# bytes(from:delegate:) Retrieves the contents of a given URL and delivers an asynchronous sequence of bytes. ``` func bytes(from url: URL, delegate: (any URLSessionTaskDelegate)? = nil) async throws -> (URLSession.AsyncBytes, URLResponse) ``` ## Parameters `url` The URL to retrieve. `delegate` A delegate that receives life cycle and authentication challenge callbacks as the transfer progresses. ## Return Value An asynchronously-delivered tuple that contains a [`URLSession.AsyncBytes`](/documentation/Foundation/URLSession/AsyncBytes) sequence to iterate over, and a [`URLResponse`](/documentation/Foundation/URLResponse). ## Discussion Use this method when you want to process the bytes while the transfer is underway. You can use a `for`-`await`-`in` loop to handle each byte. For textual data, use the [`URLSession.AsyncBytes`](/documentation/Foundation/URLSession/AsyncBytes) properties , , or to receive the content as asynchronous sequences of those types. To wait until the session finishes transferring data and receive it in a single [`Data`](/documentation/Foundation/Data) instance, use [`data(from:delegate:)`](/documentation/Foundation/URLSession/data(from:delegate:)). --- 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)