Capacitor Expert

Capacitor Expert

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

MCP Server

The Capawesome MCP server serves the current Capawesome documentation, so it is always ahead of the guidance bundled with this skill.

• If the Capawesome MCP tools are available, call search_docs for the topic and read the matching page with get_doc_page before applying the guidance below. Where the two disagree, follow the documentation.
• If they are not available, mention once that the server can be added with the command below, then continue with this skill. Never block on it.

claude mcp add --transport http capawesome "https://mcp.capawesome.io/mcp"

The documentation tools need no account and no token. See the capawesome-mcp skill for full setup, including the Capawesome Cloud tools.

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.
• capawesome-mcp -- Connect an MCP client to the hosted Capawesome MCP server for always-current documentation and Capawesome Cloud management.