General: DevForums tag: Background Tasks Background Tasks framework documentation UIApplication background tasks documentation ProcessInfo expiring activity documentation watchOS background execution documentation WWDC 2020 Session 10063 Background execution demystified — This is critical resource. Watch it! WWDC 2022 Session 10142 Efficiency awaits: Background tasks in SwiftUI iOS Background Execution Limits DevForums post UIApplication Background Task Notes DevForums post Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com"

Hello Apple Developer Team, I am facing an issue with remote notifications in my iOS app. When the app is in a terminated (kill) state, notifications are successfully received by the device, but none of the app's handlers (like _firebaseMessagingBackgroundHandler in Flutter) are invoked. This is impacting our ability to process silent notifications or perform background tasks reliably when the app is not running. Steps to reproduce: Send a remote notification with content-available: 1 in the payload. Confirm the notification is received by the device while the app is in kill mode. Observe that no background or foreground notification methods are triggered in the app. Expected Behavior: The app should invoke the background handler to process the notification payload, even in a terminated state. Observed Behavior: The notification is delivered to the device, but no app-level processing occurs because none of the methods are triggered. Can you please confirm if this is the intended behavior due to iOS limitations, or if there is a configuration or alternative solution to allow background handlers to execute in such scenarios? Any guidance or clarification would be highly appreciated. Thank you!

The application was initially written in Swift, and we released an update where the app was rewritten in Flutter. Currently, we are adding a widget natively written in SwiftUI to the Home screen. The widget updates are managed by BGTaskScheduler. In BGTaskScheduler, an API request is made to fetch the latest data. The data is then processed to calculate an average value, which is subsequently sent to UserDefaults. The widget displays data fetched from UserDefaults. The minimum update interval is set to 30 minutes. When testing the widget updates through a build in Xcode, the widget updates as expected at the specified interval. However, when this build was provided to users via TestFlight, the widget does not update for them. Could this issue be related to TestFlight’s resource limitations? Is there any guarantee that releasing this version will ensure the widget updates correctly for users?

Hello, I have a some problem with background fetch. In my app I use background modes for fetch data and display on my home widget iPhone. Its working correct when I built app on my phone from Xcode but when I distribute my app on TestFlight my home widget not updating at all. Help me understand if this issue is only due to TestFlight resources, or should I try releasing the app and hope that it will work in the release version?

We run simple iOS Swift code triggered by a remote notification: UserDefaults.standard.set("key", forKey: "value") It runs fine when the app is active or inactive, but when the device is closed/locked and the code is triggered, we see a warning in Xcode: Couldn't write values for keys ( key ) in CFPrefsPlistSource<0x3018802d0> (Domain: com.example, User: kCFPreferencesCurrentUser, ByHost: No, Container: (null), Contents Need Refresh: No): Path not accessible Not updating lastKnownShmemState in CFPrefsPlistSource<0x3018802d0> (Domain: com.example, User: kCFPreferencesCurrentUser, ByHost: No, Container: (null), Contents Need Refresh: No): 767 -> 767 The issue is that there seems to be no way to catch that warning. The value is set, when it's re-read the value is correct. But the value is never written to disk, so after an app restart/update the value is gone, potentially has an old wrong value. This code runs without any interruption, it's just showing the warning on iOS 17.7.1 on iPad: UserDefaults.standard.set("key", forKey: "value") UserDefaults.standard.synchronize() print("value: \(UserDefaults.standard.string(forKey: "key"))") Should there not be a way to catch this, so the code can act accordingly to the circumstances? It would be good to know inside the code that the value is not persisted. I would expect that an exception is generated somewhere which can be caught. It seems .completeFileProtectionUntilFirstUserAuthentication enables files to be written to disk while the device is closed/locked, can something similar be used for UserDefaults.standard?

