# register(forTaskWithIdentifier:using:launchHandler:) Register a launch handler for the task with the associated identifier that’s executed on the specified queue. ``` func register(forTaskWithIdentifier identifier: String, using queue: dispatch_queue_t?, launchHandler: @escaping (BGTask) -> Void) -> Bool ``` ## Parameters `identifier` A string containing the identifier of the task. `queue` A queue for executing the task. Pass `nil` to use a default background queue. `launchHandler` The system runs the block of code for the launch handler when it launches the app in the background. The block takes a single parameter, a [`BGTask`](/documentation/BackgroundTasks/BGTask) object used for assigning an expiration handler and for setting a completion status. The block has no return value. ## Return value Returns if the launch handler was registered. Returns if the identifier isn’t included in the `Info.plist`. ## Discussion Every identifier in the requires a handler. Registration of all launch handlers must be complete before the end of . > Important: Register each task identifier only once. The system kills the app on the second registration of the same task identifier. --- 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)