Handoff & Implementation ├── Design specs documentation ├── Asset export ├── Developer collaboration └── QA review

Anti-Patterns to Avoid

Common Mistakes

Visual Design

❌ Using more than 3 fonts ❌ Inconsistent spacing values ❌ Low contrast text ❌ Overly complex gradients/effects ❌ Ignoring safe areas

Interaction Design

❌ Hidden navigation ❌ Gesture-only actions without alternatives ❌ Tiny touch targets ❌ No loading states ❌ Confusing back navigation

Accessibility

❌ Placeholder-only labels ❌ Color-only information ❌ Auto-playing media ❌ Timed interactions without extension ❌ Missing screen reader labels

Platform

❌ iOS patterns on Android (or vice versa) ❌ Custom controls when standard works ❌ Ignoring platform conventions ❌ Not supporting dark mode

Checklist Before Design Reviewed platform guidelines (iOS HIG / Material Design 3) Defined target users and their needs Analyzed competitor apps Identified accessibility requirements Set up design system tokens During Design Following 8-point grid Using defined color tokens Typography from scale only Touch targets meet minimum size Contrast ratios verified All states designed (default, pressed, disabled, error) Dark mode variant created Before Handoff Accessibility audit completed Tested with screen reader Verified on multiple screen sizes Motion/animation documented Design specs annotated Assets exported correctly Tools & Resources Design Tools Figma → Industry standard, collaboration Sketch → Mac-native, established ecosystem Adobe XD → Adobe integration Prototyping Figma Prototyping → Built-in, quick ProtoPie → Advanced interactions Principle → Mac, detailed animations Accessibility Testing Stark → Contrast checker (Figma plugin) Color Oracle → Colorblind simulator VoiceOver (iOS) / TalkBack (Android) Platform Resources Apple Human Interface Guidelines Google Material Design WCAG 2.2 Guidelines See Also reference/ios-guidelines.md — iOS Human Interface Guidelines summary reference/material-design.md — Material Design 3 summary reference/accessibility.md — WCAG 2.2 mobile checklist reference/color-theory.md — Color selection and contrast templates/design-system-template.md — Design system starter Sources

Research based on 2025 best practices from:

Mobile App UI Design Best Practices 2025 UI/UX Design Trends 2025 Mobile App Design Trends 2025 Accessibility in UI/UX Design 2025 iOS Design Guidelines 2025 Mobile App Design Guidelines iOS/Android