Hello everyone! I'm having a problem with background tasks running in the foreground. When a user enters the app, a background task is triggered. I've written some code to check if the app is in the foreground and to prevent the task from running, but it doesn't always work. Sometimes the task runs in the background as expected, but other times it runs in the foreground, as I mentioned earlier. Could it be that I'm doing something wrong? Any suggestions would be appreciated. here is code: class BackgroundTaskService { @Environment(\.scenePhase) var scenePhase static let shared = BackgroundTaskService() private init() {} // MARK: - create task func createCheckTask() { let identifier = TaskIdentifier.check BGTaskScheduler.shared.getPendingTaskRequests { requests in if requests.contains(where: { $0.identifier == identifier.rawValue }) { return } self.createByInterval(identifier: identifier.rawValue, interval: identifier.interval) } } private func createByInterval(identifier: String, interval: TimeInterval) { let request = BGProcessingTaskRequest(identifier: identifier) request.earliestBeginDate = Date(timeIntervalSinceNow: interval) scheduleTask(request: request) } // MARK: submit task private func scheduleTask(request: BGProcessingTaskRequest) { do { try BGTaskScheduler.shared.submit(request) } catch { // some actions with error } } // MARK: background actions func checkTask(task: BGProcessingTask) { let today = Calendar.current.startOfDay(for: Date()) let lastExecutionDate = UserDefaults.standard.object(forKey: "lastCheckExecutionDate") as? Date ?? Date.distantPast let notRunnedToday = !Calendar.current.isDate(today, inSameDayAs: lastExecutionDate) guard notRunnedToday else { task.setTaskCompleted(success: true) createCheckTask() return } if scenePhase == .background { TaskActionStore.shared.getAction(for: task.identifier)?() } task.setTaskCompleted(success: true) UserDefaults.standard.set(today, forKey: "lastCheckExecutionDate") createCheckTask() } } And in AppDelegate: BGTaskScheduler.shared.register(forTaskWithIdentifier: "check", using: nil) { task in guard let task = task as? BGProcessingTask else { return } BackgroundTaskService.shared.checkNodeTask(task: task) } BackgroundTaskService.shared.createCheckTask()

Does anyone know how battery state notification (UIDevice.batteryStateDidChangeNotification) is supposed to work regarding app foreground/background state? Assume there is no other reason why the app is running in the background. I have enabled UIDevice.current.isBatteryMonitoringEnabled when the app was in the foreground. What should happen if the external power is later connected or removed when the app is in the background? The docs don't mention this. Possibilities include I don't get a notification, so I should check the state myself when the app next comes to the foreground. I'll get a notification when the app next comes to the foreground, if the state changed while it was in the background. The app will be woken up in the background to receive the notification. The app will be kept running in the background while isBatteryMonitoringEnabled is true. It looks as if it's doing either 3 or 4, which I find a bit surprising. But is this influenced by the fact that it's connected (wirelessly) to the debugger?

Within the output of command "sudo sfltool dumpbtm", in addition to records for UID 0/501/502/..., at the top of the output, there are also records for "UID -2" listed. ======================== Records for UID -2 : FFFFEEEE-DDDD-CCCC-BBBB-AAAAFFFFFFFE ======================== ServiceManagement migrated: true SharedFileList migrated: false LaunchServices registered: false Items: #1: UUID: FC60A3EA-E4B0-4D8C-BA07-1C6E2DF3AA52 Name: (null) Developer Name: (null) Type: developer (0x20) Flags: [ ] (0) Disposition: [disabled, allowed, visible, not notified] (0x2) Identifier: Unknown Developer URL: (null) Generation: 0 Embedded Item Identifiers: #1: 16.com.microsoft.teams.TeamsUpdaterDaemon But a uid with -2 should be invalid, and the guid "FFFFEEEE-DDDD-CCCC-BBBB-AAAAFFFFFFFE" followed looks also strange.

Can I integrate Timer along with liveUpdates(_:) in order to manipulate the frequency. Let say for example I need the user location ever 1 min. Is it possible to do so?

