capacitor-expert

Capacitor Expert

Comprehensive reference for building cross-platform apps with Capacitor. Covers architecture, CLI, plugins, framework integration, best practices, and Capawesome Cloud.

Core Concepts

Capacitor is a cross-platform native runtime for building web apps that run natively on iOS, Android, and the web. The web app runs in a native WebView, and Capacitor provides a bridge to native APIs via plugins.

Architecture

A Capacitor app has three layers:

1. Web layer -- HTML/CSS/JS app running inside a native WebView (WKWebView on iOS, Android System WebView on Android).
2. Native bridge -- Serializes JS plugin calls, routes them to native code, and returns results as Promises.
3. Native layer -- Swift/ObjC (iOS) and Kotlin/Java (Android) code implementing native functionality.

Data passed across the bridge must be JSON-serializable. Pass files as paths, not base64.

Project Structure

my-app/
  android/                  # Native Android project (committed to VCS)
  ios/                      # Native iOS project (committed to VCS)
    App/
      App/                  # iOS app source files
      App.xcodeproj/
  src/                      # Web app source code
  dist/ or www/ or build/   # Built web assets
  capacitor.config.ts       # Capacitor configuration
  package.json

The android/ and ios/ directories are full native projects -- they are committed to version control and can be modified directly.

Capacitor Config

capacitor.config.ts (preferred) or capacitor.config.json controls app behavior:

import type { CapacitorConfig } from '@capacitor/cli';

const config: CapacitorConfig = {
  appId: 'com.example.app',
  appName: 'My App',
  webDir: 'dist',
  server: {
    // androidScheme: 'https', // default in Cap 6+
  },
};

export default config;

For details, see App Configuration.

Creating a New App

Quick Start

# 1. Create a web app (React example with Vite)
npm create vite@latest my-app -- --template react-ts
cd my-app && npm install

# 2. Install Capacitor
npm install @capacitor/core
npm install -D @capacitor/cli

# 3. Initialize Capacitor
npx cap init "My App" com.example.myapp --web-dir dist

# 4. Build web assets
npm run build

# 5. Add platforms
npm install @capacitor/android @capacitor/ios
npx cap add android
npx cap add ios

# 6. Sync and run
npx cap sync
npx cap run android
npx cap run ios

Web asset directories by framework:

• Angular: dist/<project-name>/browser (Angular 17+ with application builder)
• React (Vite): dist
• Vue (Vite): dist
• Vanilla: www

For the full guided creation flow, see capacitor-app-creation.

Capacitor CLI

All commands: npx cap <command>. Most important commands:

For the full CLI reference, see CLI Reference.

Framework Integration

Capacitor works with any web framework. Framework-specific patterns:

Angular

• Wrap Capacitor plugins in Angular services for DI and testability.
• Plugin event listeners run outside NgZone -- always wrap callbacks in NgZone.run().
• Register listeners in ngOnInit, remove in ngOnDestroy.

For details, see capacitor-angular.

React

• Create custom hooks (useCamera, useNetwork) that wrap Capacitor plugins.
• Use useEffect for listener registration with cleanup to prevent memory leaks.
• React 18 strict mode double-mounts -- ensure cleanup functions work correctly.

For details, see capacitor-react.

Vue

• Create composables (useCamera, useNetwork) using Vue 3 Composition API.
• Register listeners in onMounted, remove in onUnmounted.
• Vue reactivity picks up ref changes automatically (no NgZone equivalent needed).

For details, see capacitor-vue.

Plugins

Plugins are Capacitor's extension mechanism. Each plugin exposes a JS API backed by native implementations.

Plugin Sources

• Official (@capacitor/*) -- Camera, Filesystem, Geolocation, Preferences, etc.
• Capawesome (@capawesome/*, @capawesome-team/*) -- SQLite, NFC, Biometrics, Live Update, etc.
• Community (@capacitor-community/*) -- AdMob, BLE, SQLite, Stripe, etc.
• Firebase (@capacitor-firebase/*) -- Analytics, Auth, Messaging, Firestore, etc.
• MLKit (@capacitor-mlkit/*) -- Barcode scanning, face detection, translation.
• RevenueCat (@revenuecat/purchases-capacitor) -- In-app purchases.

Installing a Plugin

npm install @capacitor/camera
npx cap sync

After installation, apply any required platform configuration (permissions in AndroidManifest.xml, Info.plist entries, etc.) as documented by the plugin.

Using a Plugin

import { Camera, CameraResultType } from '@capacitor/camera';

const photo = await Camera.getPhoto({
  quality: 90,
  resultType: CameraResultType.Uri,
});

For the full plugin index (160+ plugins) and setup guides, see capacitor-plugins.

