google_sign_in 6.2.2

Flutter plugin for Google Sign-In, a secure authentication system for signing in with a Google account.

A Flutter plugin for Google Sign In.

	Android	iOS	macOS	Web
Support	SDK 16+	12.0+	10.15+	Any

Platform integration

Android integration

To access Google Sign-In, you'll need to make sure to register your application.

You don't need to include the google-services.json file in your app unless you are using Google services that require it. You do need to enable the OAuth APIs that you want, using the Google Cloud Platform API manager. For example, if you want to mimic the behavior of the Google Sign-In sample app, you'll need to enable the Google People API.

Make sure you've filled out all required fields in the console for OAuth consent screen. Otherwise, you may encounter APIException errors.

iOS integration

Please see instructions on integrating Google Sign-In for iOS.

iOS additional requirement

Note that according to https://developer.apple.com/sign-in-with-apple/get-started, starting June 30, 2020, apps that use login services must also offer a "Sign in with Apple" option when submitting to the Apple App Store.

Consider also using an Apple sign in plugin from pub.dev.

The Flutter Favorite sign_in_with_apple plugin could be an option.

macOS integration

Please see instructions on integrating Google Sign-In for macOS.

Web integration

The new SDK used by the web has fully separated Authentication from Authorization, so signIn and signInSilently no longer authorize OAuth scopes.

Flutter apps must be able to detect what scopes have been granted by their users, and if the grants are still valid.

Read below about Working with scopes, and incremental authorization for general information about changes that may be needed on an app, and for more specific web integration details, see the google_sign_in_web package.

Usage

Import the package

To use this plugin, follow the plugin installation instructions.

Use the plugin

Initialize GoogleSignIn with the scopes you want:

const List<String> scopes = <String>[
  'email',
  'https://www.googleapis.com/auth/contacts.readonly',
];

GoogleSignIn _googleSignIn = GoogleSignIn(
  // Optional clientId
  // clientId: 'your-client_id.apps.googleusercontent.com',
  scopes: scopes,
);

Full list of available scopes.

You can now use the GoogleSignIn class to authenticate in your Dart code, e.g.

Future<void> _handleSignIn() async {
  try {
    await _googleSignIn.signIn();
  } catch (error) {
    print(error);
  }
}

In the web, you should use the Google Sign In button (and not the signIn method) to guarantee that your user authentication contains a valid idToken.

For more details, take a look at the google_sign_in_web package.

Working with scopes, and incremental authorization.

If your app supports both mobile and web, read this section!

Checking if scopes have been granted

Users may (or may not) grant all the scopes that an application requests at Sign In. In fact, in the web, no scopes are granted by signIn, silentSignIn or the renderButton widget anymore.

Applications must be able to:

• Detect if the authenticated user has authorized the scopes they need.
• Determine if the scopes that were granted a few minutes ago are still valid.

There's a new method that enables the checks above, canAccessScopes:

// In mobile, being authenticated means being authorized...
bool isAuthorized = account != null;
// However, on web...
if (kIsWeb && account != null) {
  isAuthorized = await _googleSignIn.canAccessScopes(scopes);
}

(Only implemented in the web platform, from version 6.1.0 of this package)

Requesting more scopes when needed

If an app determines that the user hasn't granted the scopes it requires, it should initiate an Authorization request. (Remember that in the web platform, this request must be initiated from an user interaction, like a button press).

Future<void> _handleAuthorizeScopes() async {
  final bool isAuthorized = await _googleSignIn.requestScopes(scopes);
  if (isAuthorized) {
    unawaited(_handleGetContact(_currentUser!));
  }

The requestScopes returns a boolean value that is true if the user has granted all the requested scopes or false otherwise.

Once your app determines that the current user isAuthorized to access the services for which you need scopes, it can proceed normally.

Authorization expiration

In the web, the accessToken is no longer refreshed. It expires after 3600 seconds (one hour), so your app needs to be able to handle failed REST requests, and update its UI to prompt the user for a new Authorization round.

This can be done by combining the error responses from your REST requests with the canAccessScopes and requestScopes methods described above.

For more details, take a look at the google_sign_in_web package.

Does an app always need to check canAccessScopes?

The new web SDK implicitly grant access to the email, profile and openid scopes when users complete the sign-in process (either via the One Tap UX or the Google Sign In button).

If an app only needs an idToken, or only requests permissions to any/all of the three scopes mentioned above (OpenID Connect scopes), it won't need to implement any additional scope handling.

If an app needs any scope other than email, profile and openid, it must implement a more complete scope handling, as described above.

Example

Find the example wiring in the Google sign-in example application.