Login with Facebook SSO

• Facebook app installed and signed in — the SDK app-switches to the Facebook app, which presents the consent prompt and returns an access token to your app.
• Facebook app installed but signed out — the prompt invites the person to sign in to the Facebook app first, then returns to the login flow.
• No compatible Facebook app installed — the SDK shows a built-in fallback dialog that completes login through a Chrome Custom Tab, instead of failing.

1. Your app creates the SSO entry point early in its lifecycle and calls it with the permissions you want to request.
2. The SDK checks login state first. If the person is already logged in to your app through Facebook Login, nothing is shown.
3. Otherwise the SDK launches the consent experience:
   • App-switch path — control transfers to the installed Facebook app, which renders the consent prompt. On confirm, the Facebook app performs the OAuth exchange and returns the result.
   • Fallback path — if no compatible Facebook app is present, the SDK presents its own bundled dialog, and Continue completes login through a Chrome Custom Tab.
4. The result — an access token and granted permissions, or a cancel or error — comes back through the standard Facebook Login result handling you already use. There is no special result parsing.

1. Configure Facebook Login as usual. Set your app ID and client token, initialize the SDK, and confirm a normal Facebook Login works first.
2. Register your Android key hash. Your app’s key hash and package name must be registered for your Facebook app ID. The Facebook app validates the calling app’s signing key against the registered hashes, and rejects SSO if it does not match.
3. Update the SDK to Android 18.3.0 or later, or Unity 18.1.0 or later.
4. Test both paths — on a device or emulator with the Facebook app installed and signed in for the app-switch experience, and without it to verify the fallback dialog.

dependencies {
    implementation 'com.facebook.android:facebook-login:[18.3.0,19)'
    // facebook-common is pulled in transitively
}

<queries>
    <package android:name="com.facebook.katana" />
</queries>

import androidx.fragment.app.FragmentActivity
import com.facebook.FacebookCallback
import com.facebook.FacebookException
import com.facebook.login.FBLoginSSOLauncher
import com.facebook.login.LoginResult

class MainActivity : FragmentActivity() {

    private lateinit var ssoLauncher: FBLoginSSOLauncher

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        // Must be created in onCreate() - it registers an activity-result launcher.
        ssoLauncher = FBLoginSSOLauncher(
            this,
            object : FacebookCallback<LoginResult> {
                override fun onSuccess(result: LoginResult) {
                    val token = result.accessToken
                }
                override fun onCancel() {
                    // The person dismissed the SSO prompt.
                }
                override fun onError(error: FacebookException) {
                    // Login failed.
                }
            }
        )

        if (savedInstanceState == null) {
            val launched = ssoLauncher.launch(listOf("public_profile", "email"))
            if (!launched) {
                // No app on the device can handle the SSO intent.
                // Fall back to standard Facebook Login.
            }
        }
    }
}

FBLoginSSOLauncher(
    activity: ComponentActivity,
    callback: FacebookCallback<LoginResult>? = null,
    showWithoutFBApp: Boolean = true
)

fun launch(permissions: Collection<String> = emptyList()): Boolean

FB.Mobile.LoginWithSSO(
    IEnumerable<string> permissions = null,
    FacebookDelegate<ILoginResult> callback = null);

using System.Collections.Generic;
using Facebook.Unity;

public void SignIn()
{
#if UNITY_ANDROID
    FB.Mobile.LoginWithSSO(new List<string> { "public_profile", "email" }, OnLogin);
#else
    FB.LogInWithReadPermissions(new List<string> { "public_profile", "email" }, OnLogin);
#endif
}

void OnLogin(ILoginResult result)
{
    if (!string.IsNullOrEmpty(result.Error)) { Debug.LogError(result.Error); return; }
    if (result.Cancelled) { return; }

    if (FB.IsLoggedIn)
    {
        var token = AccessToken.CurrentAccessToken;
    }
}

• The flow doesn’t switch to the Facebook app. The Facebook app probably isn’t installed, so you get the fallback dialog instead. On native Android, a false return from launch() means the flow did not start at all.
• Login is rejected immediately. Confirm your app’s Android key hash and package are registered for your Facebook app ID — the Facebook app validates the calling app’s signature.
• No prompt appears. The person may already be logged in through Facebook Login, in which case nothing is shown by design. The Facebook app on the device may also be too old to support SSO.
• Android 11 and above can’t find the Facebook app. Make sure <package android:name="com.facebook.katana" /> is in your manifest <queries> block.
• Inspect logs. Filter Android logcat to com.facebook to see the SDK’s diagnostics.

• Facebook Login for Android
• Permissions with Facebook Login
• Access Tokens and Profiles
• Troubleshoot Facebook Login for Android
• Facebook Login with FedCM