Plugin Development

Create custom Capacitor plugins with native iOS (Swift) and Android (Java/Kotlin) implementations:

1. Scaffold with npm init @capacitor/plugin@latest.
2. Define the TypeScript API in src/definitions.ts.
3. Implement the web layer in src/web.ts.
4. Implement iOS plugin in ios/Sources/.
5. Implement Android plugin in android/src/main/java/.
6. Verify with npm run verify.

Key rules:

• The registerPlugin() name in src/index.ts must match jsName on iOS and @CapacitorPlugin(name = "...") on Android.
• iOS methods need @objc and must be listed in pluginMethods (CAPBridgedPlugin).
• Android methods need @PluginMethod() annotation and must be public.

For full details, see capacitor-plugin-development.

Cross-Platform Best Practices

Platform Detection

import { Capacitor } from '@capacitor/core';

const platform = Capacitor.getPlatform(); // 'android' | 'ios' | 'web'
if (Capacitor.isNativePlatform()) { /* native-only code */ }
if (Capacitor.isPluginAvailable('Camera')) { /* plugin available */ }

Permissions

Follow the check-then-request pattern:

const status = await Camera.checkPermissions();
if (status.camera !== 'granted') {
  const requested = await Camera.requestPermissions();
  if (requested.camera === 'denied') {
    // Guide user to app settings -- cannot re-request on iOS
    return;
  }
}
const photo = await Camera.getPhoto({ ... });

Performance

• Minimize bridge calls -- batch operations instead of many individual calls.
• Use file paths over base64 for binary data.
• Lazy-load plugins with dynamic imports for code splitting.

Error Handling

Always wrap plugin calls in try-catch:

try {
  const photo = await Camera.getPhoto({ resultType: CameraResultType.Uri });
} catch (error) {
  if (error.message === 'User cancelled photos app') {
    // Not an error
  } else {
    console.error('Camera error:', error);
  }
}

For full details, see Cross-Platform Best Practices.

Deep Links

Deep links open specific content in the app from external URLs.

• iOS: Universal Links via apple-app-site-association hosted at https://<domain>/.well-known/.
• Android: App Links via assetlinks.json hosted at https://<domain>/.well-known/.

Listener Setup

import { App } from '@capacitor/app';

App.addListener('appUrlOpen', (event) => {
  const path = new URL(event.url).pathname;
  // Route to the appropriate page
});

Platform Configuration

• iOS: Add applinks:<domain> to Associated Domains capability in ios/App/App/App.entitlements.
• Android: Add <intent-filter android:autoVerify="true"> to android/app/src/main/AndroidManifest.xml.

For full setup, see Deep Links.

Storage

Do NOT use localStorage, IndexedDB, or cookies for persistent data -- the OS can evict them (especially on iOS).

For details, see Storage.

Security

• Never embed secrets (API keys with write access, OAuth secrets, DB credentials) in client code -- move to a server API.
• Use secure storage (@capawesome-team/capacitor-secure-preferences) for tokens and credentials, not localStorage or @capacitor/preferences.
• HTTPS only -- never allow cleartext HTTP in production.
• Content Security Policy -- add a <meta> CSP tag in index.html.
• Disable WebView debugging in production: set webContentsDebuggingEnabled: false in capacitor.config.ts.
• Prefer Universal/App Links over custom URL schemes (verified via HTTPS).
• iOS Privacy Manifest (PrivacyInfo.xcprivacy) -- required for iOS 17+ when using privacy-sensitive APIs.

For details, see Security.

Testing

Unit Testing

Mock Capacitor plugins in Jest/Vitest since tests run in Node.js, not a WebView:

vi.mock('@capacitor/camera', () => ({
  Camera: {
    getPhoto: vi.fn().mockResolvedValue({
      webPath: 'https://example.com/photo.jpg',
    }),
  },
}));

E2E Testing

• Web E2E: Cypress or Playwright (tests web layer, plugins must be mocked).
• Native E2E: Appium (cross-platform) or Detox (iOS-focused).

Debugging

• Android: Enable webContentsDebuggingEnabled: true, open chrome://inspect in Chrome.
• iOS: Enable webContentsDebuggingEnabled: true, use Safari > Develop menu > select device.

For details, see Testing.

Troubleshooting

Android

• npx cap sync fails: Verify @capacitor/core and @capacitor/cli versions match. Run cd android && ./gradlew clean.
• Build fails after config changes: Clean with cd android && ./gradlew clean, then rebuild.
• Plugin not found at runtime: Run npx cap sync after plugin installation. Verify Gradle sync completed.
• SDK errors: Verify ANDROID_HOME is set. Install missing SDK versions via Android Studio SDK Manager.
• White square notification icon: Push notification icons must be white pixels on transparent background.

iOS

• Build fails with "no such module": Run npx cap sync ios. For CocoaPods: cd ios/App && pod install --repo-update.
• Build fails after config changes: Clean build folder (Xcode Product > Clean Build Folder) or delete ios/App/Pods and re-run pod install.
• Simulator cannot receive push notifications: Use a physical device for push notification testing.
• Permission denied permanently: Cannot re-request on iOS. Guide user to Settings > App > Permissions.
• WebView not loading: Verify webDir in capacitor.config.ts matches the actual build output directory.

