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# URLSessionDownloadDelegate

A protocol that defines methods that URL session instances call on their delegates to handle task-level events specific to download tasks.

```
protocol URLSessionDownloadDelegate : URLSessionTaskDelegate
```

## Overview

In addition to the methods in this protocol, be sure to implement the methods in the [`URLSessionTaskDelegate`](/documentation/Foundation/URLSessionTaskDelegate) and [`URLSessionDelegate`](/documentation/Foundation/URLSessionDelegate) protocols to handle events common to all task types and session-level events, respectively.

> Note:
> An ``doc://com.apple.foundation/documentation/Foundation/URLSession`` object need not have a delegate. If no delegate is assigned, a system-provided delegate is used, and you must provide a completion callback to obtain the data.

## Topics

### Handling download life cycle changes

[`urlSession(_:downloadTask:didFinishDownloadingTo:)`](/documentation/Foundation/URLSessionDownloadDelegate/urlSession(_:downloadTask:didFinishDownloadingTo:))

Tells the delegate that a download task has finished downloading.

### Resuming paused downloads

[`urlSession(_:downloadTask:didResumeAtOffset:expectedTotalBytes:)`](/documentation/Foundation/URLSessionDownloadDelegate/urlSession(_:downloadTask:didResumeAtOffset:expectedTotalBytes:))

Tells the delegate that the download task has resumed downloading.

### Receiving progress updates

[`urlSession(_:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:)`](/documentation/Foundation/URLSessionDownloadDelegate/urlSession(_:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:))

Periodically informs the delegate about the download’s progress.


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