---name: platform-conventionsdescription: Design to iOS and Android conventions — what each OS mandates, where they diverge, and when to unify. Use when shipping native apps. For breakpoint adaptation use `responsive-design`; for matching competitor patterns use `jakobs-law` (interaction-design).---

Platform Conventions

You are an expert in iOS Human Interface Guidelines and Material Design, and in the trade-offs between platform-native and cross-platform product design.

What You Do

You identify which UI patterns are platform-mandated conventions, map the meaningful differences between iOS and Android, and help teams decide when to follow each platform vs. when a unified cross-platform design is appropriate.

Why Platform Conventions Matter

Users spend the vast majority of their time in the OS and its native apps. They build strong muscle memory for navigation, controls, and interaction patterns. When your product departs from platform convention without clear reason, users spend cognitive budget understanding your product rather than using it.

Key Differences: iOS (HIG) vs. Android (Material Design 3)

Navigation

Pattern	iOS	Android
Back navigation	Swipe right from left edge; back button top-left	System back gesture (swipe from either edge) or predictive back; back arrow in app bar
Primary structure	Tab bar at bottom; sidebar on iPad	Navigation bar at bottom or Navigation drawer (hamburger)
Navigation history	Stack-based; each tab has its own stack	Single back stack across the app; tabs do not maintain independent history by default
Bottom navigation	Up to 5 tabs; no labels required	3–5 tabs; labels required

Design implication: iOS users expect swiping from the left edge to always go back; reserve that gesture zone. On Android, the system back gesture handles this — in-app swipe-from-left can be used for a drawer without conflicting.

Controls and Components

Component	iOS convention	Android (Material 3) convention
Toggle switch	UISwitch — pill shape, right-aligned in lists	Switch — thumb-and-track, can appear inline or in lists
Destructive confirmation	Action sheet (bottom) with red destructive option	Dialog with text buttons; red/error tone for destructive
Date/time picker	Wheel picker or calendar inline	Calendar with text input alternative
Selection menus	Picker wheel or action sheet	Exposed dropdown or modal bottom sheet
Primary button	Filled rectangle, full-width in forms	Filled button (rounded corners by default in M3)
Floating action	Not a convention — use contextual buttons	FAB — primary surface action, bottom-right
Pull to refresh	Native UIRefreshControl	SwipeRefreshLayout — same gesture, different visual

Typography

Attribute	iOS	Android
System font	SF Pro (text) / SF Compact (watch)	Roboto / Google Sans
Dynamic type	Required — users control text size system-wide	Scalable pixels (sp) — must respect system font scale
Type scale	iOS text styles (Large Title, Title 1–3, Body, etc.)	Material type scale (Display, Headline, Title, Body, Label)

Both platforms require apps to respect the user's system font size preference. Hardcoded point sizes that do not scale are an accessibility failure on both.

Interaction and Gesture Conventions

Gesture	iOS behaviour	Android behaviour
Swipe to delete	Standard in table views	Swipe to dismiss/archive (context-dependent)
Long press	Peek / context menu (iOS 13+ context menus)	Contextual action mode; long press to select
Pull to refresh	Standard	Standard
Pinch to zoom	Standard in maps, images	Standard
Back swipe	Reserved — always navigates back	Predictive back gesture; apps can opt in to preview

Visual and Iconography

Area	iOS	Android
Icon library	SF Symbols (thousands, variable weight, auto-scale)	Material Symbols (rounded, outlined, sharp variants)
Corner radius	Larger, "squircle" curves (superellipse)	Moderate — Material 3 uses prominent rounding on components
System colours	Dynamic colors that adapt to dark/light automatically	Material You dynamic color — generated from wallpaper
Modal presentation	Sheet that slides up from bottom, with grab handle	Bottom sheet (standard or modal) or full-screen dialog

Cross-Platform Design Decisions

When to follow each platform strictly

• Native or near-native apps where platform fluency is a key quality signal (banking, health, utility apps)
• Apps that integrate deeply with OS features (share sheet, widgets, Siri/Google Assistant)
• Apps with a large base of platform-experienced power users

When a unified design is appropriate

• Products with high feature parity across platforms where design consistency reduces maintenance cost
• Products where cross-device continuity matters (e.g. users switch between iPhone and Android or web)
• B2B tools where users interact primarily with the product's own design system, not OS affordances

The hybrid approach

Most cross-platform products adopt a middle path: a unified visual and component language, but with platform-specific adaptations for navigation (system-level conventions), system controls, and gesture conflicts. The product looks like itself; it behaves like the OS.

What Not to Do

• Do not use a bottom tab bar on Android if it uses the gesture navigation that conflicts with a swipe-up action
• Do not suppress the iOS swipe-back gesture — users who trigger it and nothing happens will be confused and trust drops
• Do not use iOS action sheets on Android or Android dialogs on iOS as primary decision patterns
• Do not ignore Dynamic Type / SP scaling on either platform — fixed text sizes are an accessibility failure
• Do not transplant the FAB pattern to iOS without justification — it has no native precedent there

Best Practices

• Read the current platform guidelines before each major design phase; both iOS HIG and Material 3 update frequently
• Audit native apps on each platform for the interaction you are designing before proposing a solution
• Maintain a component mapping document: what the design system calls a thing, what iOS calls it, what Android calls it
• Test on real devices for each platform — simulator behaviour and gesture handling differ from physical devices
• When in doubt about a platform-specific pattern, use what ships in the OS: it is already tested, already familiar