# start() Starts a web authentication session. ``` func start() -> Bool ``` ## Return Value A Boolean value indicating whether the web authentication session started successfully. ## Discussion Only call this method once for a given [`ASWebAuthenticationSession`](/documentation/AuthenticationServices/ASWebAuthenticationSession) instance after initialization. Calling the [`start()`](/documentation/AuthenticationServices/ASWebAuthenticationSession/start()) method on a canceled session results in a failure. In macOS, and for iOS apps with a deployment target of iOS 13 or later, after you call [`start()`](/documentation/AuthenticationServices/ASWebAuthenticationSession/start()), the session instance stores a strong reference to itself. To avoid deallocation during the authentication process, the session keeps the reference until after it calls the completion handler. For iOS apps with a deployment target earlier than iOS 13, your app must keep a strong reference to the session to prevent the system from deallocating the session while waiting for authentication to complete. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)