references/
  animations.md          Reanimated: entering, exiting, layout, scroll-driven, gestures
  controls.md            Native iOS: Switch, Slider, SegmentedControl, DateTimePicker, Picker
  form-sheet.md          Form sheets in expo-router: configuration, footers and background interaction.
  gradients.md           CSS gradients via experimental_backgroundImage (New Arch only)
  icons.md               SF Symbols via expo-image (sf: source), names, animations, weights
  media.md               Camera, audio, video, and file saving
  route-structure.md     Route conventions, dynamic routes, groups, folder organization
  search.md              Search bar with headers, useSearch hook, filtering patterns
  storage.md             SQLite, AsyncStorage, SecureStore
  tabs.md                NativeTabs, migration from JS tabs, iOS 26 features
  toolbar-and-headers.md Stack headers and toolbar buttons, menus, search (iOS only)
  visual-effects.md      Blur (expo-blur) and liquid glass (expo-glass-effect)
  webgpu-three.md        3D graphics, games, GPU visualizations with WebGPU and Three.js
  zoom-transitions.md    Apple Zoom: fluid zoom transitions with Link.AppleZoom (iOS 18+)

Running the App

Check required native modules before choosing Expo Go or a development build.

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

You need npx expo run:ios/android or eas build ONLY when using:

Local Expo modules (custom native code in modules/)
Apple targets (widgets, app clips, extensions via @bacons/apple-targets)
Third-party native modules not included in Expo Go
Custom native configuration that can't be expressed in app.json

When Expo Go Works

Expo Go supports a huge range of features out of the box:

Many Expo packages; check each module’s Expo Go and SDK compatibility.
Expo Router navigation
Most UI libraries (reanimated, gesture handler, etc.)
Supported navigation and development features; remote push and app-specific native configuration may require a development build.

If you're unsure, try Expo Go first. Creating custom builds adds complexity, slower iteration, and requires Xcode/Android Studio setup.

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-image with source="sf:name" for SF Symbols, or version-compatible expo-symbols; provide Android/web icon fallbacks
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
Color from expo-router for native semantic colors, not raw PlatformColor (type-safe, auto-adapts to light/dark)
In SDK 56+, never import from @react-navigation/* directly — use expo-router/react-navigation instead (covers @react-navigation/native, /core, /elements, /routers)

Responsiveness

Use ScrollView for bounded scrollable content and FlatList/SectionList for large collections; avoid nesting virtualized lists in same-direction ScrollViews.
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
When adding a ScrollView to the page it should almost always be the first component inside the route component
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

Follow Apple Human Interface Guidelines.

General Styling Rules

Prefer flex gap over margin and padding styles
Prefer padding over margin where possible
Always account for safe area, either with stack headers, tabs, or ScrollView/FlatList contentInsetAdjustmentBehavior="automatic"
Ensure both top and bottom safe area insets are accounted for
Inline styles not StyleSheet.create unless reusing styles is faster
Add entering and exiting animations for state changes
Use { borderCurve: 'continuous' } for rounded corners unless creating a capsule shape
ALWAYS use a navigation stack title instead of a custom text element on the page
When padding a ScrollView, use contentContainerStyle padding and gap instead of padding on the ScrollView itself (reduces clipping)
CSS and Tailwind are not supported - use inline styles

Colors

Use the Color API from expo-router for native semantic colors. It is a type-safe wrapper over PlatformColor that exposes iOS UIKit colors through Color.ios.* and Android Material 3 colors through Color.android.material.* (static) or Color.android.dynamic.* (adapts to the user's wallpaper on Android 12+). These resolve on-device and automatically adapt to light/dark mode and accessibility settings, so you no longer maintain separate light/dark hex tables or a colors.web.ts file.

Color is platform-specific, so wrap each value in Platform.select with a default hex fallback for web. Centralize the palette in theme/colors.ts and import colors everywhere:

// theme/colors.ts
import { Platform } from "react-native";
import { Color } from "expo-router";

export const colors = {
  label: Platform.select({
    ios: Color.ios.label,
    android: Color.android.dynamic.onSurface,
    default: "#000000",
  })!,
  secondaryLabel: Platform.select({
    ios: Color.ios.secondaryLabel,
    android: Color.android.dynamic.onSurfaceVariant,
    default: "#3c3c43",
  })!,
  separator: Platform.select({
    ios: Color.ios.separator,
    android: Color.android.dynamic.outlineVariant,
    default: "#c6c6c8",
  })!,
  systemBackground: Platform.select({
    ios: Color.ios.systemBackground,
    android: Color.android.dynamic.surface,
    default: "#ffffff",
  })!,
  systemBlue: Platform.select({
    ios: Color.ios.systemBlue,
    android: Color.android.dynamic.primary,
    default: "#007aff",
  })!,
};

import { colors } from "@/theme/colors";

<View style={{ backgroundColor: colors.systemBackground }}>
  <Text style={{ color: colors.label }}>Title</Text>
</View>;

iOS re-resolves these colors automatically when the system theme changes. On Android, call useColorScheme() inside any component that renders them so it re-renders when the theme flips (required when React Compiler memoizes the component).
Don't pass Color / PlatformColor values into Reanimated styles — use static colors there (see references/animations.md).
Platform.select({...})! returns string | OpaqueColorValue. Most React Native style props accept ColorValue (string | OpaqueColorValue) so this works fine. But some third-party props only accept string (e.g. tintColor on expo-image). A TypeScript cast does not convert an opaque native color to a string; use a supported ColorValue prop or resolve a concrete color for string-only APIs.

