<!--
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  "availability" : [
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  "framework" : "AppKit",
  "identifier" : "/documentation/AppKit/NSWorkspace/duplicate(_:completionHandler:)",
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    "preciseIdentifier" : "c:objc(cs)NSWorkspace(im)duplicateURLs:completionHandler:"
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  "title" : "duplicate(_:completionHandler:)"
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# duplicate(_:completionHandler:)

Duplicates the specified URLS asynchronously in the same manner as the Finder.

```
func duplicate(_ URLs: [URL], completionHandler handler: (@Sendable ([URL : URL], (any Error)?) -> Void)? = nil)
```

## Parameters

`URLs`

An array of <doc://com.apple.documentation/documentation/Foundation/NSURL> objects representing the files to duplicate. This parameter must not be `nil`.

`handler`

The completion handler block object to call when the operation completes. You may specify `nil` for this parameter. If this parameter is not `nil`, you must call the [`duplicate(_:completionHandler:)`](/documentation/AppKit/NSWorkspace/duplicate(_:completionHandler:)) method from a block running on an active dispatch queue; your completion handler block is subsequently executed on the same dispatch queue.

    This block takes two parameters:

- newURLs: A dictionary parameter whose keys and values are <doc://com.apple.documentation/documentation/Foundation/NSURL> objects. Each key is a URL from the `URLs` parameter. The value of each key is a URL representing the location of the duplicated file. If this method could not duplicate a file, the corresponding URL is not included in the dictionary.
- error: If the operation succeeded for every file, this parameter is `nil`. If the operation failed for one or more files, the parameter contains an error object describing the overall result of the operation in a manner suitable for presentation to the user.

## Discussion

This method may cause a progress indicator, or other user interface element, to be shown by the Finder.

In macOS 10.6, this method requires the app to run its main run loop in a common mode. You can safely call this method from any thread of your app.

---

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