Universal Google Sign-In

Overview

Universal Integration for Google Sign-In gives you a single, platform-agnostic API for Google authentication in Unity. It handles the fiddly, per-platform OAuth flows under the hood:

• Android via native Google Play Services,
• iOS via ASWebAuthenticationSession + deep link,
• macOS / UWP via system browser + deep link,
• Windows / Editor via a loopback HTTP server,
• WebGL via a JavaScript OAuth 2.0 implicit flow.

You write one Init + SignIn flow. The plugin routes to the right code path per platform.

Supported platforms

Platform	Flow	Client ID type
Android	Google Play Services native	Web Client ID (Android ID auto-detected)
iOS	ASWebAuthenticationSession + Deep Link	iOS Client ID
macOS	System browser + Deep Link	iOS Client ID
UWP	System browser + Deep Link	iOS Client ID
Windows / Editor	Loopback HTTP server	Desktop Client ID
WebGL	OAuth 2.0 implicit flow	Web Client ID

Requirements

• Unity 2020.3 LTS or newer
• A project registered in Google Cloud Console with the right client IDs (see below)
• For Android: Google Play Services on the test device

Google Cloud setup

Create the OAuth consent screen

1. Open console.cloud.google.com.
2. Create a project and open APIs & Services → OAuth consent screen.
3. Fill in app name, support email, and authorised domains. For testing, add your Gmail as a test user.

Create client IDs

Go to APIs & Services → Credentials → Create credentials → OAuth client ID and create:

• Web Client ID — required for Android, WebGL.
• iOS Client ID — required for iOS, macOS, UWP. Note the auto-generated URL scheme (com.googleusercontent.apps.<number>).
• Android Client ID — required for Android. Provide your package name and SHA-1 fingerprint (keytool -list -v -keystore <your.keystore>).
• Desktop Client ID — required for Windows / Editor. Note the client secret.

Keep the Web Client ID handy — it's what you pass to Unity on most platforms, even Android. Google Play Services resolves the Android Client ID automatically at runtime.

Installation

Import Universal Google Sign-In from the Unity Asset Store, or add via Package Manager → Git URL:

https://github.com/simple-yet-efficient/google-sign-in.git

Per-platform configuration

WebGL

UniversalGSignIn.Init("YOUR_WEB_CLIENT_ID", OnInit);

In Google Cloud Console, set Authorized JavaScript origins and Authorized redirect URIs to the domain that will host your build.

Android

UniversalGSignIn.Init("YOUR_WEB_CLIENT_ID", OnInit);

Do not pass the Android client ID to Unity. Google Play Services picks it up from the keystore signature at runtime.

iOS / macOS / UWP

UniversalGSignIn.Init(
    "YOUR_IOS_CLIENT_ID",
    OnInit,
    urlScheme: "com.googleusercontent.apps.XXXXXX-YYYYYY"
);

Follow Unity's deep linking guide to add the scheme to your Info.plist / Package.appxmanifest.

Windows / Editor

UniversalGSignIn.Init(
    "YOUR_DESKTOP_CLIENT_ID",
    OnInit,
    clientSecret: "YOUR_CLIENT_SECRET",
    loopbackLink: "http://localhost:3000"
);

The clientSecret is only required if you need a refresh token (offline access). For interactive-only flows, omit it.

Usage

Sign in

void OnInit(bool ready) {
    if (!ready) return;
    UniversalGSignIn.SignIn(OnSignIn);
}

void OnSignIn(UniversalGSignIn.GoogleUser user) {
    if (!string.IsNullOrEmpty(user.error)) {
        Debug.LogError($"Sign-In failed: {user.error}");
        return;
    }

    var profile = user.basicProfile;
    Debug.Log($"Hello, {profile.name} <{profile.email}>");
}

Offline access (refresh tokens)

UniversalGSignIn.GrantOfflineAccess(onGranted: refreshToken => {
    // Send this to your backend to mint short-lived access tokens later.
    PlayerPrefs.SetString("google_refresh", refreshToken);
});

Sign out

UniversalGSignIn.SignOut();
bool signedIn = UniversalGSignIn.IsSignedIn();

Silent sign-in on startup

void Start() {
    UniversalGSignIn.Init(CLIENT_ID, ready => {
        if (ready && UniversalGSignIn.IsSignedIn()) {
            var profile = UniversalGSignIn.GetCurrentUserBasicProfile();
            ShowHome(profile);
        } else {
            ShowLoginButton();
        }
    });
}

Error handling

Every callback carries an error string. Always check it before using the result:

void OnSignIn(UniversalGSignIn.GoogleUser user) {
    if (!string.IsNullOrEmpty(user.error)) {
        // User cancelled, network offline, or config mismatch.
        return;
    }
    // Success — user.idToken can be sent to your backend.
}

Troubleshooting

Error	Likely cause	Fix
INVALID_SCHEME on iOS	URL scheme not in Info.plist	Add scheme via Unity's deep-link UI
OAUTH2_CONFIG_ERROR on Android	SHA-1 mismatch in Cloud Console	Regenerate with the keystore you'll actually ship with
REDIRECT_URI_MISMATCH on Windows	Port conflict	Change loopbackLink to a free port
Sign-in returns empty user on WebGL	Origin not whitelisted	Add your domain under Authorized JavaScript origins

Support

• Issues: github.com/simple-yet-efficient/google-sign-in/issues
• Email: mohelm97@gmail.com

The plugin is covered by the Unity Asset Store Standard EULA.