# URLSessionTaskDelegate A protocol that defines methods that URL session instances call on their delegates to handle task-level events. ``` protocol URLSessionTaskDelegate : URLSessionDelegate ``` ## Overview You use this protocol in one of two ways, depending on how you use a [`URLSession`](/documentation/Foundation/URLSession): - If you create tasks with Swift’s `async`-`await` syntax, using methods like [`bytes(for:delegate:)`](/documentation/Foundation/URLSession/bytes(for:delegate:)) and [`data(for:delegate:)`](/documentation/Foundation/URLSession/data(for:delegate:)), you pass a `delegate` argument of this type. The delegate receives callbacks for things like task progress, while the call point awaits the completion of the task. - If you add tasks to the session with methods like [`dataTask(with:)`](/documentation/Foundation/URLSession/dataTask(with:)-10dy7) and [`downloadTask(with:)`](/documentation/Foundation/URLSession/downloadTask(with:)-1onj), then you implement this protocol’s methods in a [`delegate`](/documentation/Foundation/URLSession/delegate) you set on the session. This session delegate may also implement other protocols as appropriate, like [`URLSessionDownloadDelegate`](/documentation/Foundation/URLSessionDownloadDelegate) and [`URLSessionDataDelegate`](/documentation/Foundation/URLSessionDataDelegate). You can also assign a delegate of this type directly to the task to intercept callbacks before the task delivers them to the session’s delegate. > Note: > Your ``doc://com.apple.foundation/documentation/Foundation/URLSession`` object doesn’t need to have a delegate. If you don’t assign a delegate, the session uses a system-provided delegate. In this case, you must provide a completion callback or use the Swift `async`-`await` methods to obtain the data. ## Topics ### Handling task life cycle changes [`urlSession(_:task:didCompleteWithError:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:didCompleteWithError:)) Tells the delegate that the task finished transferring data. ### Handling redirects [`urlSession(_:task:willPerformHTTPRedirection:newRequest:completionHandler:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:willPerformHTTPRedirection:newRequest:completionHandler:)) Tells the delegate that the remote server requested an HTTP redirect. ### Working with upload tasks [`urlSession(_:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:didSendBodyData:totalBytesSent:totalBytesExpectedToSend:)) Periodically informs the delegate of the progress of sending body content to the server. [`urlSession(_:task:needNewBodyStream:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:needNewBodyStream:)) Tells the delegate when a task requires a new request body stream to send to the remote server. ### Handling authentication challenges [`urlSession(_:task:didReceive:completionHandler:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:didReceive:completionHandler:)) Requests credentials from the delegate in response to an authentication request from the remote server. [`URLSession.AuthChallengeDisposition`](/documentation/Foundation/URLSession/AuthChallengeDisposition) Constants passed by session or task delegates to the provided continuation block in response to an authentication challenge. ### Handling delayed and waiting tasks [`urlSession(_:task:willBeginDelayedRequest:completionHandler:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:willBeginDelayedRequest:completionHandler:)) Tells the delegate that a delayed URL session task will now begin loading. [`URLSession.DelayedRequestDisposition`](/documentation/Foundation/URLSession/DelayedRequestDisposition) The action to take on a delayed URL session task. [`urlSession(_:taskIsWaitingForConnectivity:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:taskIsWaitingForConnectivity:)) Tells the delegate that the task is waiting until suitable connectivity is available before beginning the network load. ### Collecting task metrics [`urlSession(_:task:didFinishCollecting:)`](/documentation/Foundation/URLSessionTaskDelegate/urlSession(_:task:didFinishCollecting:)) Tells the delegate that the session finished collecting metrics for the task. [`URLSessionTaskMetrics`](/documentation/Foundation/URLSessionTaskMetrics) An object encapsulating the metrics for a session task. --- 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)