Text Styling

Add the selectable prop to every <Text/> element displaying important data or error messages
Counters should use { fontVariant: 'tabular-nums' } for alignment

Shadows

Use CSS boxShadow style prop. NEVER use legacy React Native shadow or elevation styles.

<View style={{ boxShadow: "0 1px 2px rgba(0, 0, 0, 0.05)" }} />

'inset' shadows are supported.

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 in Stack.Screen options:

<Stack.Screen options={{ title: "Home" }} />

Context Menus

Add long press context menus to Link components:

import { Link } from "expo-router";

<Link href="/settings" asChild>
  <Link.Trigger>
    <Pressable>
      <Card />
    </Pressable>
  </Link.Trigger>
  <Link.Menu>
    <Link.MenuAction
      title="Share"
      icon="square.and.arrow.up"
      onPress={handleSharePress}
    />
    <Link.MenuAction
      title="Block"
      icon="nosign"
      destructive
      onPress={handleBlockPress}
    />
    <Link.Menu title="More" icon="ellipsis">
      <Link.MenuAction title="Copy" icon="doc.on.doc" onPress={() => {}} />
      <Link.MenuAction
        title="Delete"
        icon="trash"
        destructive
        onPress={() => {}}
      />
    </Link.Menu>
  </Link.Menu>
</Link>;

Link Previews

Use link previews frequently to enhance navigation:

<Link href="/settings">
  <Link.Trigger>
    <Pressable>
      <Card />
    </Pressable>
  </Link.Trigger>
  <Link.Preview />
</Link>

Link preview can be used with context menus.

Modal

Present a screen as a modal:

<Stack.Screen name="modal" options={{ presentation: "modal" }} />

Prefer this to building a custom modal component.

Sheet

Present a screen as a dynamic form sheet:

<Stack.Screen
  name="sheet"
  options={{
    presentation: "formSheet",
    sheetGrabberVisible: true,
    sheetAllowedDetents: [0.5, 1.0],
    contentStyle: { backgroundColor: "transparent" },
  }}
/>

Using contentStyle: { backgroundColor: "transparent" } makes the background liquid glass on iOS 26+.

Common route structure

A standard app layout with tabs and stacks inside each tab:

app/
  _layout.tsx — <NativeTabs />
  (index,search)/
    _layout.tsx — <Stack />
    index.tsx — Main list
    search.tsx — Search view

// app/_layout.tsx
import { NativeTabs } from "expo-router/unstable-native-tabs";
import { ThemeProvider, DarkTheme, DefaultTheme } from "expo-router/react-navigation";
import { useColorScheme } from "react-native";

export default function Layout() {
  const colorScheme = useColorScheme();
  return (
    <ThemeProvider value={colorScheme === "dark" ? DarkTheme : DefaultTheme}>
      <NativeTabs>
        <NativeTabs.Trigger name="(index)">
          <NativeTabs.Trigger.Icon sf="list.dash" md="list" />
          <NativeTabs.Trigger.Label>Items</NativeTabs.Trigger.Label>
        </NativeTabs.Trigger>
        <NativeTabs.Trigger name="(search)" role="search" />
      </NativeTabs>
    </ThemeProvider>
  );
}

Create a shared group route so both tabs can push common screens:

// app/(index,search)/_layout.tsx
import { Stack } from "expo-router/stack";
import { colors } from "@/theme/colors";

export default function Layout({ segment }) {
  const screen = segment.match(/\((.*)\)/)?.[1]!;
  const titles: Record<string, string> = { index: "Items", search: "Search" };

  return (
    <Stack
      screenOptions={{
        headerTransparent: true,
        headerShadowVisible: false,
        headerLargeTitleShadowVisible: false,
        headerLargeStyle: { backgroundColor: "transparent" },
        headerTitleStyle: { color: colors.label },
        headerLargeTitle: true,
        headerBlurEffect: "none",
        headerBackButtonDisplayMode: "minimal",
      }}
    >
      <Stack.Screen name={screen} options={{ title: titles[screen] }} />
      <Stack.Screen name="i/[id]" options={{ headerLargeTitle: false }} />
    </Stack>
  );
}

Limitations

Use this skill only when the task clearly matches its upstream product or API scope.
Verify commands, API behavior, pricing, quotas, credentials, and deployment effects against current official documentation before making changes.
Do not treat generated examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions.

Snapshot boundaries

Examples mix SDK generations and abbreviated application scaffolding. Check installed Expo/Router/React Native versions, platform support and package types before copying; hooks belong inside components or custom hooks, and omitted styles/data/components must be supplied. Respect reduced motion and transparency preferences, label interactive controls, test VoiceOver/TalkBack and keyboard focus. Obtain camera/microphone/library access at the user action and explain purpose. No module installation, native generation or publication is implicit.

building-native-ui

Expo UI Guidelines

When to Use

References