# onBackgroundURLSessionEvents(matching:_:) Adds an action to perform when events related to a URL session identified by a closure are waiting to be processed. ``` @MainActor @preconcurrency func onBackgroundURLSessionEvents(matching matchingBlock: ((String) -> Bool)? = nil, _ urlSessionEvent: @escaping (String, @escaping () -> Void) -> Void) -> some WidgetConfiguration ``` ## Parameters `urlSessionEvent` A closure that takes a string parameter called `identifier` and a closure called `completion`. ## Return Value A widget that triggers `urlSessionEvent` when events are generated for a `URLSession` with the specified identifier. ## Discussion When a widget initiates a background network request, the system delivers events related to the request directly to the widget extension instead of the containing app. To process the events, do the following: 1. Use the `identifier` parameter to determine if a corresponding `URLSession` object exists. If the system hasn’t terminated your widget extension, maintain a reference to the same `URLSession` object you used for the original background network request. If the system terminated your widget extension, use the identifier to create a new `URLSession` object so it can receive the events. You might consider lazily initializing, and caching, the `URLSession` objects in a central location so that your code works regardless of whether your extension remains active, is suspended, or is terminated. 2. Store a reference to the `completion` closure to invoke it after the system delivers all events. 3. After the system calls the `URLSession` delegate’s method, invoke the `completion` closure. --- 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)