Hi, I would like to know if it is safe to call the uploadTask from URLSession from the main thread ? We've a user who is reporting repeated crashes at startup, here is the stack we see: Exception Type: EXC_CRASH (SIGKILL) Exception Codes: 0x0000000000000000, 0x0000000000000000 Termination Reason: FRONTBOARD 2343432205 <RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-update watchdog transgression: app<com.appspot.myApp(E7590BB1-722C-491D-9199-F867DE4B880A)>:2212 exhausted real (wall clock) time allowance of 10.00 seconds ProcessVisibility: Background ProcessState: Running WatchdogEvent: scene-update WatchdogVisibility: Background WatchdogCPUStatistics: ( "Elapsed total CPU time (seconds): 21.260 (user 10.230, system 11.030), 35% CPU", "Elapsed application CPU time (seconds): 0.006, 0% CPU" ) reportType:CrashLog maxTerminationResistance:Interactive> Triggered by Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 libsystem_kernel.dylib 0x1def7a688 mach_msg2_trap + 8 1 libsystem_kernel.dylib 0x1def7dd98 mach_msg2_internal + 80 2 libsystem_kernel.dylib 0x1def7dcb0 mach_msg_overwrite + 424 3 libsystem_kernel.dylib 0x1def7dafc mach_msg + 24 4 libdispatch.dylib 0x1968d8f14 _dispatch_mach_send_and_wait_for_reply + 544 5 libdispatch.dylib 0x1968d92b4 dispatch_mach_send_with_result_and_wait_for_reply + 60 6 libxpc.dylib 0x21714a930 xpc_connection_send_message_with_reply_sync + 256 7 Foundation 0x18d80a3ac __NSXPCCONNECTION_IS_WAITING_FOR_A_SYNCHRONOUS_REPLY__ + 16 8 Foundation 0x18d806b14 -[NSXPCConnection _sendInvocation:orArguments:count:methodSignature:selector:withProxy:] + 2160 9 CoreFoundation 0x18eb868dc ___forwarding___ + 1004 10 CoreFoundation 0x18eb86430 _CF_forwarding_prep_0 + 96 11 CFNetwork 0x1900c71e0 -[__NSURLBackgroundSession setupBackgroundSession] + 800 12 CFNetwork 0x1900b3e80 -[__NSURLBackgroundSession initWithConfiguration:delegate:delegateQueue:delegateDispatchQueue:] + 552 13 CFNetwork 0x1900b4784 +[NSURLSession _sessionWithConfiguration:delegate:delegateQueue:delegateDispatchQueue:] + 1496 14 MyApp 0x1054210b4 CombineBgXferRepository.session.getter (in MyApp) (CombineBgXferRepository.swift:62) + 7966900 15 MyApp 0x105422fa4 CombineBgXferRepository.startUploadTask(fileURL:request:) (in MyApp) (CombineBgXferRepository.swift:310) + 7974820 If it is ok to call this uploadTask from the main thread, does this crash indicate a problem with the operating system? Are there scenarios where the background upload service does not respond to requests?

Hello Apple Support, I’m facing an issue with Background Fetch in my React Native project. When I click on Simulate Background Fetch in Xcode, everything works as expected on the iOS Simulator—background tasks run smoothly, and data is fetched without issues. However, on a real device, the app goes to the background but doesn’t execute any of the scheduled background tasks, and it also remains in the background without terminating. Here’s some additional context: React Native Project: I’m using React Native to develop this app, and the background tasks involve: Getting User Location: Fetching the user’s location in the background. API Calls: Calling an API to fetch necessary information based on the user’s location. Scheduling Notifications and Alarms: Scheduling notifications and alarms based on the API response data. Simulator vs. Real Device: In the iOS Simulator, all these background tasks trigger and function correctly when I simulate Background Fetch. On the real device, however, none of these tasks are triggered when I try to simulate Background Fetch. The app only moves to the background without performing any tasks or getting terminated. Device and Configuration Details: iOS Version: 17 Device Model: Iphone xs, Iphone 11, iphone 7 Background Modes: Background Fetch is enabled in Capabilities, and I’ve set the fetch interval to the minimum for testing. I’ve verified that all configurations are correctly set, and I’ve tried restarting the device and Xcode, but the issue persists. Is there something specific about Background Fetch that could prevent it from functioning as expected on physical devices? Any guidance on troubleshooting or additional steps would be highly appreciated. Thank you!

