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FBLoginButton is a UIButton subclass that automatically manages the login and logout flow. When the user is logged out it shows “Continue with Facebook”; when they are logged in it shows “Log out” and presents a confirmation sheet before clearing the session. You do not need to add any tap targets — the button handles everything internally.

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Add the button programmatically

import FacebookLogin

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let loginButton = FBLoginButton()
        loginButton.permissions = ["public_profile", "email"]
        loginButton.delegate = self
        loginButton.center = view.center
        view.addSubview(loginButton)
    }
}

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Add the button in Interface Builder

1

Add a UIButton

Drag a Button from the Object Library onto your view.
2

Set the custom class

In the Identity Inspector, set Class to FBLoginButton and Module to FBSDKLoginKit.
3

Connect the delegate outlet

Control-drag from the button to your view controller and connect it to the delegate @IBOutlet.
4

Set permissions in code

In viewDidLoad, set the permissions property on the connected outlet.
@IBOutlet weak var loginButton: FBLoginButton!

override func viewDidLoad() {
    super.viewDidLoad()
    loginButton.permissions = ["public_profile", "email"]
}

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Set permissions

Assign permission strings to the permissions property before the button appears on screen: 
loginButton.permissions = ["public_profile", "email", "user_friends"]
The button’s fixed height is 28 points. Its width adjusts to fit the label text.

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Configure login tracking

Set loginTracking to switch between standard and Limited Login: 
// Standard login (default)
loginButton.loginTracking = .enabled

// Limited Login (iOS 14+)
loginButton.loginTracking = .limited

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Configure a nonce

For OIDC replay protection you can supply a custom nonce. The value must be a non-empty string without whitespace; invalid values are silently ignored and a UUID is used instead: 
loginButton.nonce = "my-server-generated-nonce"

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Implement LoginButtonDelegate

Conform to LoginButtonDelegate to react to login and logout events: 
extension ViewController: LoginButtonDelegate {

    func loginButton(
        _ loginButton: FBLoginButton,
        didCompleteWith result: LoginManagerLoginResult?,
        error: Error?
    ) {
        if let error = error {
            print("Login error: \(error)")
            return
        }

        guard let result = result else { return }

        if result.isCancelled {
            print("User cancelled login")
        } else {
            print("Logged in. Granted: \(result.grantedPermissions)")
            if let token = result.token {
                print("Token: \(token.tokenString)")
            }
        }
    }

    func loginButtonDidLogOut(_ loginButton: FBLoginButton) {
        print("User logged out")
        // Update your UI
    }

    // Optional: return false to prevent the login attempt
    func loginButtonWillLogin(_ loginButton: FBLoginButton) -> Bool {
        return true
    }
}
The delegate methods map to three distinct moments:
MethodWhen it fires
loginButtonWillLogin(_:)Just before the login UI appears. Return false to abort.
loginButton(_:didCompleteWith:error:)After the login attempt completes (success, cancel, or error).
loginButtonDidLogOut(_:)After the user confirms logout.

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Tooltip behavior

The button can show an onboarding tooltip the first time it appears. You can control this with tooltipBehavior: 
loginButton.tooltipBehavior = .automatic   // Show if eligible (default)
loginButton.tooltipBehavior = .forceDisplay // Always show (useful for testing)
loginButton.tooltipBehavior = .disable     // Never show

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Default audience

If you request publish permissions, set defaultAudience to control the initial sharing scope: 
loginButton.defaultAudience = .friends  // Default
loginButton.defaultAudience = .onlyMe
loginButton.defaultAudience = .everyone

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