1 Enable the Capability

In Xcode, add the Sign in with Apple capability:

1. Select your target → Signing & Capabilities
2. Click "+ Capability"
3. Search for and add "Sign in with Apple"
4. This automatically configures your entitlements and provisioning profile

2 Create the Authorization Request

SwiftUI implementation:

import AuthenticationServices

struct SignInView: View {
    var body: some View {
        SignInWithAppleButton(
            onRequest: { request in
                request.requestedScopes = [.fullName, .email]
            },
            onCompletion: { result in
                switch result {
                case .success(let auth):
                    handleAuthorization(auth)
                case .failure(let error):
                    handleError(error)
                }
            }
        )
        .signInWithAppleButtonStyle(.black) // or .white, .whiteOutline
        .frame(height: 50)
    }
}

3 Handle the Authorization Response

func handleAuthorization(_ authorization: ASAuthorization) {
    guard let credential = authorization.credential
        as? ASAuthorizationAppleIDCredential else {
        return
    }

    // User identifier - ALWAYS available, never changes
    let userIdentifier = credential.user

    // Email - only provided on FIRST sign-in
    let email = credential.email

    // Name - only provided on FIRST sign-in
    let fullName = credential.fullName

    // Identity token for server verification
    if let identityToken = credential.identityToken,
       let tokenString = String(data: identityToken, encoding: .utf8) {
        // Send to your server for verification
        authenticateWithServer(
            userID: userIdentifier,
            identityToken: tokenString,
            email: email,
            name: fullName
        )
    }
}

4 Check Credential State on App Launch

Verify the user's credential is still valid:

func checkCredentialState() {
    let provider = ASAuthorizationAppleIDProvider()
    provider.getCredentialState(forUserID: savedUserID) { state, error in
        switch state {
        case .authorized:
            // User is still authorized
            break
        case .revoked:
            // User revoked - sign them out
            signOut()
        case .notFound:
            // User not found - credential invalid
            signOut()
        case .transferred:
            // User transferred to a different Apple ID
            handleTransfer()
        @unknown default:
            break
        }
    }
}

Can I remove other social logins and just use email/password?

Yes. If your app only uses email/password authentication (your own system), SIWA is not required. However, removing social login options may reduce sign-up conversion rates.

The user used "Hide My Email" - how do I contact them?

Email the private relay address. Apple forwards it to their real email. You must configure your sending domain in Apple Developer Portal under Services → Sign in with Apple for Email Communication.

User signed up with SIWA but wants to switch to email/password?

You can implement account linking. Ask for their email (or use the one from SIWA if available), let them set a password, and store both auth methods for the same account. They can then use either to sign in.

I missed capturing the email on first sign-in. Can I get it again?

No. Apple only sends email/name once. The user would need to go to Settings → Apple ID → Password & Security → Apps Using Your Apple ID, remove your app, then sign in again. You can't programmatically trigger this.

Does Sign in with Apple work on web/Android?

Yes. Apple provides Sign in with Apple JS for web and REST APIs for any platform. If your iOS app uses SIWA, users should be able to access their account on other platforms too.