Our application has seen a surge in the volume of background launches starting from April and May, and we want to know under what circumstances the application can be launched from the background. First, here's how I determined background launches: we analyze user logs and append UIApplication.appState to each line of log, finding that every log from the start to the end of user sessions has an appState of UIApplicationStateBackground. By checking the "ActivePrewarm" in main() and printing the launch options from application:didFinishLaunchingWithOptions:, we found several scenarios for background launches: launchOptions has a value with the key UIApplicationLaunchOptionsRemoteNotificationKey. launchOptions has no value and there is no "ActivePrewarm." launchOptions has no value but has "ActivePrewarm." I would like to know: Under what circumstances will notifications trigger a background launch (I cannot replicate this locally)? Under what circumstances does an application launch in the background and trigger application:didFinishLaunchingWithOptions: but without any launch options? I hope informations below can provide some insights. Regarding "ActivePrewarm," I've read various questions and answers in the Apple Developer Forums, such as this thread, which states that "ActivePrewarm" does not trigger application:didFinishLaunchingWithOptions: but occurs due to certain behaviors in the application. I would like to know what behaviors may cause this background launch, as there is no information in the launch options, or how I can identify what behaviors triggered it. Specifically, based on that same thread, I've tried to gather more information using runningboardd, and I've currently identified two special cases: When I restart my phone and unlock it after a short period, there is information: &lt;RBSDomainAttribute| domain:"com.apple.dasd" name:"DYLDLaunch" sourceEnvironment:"(null)"&gt; ]&gt; Every day, at intervals of a few hours, there is information: &lt;RBSDomainAttribute| domain:"com.apple.dasd" name:"DYLDLaunch" sourceEnvironment:"(null)"&gt; ]&gt; Then, the following similar information follows: 12:15:56.047625+0800 runningboardd Executing launch request for app&lt;{my_bundle_id}((null))&gt; (DAS Prewarm launch) 12:15:56.050311+0800 runningboardd Creating and launching job for: app&lt;{my_bundle_id}((null))&gt; 12:15:56.050333+0800 runningboardd _mutateContextIfNeeded called for {my_bundle_id} 12:15:56.080560+0800 runningboardd app&lt;{my_bundle_id}((null))&gt;: -[RBPersonaManager personaForIdentity:context:personaUID:personaUniqueString:] required 0.000954 ms (wallclock); resolved to {1000, 39E408CF-2E67-4DB0-BF73-CFC5792285CD} 12:15:56.080632+0800 runningboardd 'app&lt;{my_bundle_id}(39E408CF-2E67-4DB0-BF73-CFC5792285CD)&gt;' Skipping container path lookup because containerization was prevented (&lt;RBSLaunchContext: 0xcd8cc9180&gt;) 12:15:56.080939+0800 runningboardd 'app&lt;{my_bundle_id}(39E408CF-2E67-4DB0-BF73-CFC5792285CD)&gt;' Constructed job description: &lt;dictionary: 0xcd8aa2a00&gt; { count = 19, transaction: 0, voucher = 0x0, contents = *** } 12:15:56.084839+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] Memory Limits: active 4096 inactive 4096 &lt;private&gt; 12:15:56.084861+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] This process will be managed. 12:15:56.084882+0800 runningboardd Now tracking process: [app&lt;{my_bundle_id}((null))&gt;:1649] 12:15:56.084928+0800 runningboardd Calculated state for app&lt;{my_bundle_id}((null))&gt;: running-active (role: Background) (endowments: (null)) 12:15:56.086762+0800 runningboardd Using default underlying assertion for app: [app&lt;{my_bundle_id}((null))&gt;:1649] 12:15:56.086977+0800 runningboardd Acquiring assertion targeting [app&lt;{my_bundle_id}((null))&gt;:1649] from originator [app&lt;{my_bundle_id}((null))&gt;:1649] with description &lt;RBSAssertionDescriptor| "RB Underlying Assertion" ID:33-33-23101 target:1649 attributes:[ &lt;RBSDomainAttribute| domain:"com.apple.underlying" name:"defaultUnderlyingAppAssertion" sourceEnvironment:"(null)"&gt;, &lt;RBSAcquisitionCompletionAttribute| policy:AfterApplication&gt; ]&gt; 12:15:56.087203+0800 runningboardd Assertion 33-33-23101 (target:[app&lt;{my_bundle_id}((null))&gt;:1649]) will be created as active 12:15:56.087946+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] reported to RB as running 12:15:56.088053+0800 runningboardd Calculated state for app&lt;{my_bundle_id}((null))&gt;: running-active (role: Background) (endowments: (null)) 12:15:56.088114+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] Set jetsam priority to 0 [0] flag[1] 12:15:56.088136+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] Resuming task. 12:15:56.088211+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] Set darwin role to: Background 12:15:56.088449+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] set Memory Limits to Hard Inactive (4096) 12:15:56.089314+0800 runningboardd Successfully acquired underlying assertion for [app&lt;{my_bundle_id}((null))&gt;:1649] 12:15:56.589755+0800 runningboardd Invalidating assertion 33-76-23100 (target:app&lt;{my_bundle_id}((null))&gt;) from originator [osservice&lt;com.apple.dasd&gt;:76] 12:15:56.590332+0800 runningboardd Removed last relative-start-date-defining assertion for process app&lt;{my_bundle_id}((null))&gt; 12:15:56.593760+0800 runningboardd [app&lt;{my_bundle_id}((null))&gt;:1649] Suspending task. 12:15:56.594120+0800 runningboardd Calculated state for app&lt;{my_bundle_id}((null))&gt;: running-suspended (role: None) (endowments: (null)) From these logs, I understand that the system is accelerating the launch speed of the application. But the time interval between these two logs below is very short, which suggests that the prewarm is executed just before main, and then the process is suspended. Is this understanding correct? 12:15:56.089314+0800 runningboardd Successfully acquired underlying assertion ... 12:15:56.589755+0800 runningboardd Invalidating assertion ... Regarding "DAS DYLD3 Closure Generation," I speculate that after a user restarts their phone, the system uses DYLD3 to prepare closures for frequently used applications, allowing for faster application launches. Is this assumption correct?

