# open(completionHandler:) Opens a document asynchronously. ``` func open(completionHandler: (@Sendable (Bool) -> Void)? = nil) ``` ## Parameters `completionHandler` A block with code to execute after the open operation concludes. The block returns no value and has one parameter: - `success`: if the open operation succeeds, otherwise . The block is invoked on the main queue. ## Discussion Call this method to begin the sequence of method calls that opens and reads a document asynchronously. The method obtains the file-system location of the document from the [`fileURL`](/documentation/UIKit/UIDocument/fileURL) property. After the open operation concludes, the code in `completionHandler` is executed. You can override this method if you want custom document-opening behavior, but if you do it’s recommended that you call the superclass implementation first (`super`). If you don’t call `super`, you should use the class to implement coordinated reading. The default implementation calls [`performAsynchronousFileAccess(_:)`](/documentation/UIKit/UIDocument/performAsynchronousFileAccess(_:)) to schedule the document-reading work for execution on a background queue and then, from the dispatched block, performs file coordination. The queued task then calls [`read(from:)`](/documentation/UIKit/UIDocument/read(from:)). --- 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)