expo-dev-client

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# Expo Dev Client

## Overview

A custom development client is a debug build of your app that includes your specific native modules and configuration. It replaces Expo Go when you need native code that Expo Go does not bundle.

**Core principle:** Use Expo Go for rapid prototyping. Switch to a dev client when you need custom native code, and use EAS Build to create and distribute it.

## When to Use

Use a dev client when your app requires:

- **Custom native modules** not included in Expo Go (e.g., Bluetooth, NFC, custom camera pipelines)
- **Apple ecosystem integration** (HealthKit, HomeKit, CarPlay, App Clips)
- **Third-party native SDKs** (Stripe native, Mapbox, Firebase Analytics with custom config)
- **Custom native configuration** (specific entitlements, background modes, custom URL schemes)
- **Config plugins** that modify native project files
- **Expo Modules API** for writing your own native modules

### When NOT to Use

- App only uses libraries included in Expo Go (check the Expo SDK docs)
- Quick prototyping or demo purposes (stick with Expo Go)
- Web-only features

## Expo Go vs Dev Client

| Feature | Expo Go | Dev Client |
|---------|---------|------------|
| Native code | Pre-bundled only | Any native module |
| Setup time | Zero | Requires build step |
| OTA updates | Yes | Yes |
| Custom config plugins | No | Yes |
| App Store distribution | No | Yes (via TestFlight) |
| Custom app icon/splash | No | Yes |
| Background modes | Limited | Full control |
| Fast Refresh | Yes | Yes |

## Setup

### 1. Install the Dev Client Package

```bash
npx expo install expo-dev-client
```

This adds the development client UI (launcher, error overlay, dev menu) to your app.

### 2. Configure EAS Build

```bash
# Install EAS CLI if needed
npm install -g eas-cli

# Initialize EAS in your project
eas build:configure
```

This creates `eas.json`:

```json
{
  "cli": {
    "version": ">= 5.0.0"
  },
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal",
      "ios": {
        "simulator": true
      }
    },
    "preview": {
      "distribution": "internal"
    },
    "production": {}
  }
}
```

### 3. Build the Dev Client

```bash
# iOS Simulator build
eas build --platform ios --profile development

# iOS device build (requires Apple Developer account)
eas build --platform ios --profile development \
  --local  # Optional: build locally instead of EAS servers

# Android build
eas build --platform android --profile development
```

### 4. Install and Run

```bash
# Install on simulator/emulator (automatic after build)
eas build:run --platform ios

# Or start dev server pointing to the dev client
npx expo start --dev-client
```

## Distribution

### Internal Distribution (Testing)

For sharing dev builds with your team:

```json
// eas.json
{
  "build": {
    "development": {
      "developmentClient": true,
      "distribution": "internal"
    }

From bidah/react-native-hifi, MIT.

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