Greetings, does anyone know if can I use background capabilities to refresh auth token safely without be aware of the OS kill this task? Is there any Apple Oficial recommended flow to handle that? thanks

Per Quinn the Eskimo's great summary post I am looking for the WWDC 2020 Session 10063 "Background execution demystified" but all links seem to be broken or redirecting elsewhere. Does anyone know where one could find a reputable copy of the video to watch as we explore background execution?

I am developing an application usinh native apps, where the app needs to continuously sync data (such as daily tasks and orders) even when offline or running in the background. However, on iOS, the background sync stops after 30 seconds, limiting the functionality. The Background Sync API and Service Workers seem restricted on iOS, causing syncing to fail when the app is in the background or offline. What is the best way to ensure continuous background synchronization on iOS? Additionally, what is the most efficient data storage approach for managing offline capabilities and syncing smoothly when the network is unstable and for the background sync?

My app is able to receive data updates when it is in foreground. however, when i move it in background then sync engine stops syncing until I again move app to foreground.

We are developing an application where it requires a feature to run the application in background get the latest updates as well but during the development process , we identified the background sync lasted only for 30 seconds. Kindly help in troubleshooting the issue

WatchOS app is running in the foreground and can wake up the iOS app, but it can't trigger didReceiveMessage in the iOS app. iOS and Watch apps in the foreground can communicate with each other without any issues. However, when my app is closed, even though it wakes up, it cannot communicate. Any ideas? Should I be using a background task ios app side?

I am using BGProcessingTaskRequest to fetch a API make my app up to date. Sometimes this background task execute with 10 minutes some times it take more than 10 mins, Some other times its never execute. But in my case im provide just 1 minute to BGProcessingTaskRequest.earliestBeginDate variable. And i will share my implementation here, My codes are, Called the register function before app launching. let taskId = "_________" func registerBackgroundTaks() { BGTaskScheduler.shared.register(forTaskWithIdentifier: taskId, using: nil) { task in self.handleBackgroundProcessRequest(task: task as! BGProcessingTask) } print("Receiver called") } Called the scheduleBackgroundPrecessingTask function when application enter in background mode. func scheduleBackgroundPrecessingTask() { let request = BGProcessingTaskRequest(identifier: taskId) request.requiresNetworkConnectivity = false // Need to true if your task need to network process. Defaults to false. request.requiresExternalPower = false request.earliestBeginDate = Date(timeIntervalSinceNow: 1 * 60) // Featch Image Count after 1 minute. do { try BGTaskScheduler.shared.submit(request) print("Process notification triggered") } catch { print("Could not schedule background process: \(error)") } } Could anyone share any concerns to my problem? or kindly clarify me why BGProcessingTaskRequest takes time randomly?

I'm trying to troubleshoot what is going on with my app. The app works just fine when the user is logged in. It's able to post data to my REST API just fine. But when the app goes in to the background, the BGAppRefreshTask fires off just fine, but it's unable to post its data. There payload is super small a two keys and two short strings and thats it. I've tried searching on kCFStreamErrorCodeKey -2103 and ErrorDomainKey 4 but not much comes up. Here is my error with the URL string altered... Error Domain=NSURLErrorDomain Code=-1001 "The request timed out." UserInfo={_kCFStreamErrorCodeKey=-2103, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <3126EFA1-00D3-4423-A31B-D40AB900292D>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=( "LocalDataTask <3126EFA1-00D3-4423-A31B-D40AB900292D>.<1>" ), NSLocalizedDescription=The request timed out., NSErrorFailingURLStringKey=https://my.example.com/myapi/v1/device, NSErrorFailingURLKey=https://my.example.com/myapi/v1/device, _kCFStreamErrorDomainKey=4}

I have an app that needs to refresh a server whenever a Contacts record is updated. I can observe Contacts, but that only seems to work when my app is running (and in foreground, which it cannot be on iPhone if the Contacts app is being updated). I want it to process, even if my app is in background, or has been terminated (swiped away), or after a phone restart. The only way I can think of is to periodically push a notification to the app from an external server. Is there any way to run a timer that sends a notification to the app on a periodic basis? The timers you can set seem to run even if the Clock app is swiped away, or following a phone restart. Is there anything like that I could use to wake my app periodically?