General

• Live reload not connecting: Ensure device and dev machine are on the same network. Use --external flag.
• Plugin not found: Run npx cap sync. Verify plugin is in package.json dependencies.
• Capacitor is not defined: Install @capacitor/core (npm install @capacitor/core).

For full troubleshooting, see Android Troubleshooting and iOS Troubleshooting.

Upgrading

Capacitor supports upgrades across major versions (4 through 8). Apply each major version jump sequentially -- do not skip intermediate versions.

Do not run npx cap migrate. It is an interactive command that cannot be invoked by an agent. Apply all upgrade steps manually using the per-version reference files.

For app upgrades, see capacitor-app-upgrades. For plugin upgrades, see capacitor-plugin-upgrades.

Capawesome Cloud

Capawesome Cloud provides cloud infrastructure for Capacitor apps: native builds, live updates, and automated app store publishing.

Website: capawesome.io | Cloud Services: capawesome.io/cloud/

Getting Started

# Install and authenticate
npx @capawesome/cli login

# Create an app
npx @capawesome/cli apps:create

Live Updates

Deploy over-the-air (OTA) web updates to Capacitor apps without going through the app stores. Users receive updates immediately on next app launch.

Setup:

# Install the live update plugin
npm install @capawesome/capacitor-live-update
npx cap sync

Configure in capacitor.config.ts:

const config: CapacitorConfig = {
  plugins: {
    LiveUpdate: {
      appId: '<APP_ID>',
      autoUpdate: true,
    },
  },
};

Deploy an update:

npm run build
npx @capawesome/cli apps:liveupdates:upload --app-id <APP_ID>

Native Builds

Build iOS and Android apps in the cloud without local build environments. Supports signing certificates, environments, and build configuration.

# Trigger a build
npx @capawesome/cli apps:builds:create --app-id <APP_ID> --platform android

# Download the artifact
npx @capawesome/cli apps:builds:download --app-id <APP_ID> --build-id <BUILD_ID>

App Store Publishing

Automate submissions to Apple App Store (TestFlight) and Google Play Store.

# Create a deployment destination
npx @capawesome/cli apps:destinations:create --app-id <APP_ID>

# Deploy a build
npx @capawesome/cli apps:deployments:create --app-id <APP_ID> --build-id <BUILD_ID>

CI/CD Integration

Use token-based auth for CI/CD pipelines:

npx @capawesome/cli login --token <TOKEN>
npx @capawesome/cli apps:builds:create --app-id <APP_ID> --platform ios --detached

For full Capawesome Cloud setup, see capawesome-cloud. For the Capawesome CLI reference, see capawesome-cli.

Push Notifications

Set up push notifications using Firebase Cloud Messaging (FCM) via @capacitor-firebase/messaging:

npm install @capacitor-firebase/messaging firebase
npx cap sync

Requires Firebase project setup, platform-specific configuration (APNs for iOS, google-services.json for Android), and permission handling.

For the full setup guide, see capacitor-push-notifications.

In-App Purchases

Set up in-app purchases and subscriptions with either:

• Capawesome Purchases (@capawesome-team/capacitor-purchases) -- lightweight, no third-party backend, requires Capawesome Insiders license.
• RevenueCat (@revenuecat/purchases-capacitor) -- full managed backend with receipt validation, analytics, and integrations.

Both require App Store Connect (iOS) and/or Google Play Console (Android) product configuration.

For the full setup guide, see capacitor-in-app-purchases.

Related Skills

• capacitor-app-creation -- Create a new Capacitor app from scratch.
• capacitor-app-development -- General Capacitor development topics, configuration, and troubleshooting.
• capacitor-angular -- Angular-specific Capacitor patterns.
• capacitor-react -- React-specific Capacitor patterns.
• capacitor-vue -- Vue-specific Capacitor patterns.
• capacitor-plugins -- Install and configure 160+ Capacitor plugins.
• capacitor-plugin-development -- Create custom Capacitor plugins.
• capacitor-app-upgrades -- Upgrade Capacitor apps across major versions.
• capacitor-plugin-upgrades -- Upgrade Capacitor plugins across major versions.
• capacitor-push-notifications -- Push notifications with FCM.
• capacitor-in-app-purchases -- In-app purchases and subscriptions.
• capawesome-cloud -- Live updates, native builds, app store publishing.
• capawesome-cli -- Capawesome CLI reference.