google oauth mobile app

If you want Google OAuth for a mobile app, the usual setup is:

Recommended approach

Use OAuth 2.0 Authorization Code flow with PKCE.

This is the standard secure flow for mobile apps because:

• you don’t store a client secret in the app
• it works with Google sign-in
• it supports Android and iOS properly

High-level flow

1. User taps Sign in with Google
2. App opens the Google authorization screen in the system browser / custom tab / ASWebAuthenticationSession
3. User logs in and approves permissions
4. Google redirects back to your app using a redirect URI
5. App receives an authorization code
6. App exchanges the code for tokens using PKCE
7. App uses the access token to call Google APIs, and/or sends the ID token to your backend

What you need to set up

1. Create OAuth credentials in Google Cloud Console

• Create a project
• Enable needed APIs
• Configure the OAuth consent screen
• Create OAuth client IDs for:
  • Android
  • iOS
  • optionally Web if you have a backend

2. Configure redirect URI

For mobile apps, redirect URIs are usually:

• Android App Links or custom scheme
• iOS Universal Links or custom scheme
• or a backend redirect that forwards to the app

3. Use PKCE

Your app generates:

• code_verifier
• code_challenge

Google returns an auth code, then you exchange it with the verifier.

Tokens you may get

• Authorization code: short-lived, one-time use
• Access token: used to call Google APIs
• ID token: identifies the user
• Refresh token: may be issued depending on config and offline access

Important mobile app note

Avoid:

• embedded webviews for login, if possible

Use:

• Android: Chrome Custom Tabs
• iOS: ASWebAuthenticationSession

These are the recommended secure browser-based login methods.

If you want Google login only

You often just need:

• Google Sign-In SDK for Android/iOS
• ID token
• backend verification if you have a server

Example libraries

• Android: Google Identity Services / Google Sign-In
• iOS: Google Sign-In SDK
• React Native / Flutter / Xamarin / etc.: platform wrappers or browser-based OAuth libraries

If you want, I can give you:

1. Android implementation
2. iOS implementation
3. Flutter example
4. React Native example
5. backend token verification example