# CFNetDiagnosticCreateWithURL(_:_:) Creates a CFNetDiagnosticRef from a CFURLRef. ``` func CFNetDiagnosticCreateWithURL(_ alloc: CFAllocator, _ url: CFURL) -> Unmanaged ``` ## Parameters `alloc` The allocator to use to allocate memory for the new object. Pass `NULL` or kCFAllocatorDefault to use the current default allocator. `url` CFURLRef that refers to the failed connection. ## Return Value CFNetDiagnosticRef that you can pass to [`CFNetDiagnosticDiagnoseProblemInteractively(_:)`](/documentation/CFNetwork/CFNetDiagnosticDiagnoseProblemInteractively(_:)) or [`CFNetDiagnosticCopyNetworkStatusPassively(_:_:)`](/documentation/CFNetwork/CFNetDiagnosticCopyNetworkStatusPassively(_:_:)). Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). ## Discussion This function uses a URL to create a reference to an instance of a CFNetDiagnostic object. You can pass the reference to [`CFNetDiagnosticDiagnoseProblemInteractively(_:)`](/documentation/CFNetwork/CFNetDiagnosticDiagnoseProblemInteractively(_:)) to open a Network Diagnostics window or to [`CFNetDiagnosticCopyNetworkStatusPassively(_:_:)`](/documentation/CFNetwork/CFNetDiagnosticCopyNetworkStatusPassively(_:_:)) to get a description of the connection referenced by `readStream` and `writeStream`. ### Special Considerations This function is thread safe as long as another thread does not alter the same CFNetDiagnosticRef at the same time. --- 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)