How do I add Google and Apple sign in to a mobile app?

To add Google and Apple sign-in to a mobile app, the usual approach is to use OAuth / OpenID Connect through each provider’s SDKs, then send the resulting identity token or authorization code to your backend to create or link a user in your system.

High-level flow

1. User taps “Sign in with Google” or “Sign in with Apple.”
2. The provider shows a login/consent screen.
3. The app receives an ID token or authorization code.
4. Your app sends that token/code to your backend.
5. Your backend verifies it with Google/Apple.
6. Your backend creates or logs in the user and returns your own session token (JWT, cookie, etc.).

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Google Sign-In

Mobile app

• Use Google’s sign-in SDK:
  • Android: Google Identity Services / Google Sign-In
  • iOS: GoogleSignIn SDK
  • Cross-platform: Flutter, React Native, and others have wrappers

Backend

• Verify the ID token with Google.
• Check:
  • issuer (iss)
  • audience (aud) matches your client ID
  • expiry (exp)
  • subject (sub) as the stable Google user ID

Typical libraries

• Android/iOS: Google Sign-In SDK
• Node.js: google-auth-library
• Python: google-auth
• Java: Google token verifier libraries

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Apple Sign-In

Mobile app

• Use Sign in with Apple:
  • iOS: AuthenticationServices framework
  • For Android/web fallback: Apple’s web-based OAuth flow

Backend

• Verify the Apple identity token (JWT) using Apple’s public keys.
• Also validate:
  • iss = https://appleid.apple.com
  • aud = your app’s client ID / Service ID
  • exp
  • sub

Important Apple note

• Apple only gives the user’s name and email the first time they authorize, so save them immediately.
• You may need a Service ID and private key if you’re doing server-side code exchange.

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What you should implement in your app/backend

1) Create provider credentials

Google

• Create a project in Google Cloud Console
• Configure:
  • OAuth consent screen
  • Android client ID
  • iOS client ID
  • Web client ID (often needed for backend verification)

Apple

• Join the Apple Developer Program
• Enable Sign in with Apple
• Create:
  • App ID / Bundle ID capability
  • Service ID (if needed for web/server flows)
  • Key for generating client secrets

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2) Add sign-in buttons

• Place:
  • Continue with Google
  • Sign in with Apple
• Follow provider branding guidelines:
  • Apple has strict button styling rules
  • Google has branding requirements too

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3) Authenticate with the provider SDK

• Launch the provider sign-in flow.
• Receive:
  • Google: ID token, sometimes auth code
  • Apple: identity token, authorization code

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4) Send token to backend

Example payload:

{
  "provider": "google",
  "idToken": "eyJhbGciOi..."
}

or

{
  "provider": "apple",
  "identityToken": "eyJhbGciOi..."
}

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5) Verify on backend

Your backend should:

• validate signature
• validate audience
• validate expiry
• extract provider user ID
• map it to your internal user account

Then issue your app’s own auth token.

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Security best practices

• Never trust tokens just because they came from the app
• Verify tokens on the server
• Use HTTPS everywhere
• Store only the minimum needed user data
• Link multiple providers to one account if the emails match or the user explicitly links them
• Use refresh/session tokens for your own backend, not provider tokens as your app session

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Platform-specific notes

iOS

• Apple Sign-In is strongly recommended if you offer third-party sign-in and your app is distributed on the App Store.
• If you offer Google/Facebook/etc., Apple often requires Sign in with Apple too.

Android

• Google Sign-In is straightforward.
• Apple Sign-In is less common but can be supported through the web flow.

Cross-platform

• Flutter:
  • google_sign_in
  • sign_in_with_apple
• React Native:
  • @react-native-google-signin/google-signin
  • @invertase/react-native-apple-authentication

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If you want the shortest implementation path

Use:

• Provider SDK in the app
• Backend token verification
• Your own JWT/session system

That’s the standard production setup.

If you want, I can give you:

1. a step-by-step iOS/Android implementation,
2. a Flutter example, or
3. a Node.js backend example for verifying Google and Apple tokens.