/mobile-navigation-expo-router

name: mobile-navigation-expo-router
description: File-based routing and navigation for Expo/React Native

Expo Router Patterns

> **Quick Guide:** File-based routing for React Native and web. Files in `app/` become routes automatically. Use `_layout.tsx` for navigation structure (Stack, Tabs), groups `(name)/` for URL-invisible organization, `[param]` for dynamic segments. SDK 53+: use `Stack.Protected` with a `guard` prop for authentication. Enable `typedRoutes` for compile-time route safety. API routes use `+api.ts` suffix.

---

<critical_requirements>

CRITICAL: Before Using This Skill

**(You MUST define navigation structure in `_layout.tsx` files -- screens without a layout parent default to a basic Stack)**

**(You MUST use `Stack.Protected` with `guard` prop for authentication flows in SDK 53+ -- NOT imperative redirects in useEffect)**

**(You MUST use `useLocalSearchParams` for route params in screens -- `useGlobalSearchParams` causes unnecessary re-renders on unfocused screens)**

**(You MUST enable `typedRoutes` in app.json experiments for compile-time route validation -- catches invalid navigation at build time)**

</critical_requirements>

---

**Auto-detection:** expo-router, Expo Router, file-based routing, \_layout.tsx, Stack.Screen, Tabs.Screen, useRouter, useLocalSearchParams, useSegments, usePathname, Link href, router.push, router.replace, router.dismiss, router.dismissTo, +api.ts, +not-found, Stack.Protected, generateStaticParams, expo-router/head, Slot, Redirect, useFocusEffect, NativeTabs, headless tabs, TabSlot, TabTrigger

**When to use:**

• Setting up file-based navigation in an Expo app
• Implementing authentication flows with route protection
• Creating tab, stack, or modal navigation layouts
• Building API routes for server-side logic
• Configuring typed routes for compile-time safety
• Adding deep linking and static rendering for web

**Key patterns covered:**

• File convention: `_layout.tsx`, `[param]`, `[...slug]`, `(group)/`, `+api.ts`, `+not-found.tsx`
• Layout navigators: Stack, Tabs, headless tabs, native tabs
• Authentication: `Stack.Protected` guard pattern (SDK 53+), redirect pattern (SDK 52)
• Navigation hooks: `useRouter`, `useLocalSearchParams`, `useSegments`, `usePathname`
• API routes with standard Request/Response
• Typed routes with auto-generated TypeScript definitions
• Modal routes, shared routes between tabs, nested navigation

**When NOT to use:**

• Apps that need fully custom native navigation controllers beyond what React Navigation provides
• Simple single-screen apps with no navigation
• Web-only projects where a web-native router is more appropriate

---

<philosophy>

Philosophy

Expo Router maps the filesystem to your navigation hierarchy. Every file in `app/` is a route; every `_layout.tsx` defines how its sibling routes are presented (stack, tabs, drawer). This convention-over-configuration approach means:

1. **URLs are first-class** -- every screen has a URL, enabling deep linking on mobile and SEO on web without extra configuration 2. **Layouts are composable** -- nest `_layout.tsx` files to create any navigation structure (tabs containing stacks containing modals) 3. **The file tree IS the sitemap** -- new developers understand navigation by reading the directory structure, not a central config 4. **Universal by default** -- the same route definitions work on iOS, Android, and web

**Mental model:** Think of `app/` as a website. `_layout.tsx` files are the "chrome" (nav bars, tab bars). Route files are the "pages." Groups `(name)/` organize without affecting URLs. This maps directly to how web routing works, which is intentional -- Expo Router is built on top of React Navigation but presents a web-like API.

</philosophy>

---

<patterns>

Core Patterns

Pattern 1: File Conventions

Every file in `app/` maps to a route. Special characters change behavior:

| File | URL | Purpose | | ---------------- | -------------------- | ---------------------------------------- | | `index.tsx` | `/` (or parent path) | Default route for directory | | `about.tsx` | `/about` | Static route | | `[id].tsx` | `/:id` | Dynamic segment | | `[...slug].tsx` | `/a/b/c` | Catch-all segments | | `_layout.tsx` | N/A | Wraps sibling routes in navigator | | `(group)/` | Not in URL | Organizes routes without URL impact | | `+not-found.tsx` | N/A | 404 fallback for unmatched routes | | `+api.ts` | Server endpoint | API route handler | | `+html.tsx` | N/A | Root HTML wrapper (web static rendering) |

**Key insight:** Groups `(name)/` are purely organizational. `(tabs)/home.tsx` and `home.tsx` both resolve to `/home`. Use groups to apply different layouts to different route sets without changing URLs.

> Full directory structure examples: [examples/core.md](examples/core.md)

---

Pattern 2: Layout Routes

`_layout.tsx` files wrap their sibling routes in a navigator. The layout determines HOW routes are presented (stack push, tab switch, modal overlay).

// app/_layout.tsx -- Root layout wrapping entire app
import { Stack } from "expo-router";

export default function RootLayout() {
  return (
    <Stack>
      <Stack.Screen name="(tabs)" options={{ headerShown: false }} />
      <Stack.Screen name="modal" options={{ presentation: "modal" }} />
      <Stack.Screen name="+not-found" />
    </Stack>
  );
}

**Why this matters:** Without a `_layout.tsx`, routes get a default Stack navigator with default headers. Always define layouts explicitly for control over headers, transitions, and navigation structure.

**Gotcha:** The `name` prop in `Stack.Screen`/`Tabs.Screen` must match the fi