Expo UI Guidelines

References

Consult these resources as needed:

./references/route-structure.md -- Route file conventions, dynamic routes, query parameters, groups, and folder organization
./references/tabs.md -- Native tab bar with NativeTabs, migration from JS tabs, iOS 26 features
./references/icons.md -- SF Symbols with expo-symbols, common icon names, animations, and weights
./references/controls.md -- Native iOS controls: Switch, Slider, SegmentedControl, DateTimePicker, Picker
./references/visual-effects.md -- Blur effects with expo-blur and liquid glass with expo-glass-effect
./references/animations.md -- Reanimated animations: entering, exiting, layout, scroll-driven, and gestures
./references/search.md -- Search bar integration with headers, useSearch hook, and filtering patterns
./references/gradients.md -- CSS gradients using experimental_backgroundImage (New Architecture only)
./references/media.md -- Media handling for Expo Router including camera, audio, video, and file saving
./references/storage.md -- Data storage patterns including SQLite, AsyncStorage, and SecureStore
./references/webgpu-three.md -- 3D graphics, games, and GPU-powered visualizations with WebGPU and Three.js

Running the App

CRITICAL: Always try Expo Go first before creating custom builds.

Most Expo apps work in Expo Go without any custom native code. Before running npx expo run:ios or npx expo run:android:

Start with Expo Go: Run npx expo start and scan the QR code with Expo Go
Check if features work: Test your app thoroughly in Expo Go
Only create custom builds when required - see below

When Custom Builds Are Required

Local Expo modules (custom native code in modules/ directory)
Apple targets (widgets, app clips, extensions)
Third-party native modules not included in Expo Go
Push notifications with custom configuration

When Expo Go Works

Standard Expo SDK modules
Expo Router navigation
React Native Reanimated animations
Most UI components and styling

Code Style

Be cautious of unterminated strings. Ensure nested backticks are escaped; never forget to escape quotes correctly.
Always use import statements at the top of the file.
Always use kebab-case for file names, e.g. comment-card.tsx
Always remove old route files when moving or restructuring navigation
Never use special characters in file names
Configure tsconfig.json with path aliases, and prefer aliases over relative imports for refactors.

Routes

See ./references/route-structure.md for detailed route conventions.

Routes belong in the app directory.
Never co-locate components, types, or utilities in the app directory. This is an anti-pattern.
Ensure the app always has a route that matches "/", it may be inside a group route.

Library Preferences

Never use modules removed from React Native such as Picker, WebView, SafeAreaView, or AsyncStorage
Never use legacy expo-permissions
expo-audio not expo-av
expo-video not expo-av
expo-symbols not @expo/vector-icons
react-native-safe-area-context not react-native SafeAreaView
process.env.EXPO_OS not Platform.OS
React.use not React.useContext
expo-image Image component instead of intrinsic element img
expo-glass-effect for liquid glass backdrops

Responsiveness

Always wrap root component in a scroll view for responsiveness
Use <ScrollView contentInsetAdjustmentBehavior="automatic" /> instead of <SafeAreaView> for smarter safe area insets
contentInsetAdjustmentBehavior="automatic" should be applied to FlatList and SectionList as well
Use flexbox instead of Dimensions API
ALWAYS prefer useWindowDimensions over Dimensions.get() to measure screen size

Behavior

Use expo-haptics conditionally on iOS to make more delightful experiences
Use views with built-in haptics like <Switch /> from React Native and @react-native-community/datetimepicker
When a route belongs to a Stack, its first child should almost always be a ScrollView with contentInsetAdjustmentBehavior="automatic" set
Prefer headerSearchBarOptions in Stack.Screen options to add a search bar
Use the <Text selectable /> prop on text containing data that could be copied
Consider formatting large numbers like 1.4M or 38k
Never use intrinsic elements like 'img' or 'div' unless in a webview or Expo DOM component

Styling

General Styling Rules

Use StyleSheet.create() for all styles
Prefer named colors from a theme/design system
Group related styles together
Use semantic naming for style objects

Text Styling

import { Text, StyleSheet } from 'react-native';

const styles = StyleSheet.create({
  title: {
    fontSize: 24,
    fontWeight: '700',
    color: '#1a1a1a',
  },
  body: {
    fontSize: 16,
    lineHeight: 24,
    color: '#4a4a4a',
  },
});

Shadows

iOS and Android handle shadows differently:

const styles = StyleSheet.create({
  card: {
    // iOS shadows
    shadowColor: '#000',
    shadowOffset: { width: 0, height: 2 },
    shadowOpacity: 0.1,
    shadowRadius: 8,
    // Android shadows
    elevation: 4,
    // Common
    backgroundColor: '#fff',
    borderRadius: 12,
  },
});

Navigation

Link

Use <Link href="/path" /> from 'expo-router' for navigation between routes.

import { Link } from 'expo-router';

// Basic link
<Link href="/path" />

// Wrapping custom components
<Link href="/path" asChild>
  <Pressable>...</Pressable>
</Link>

Whenever possible, include a <Link.Preview> to follow iOS conventions. Add context menus and previews frequently to enhance navigation.

Stack

ALWAYS use _layout.tsx files to define stacks
Use Stack from 'expo-router/stack' for native navigation stacks

Page Title

Set the page title using Stack.Screen options:

import { Stack } from 'expo-router';

export default function Layout() {
  return (
    <Stack>
      <Stack.Screen 
        name="index" 
        options={{ title: 'Home' }} 
      />
      <Stack.Screen 
        name="details" 
        options={{ title: 'Details' }} 
      />
    </Stack>
  );
}

Context Menus

Add context menus for enhanced interactions:

import { ContextMenu } from 'zeego/context-menu';

<ContextMenu.Root>
  <ContextMenu.Trigger>
    <Pressable>{/* content */}</Pressable>
  </ContextMenu.Trigger>
  <ContextMenu.Content>
    <ContextMenu.Item key="share" onSelect={handleShare}>
      <ContextMenu.ItemTitle>Share</ContextMenu.ItemTitle>
    </ContextMenu.Item>
  </ContextMenu.Content>
</ContextMenu.Root>

Modal

Present modals using the presentation option:

// In _layout.tsx
<Stack.Screen 
  name="modal" 
  options={{ 
    presentation: 'modal',
    headerShown: false,
  }} 
/>

Sheet

For bottom sheets, use:

<Stack.Screen 
  name="sheet" 
  options={{ 
    presentation: 'formSheet',
    sheetGrabberVisible: true,
    sheetInitialDetentIndex: 0,
    sheetAllowedDetents: [0.5, 1],
  }} 
/>

Common route structure

app/
├── _layout.tsx        # Root layout (Stack or Tabs)
├── index.tsx          # Home screen "/"
├── (tabs)/
│   ├── _layout.tsx    # Tab navigator
│   ├── index.tsx      # First tab
│   └── settings.tsx   # Settings tab
├── [id].tsx           # Dynamic route "/123"
└── modal.tsx          # Modal screen