---
title: "cancel(byProducingResumeData:)"
framework: foundation
role: symbol
role_heading: Instance Method
path: "foundation/urlsessiondownloadtask/cancel(byproducingresumedata:)"
---

# cancel(byProducingResumeData:)

Cancels a download and calls a callback with resume data for later use.

## Declaration

```swift
func cancel(byProducingResumeData completionHandler: @escaping @Sendable (Data?) -> Void)
```

```swift
func cancelByProducingResumeData() async -> Data?
```

## Parameters

- `completionHandler`: A completion handler that is called when the download has been successfully canceled. If the download is resumable, the completion handler is provided with a resumeData object. Your app can later pass this object to a session’s doc://com.apple.foundation/documentation/Foundation/URLSession/downloadTask(withResumeData:) or doc://com.apple.foundation/documentation/Foundation/URLSession/downloadTask(withResumeData:completionHandler:) method to create a new task that resumes the download where it left off. This block is not guaranteed to execute in a particular thread context. As such, you may want specify an appropriate dispatch queue in which to perform any work.

## Mentioned in

Pausing and resuming downloads Pausing and resuming uploads

## Discussion

Discussion A download can be resumed only if the following conditions are met: The resource has not changed since you first requested it The task is an HTTP or HTTPS GET request The server provides either the ETag or Last-Modified header (or both) in its response The server supports byte-range requests The temporary file hasn’t been deleted by the system in response to disk space pressure