Background Processing Register, schedule, and execute background work on iOS using the BackgroundTasks framework, background URLSession, and background push notifications. Contents Info.plist Configuration BGTaskScheduler Registration BGAppRefreshTask Patterns BGProcessingTask Patterns BGContinuedProcessingTask (iOS 26+) Background URLSession Downloads Background Push Triggers Common Mistakes Review Checklist References Info.plist Configuration Every task identifier must be declared in Info.plist under BGTaskSchedulerPermittedIdentifiers , or submit(_:) throws BGTaskScheduler.Error.Code.notPermitted . < key
BGTaskSchedulerPermittedIdentifiers </ key
< array
< string
com.example.app.refresh </ string
< string
com.example.app.db-cleanup </ string
< string
com.example.app.export </ string
</ array
Also enable the required UIBackgroundModes : < key
UIBackgroundModes </ key
< array
< string
fetch </ string
< string
processing </ string
</ array
In Xcode: target > Signing & Capabilities > Background Modes > enable "Background fetch" and "Background processing". BGTaskScheduler Registration Register handlers before app launch completes. In UIKit, register in application(_:didFinishLaunchingWithOptions:) . In SwiftUI, register in the App initializer. UIKit Registration import BackgroundTasks @main class AppDelegate : UIResponder , UIApplicationDelegate { func application ( _ application : UIApplication , didFinishLaunchingWithOptions launchOptions : [ UIApplication . LaunchOptionsKey : Any ] ? ) -> Bool { BGTaskScheduler . shared . register ( forTaskWithIdentifier : "com.example.app.refresh" , using : nil // nil = main queue ) { task in self . handleAppRefresh ( task : task as ! BGAppRefreshTask ) } BGTaskScheduler . shared . register ( forTaskWithIdentifier : "com.example.app.db-cleanup" , using : nil ) { task in self . handleDatabaseCleanup ( task : task as ! BGProcessingTask ) } return true } } SwiftUI Registration import SwiftUI import BackgroundTasks @main struct MyApp : App { init ( ) { BGTaskScheduler . shared . register ( forTaskWithIdentifier : "com.example.app.refresh" , using : nil ) { task in BackgroundTaskManager . shared . handleAppRefresh ( task : task as ! BGAppRefreshTask ) } } var body : some Scene { WindowGroup { ContentView ( ) } } } BGAppRefreshTask Patterns Short-lived tasks (~30 seconds) for fetching small data updates. The system decides when to launch based on usage patterns. func scheduleAppRefresh ( ) { let request = BGAppRefreshTaskRequest ( identifier : "com.example.app.refresh" ) request . earliestBeginDate = Date ( timeIntervalSinceNow : 15 * 60 ) do { try BGTaskScheduler . shared . submit ( request ) } catch { print ( "Could not schedule app refresh: ( error ) " ) } } func handleAppRefresh ( task : BGAppRefreshTask ) { // Schedule the next refresh before doing work scheduleAppRefresh ( ) let fetchTask = Task { do { let data = try await APIClient . shared . fetchLatestFeed ( ) await FeedStore . shared . update ( with : data ) task . setTaskCompleted ( success : true ) } catch { task . setTaskCompleted ( success : false ) } } // CRITICAL: Handle expiration -- system can revoke time at any moment task . expirationHandler = { fetchTask . cancel ( ) task . setTaskCompleted ( success : false ) } } BGProcessingTask Patterns Long-running tasks (minutes) for maintenance, data processing, or cleanup. Runs only when device is idle and (optionally) charging. func scheduleProcessingTask ( ) { let request = BGProcessingTaskRequest ( identifier : "com.example.app.db-cleanup" ) request . requiresNetworkConnectivity = false request . requiresExternalPower = true request . earliestBeginDate = Date ( timeIntervalSinceNow : 60 * 60 ) do { try BGTaskScheduler . shared . submit ( request ) } catch { print ( "Could not schedule processing task: ( error ) " ) } } func handleDatabaseCleanup ( task : BGProcessingTask ) { scheduleProcessingTask ( ) let cleanupTask = Task { do { try await DatabaseManager . shared . purgeExpiredRecords ( ) try await DatabaseManager . shared . rebuildIndexes ( ) task . setTaskCompleted ( success : true ) } catch { task . setTaskCompleted ( success : false ) } } task . expirationHandler = { cleanupTask . cancel ( ) task . setTaskCompleted ( success : false ) } } BGContinuedProcessingTask (iOS 26+) A task initiated in the foreground by a user action that continues running in the background. The system displays progress via a Live Activity. Conforms to ProgressReporting . Availability: iOS 26.0+, iPadOS 26.0+ Unlike BGAppRefreshTask and BGProcessingTask , this task starts immediately from the foreground. The system can terminate it under resource pressure, prioritizing tasks that report minimal progress first. import BackgroundTasks func startExport ( ) { let request = BGContinuedProcessingTaskRequest ( identifier : "com.example.app.export" , title : "Exporting Photos" , subtitle : "Processing 247 items" ) // .queue: begin as soon as possible if can't run immediately // .fail: fail submission if can't run immediately request . strategy = . queue BGTaskScheduler . shared . register ( forTaskWithIdentifier : "com.example.app.export" , using : nil ) { task in let continuedTask = task as ! BGContinuedProcessingTask Task { await self . performExport ( task : continuedTask ) } } do { try BGTaskScheduler . shared . submit ( request ) } catch { print ( "Could not submit continued processing task: ( error ) " ) } } func performExport ( task : BGContinuedProcessingTask ) async { let items = await PhotoLibrary . shared . itemsToExport ( ) let progress = task . progress progress . totalUnitCount = Int64 ( items . count ) for ( index , item ) in items . enumerated ( ) { if Task . isCancelled { break } await PhotoExporter . shared . export ( item ) progress . completedUnitCount = Int64 ( index + 1 ) // Update the user-facing title/subtitle task . updateTitle ( "Exporting Photos" , subtitle : " ( index + 1 ) of ( items . count ) complete" ) } task . setTaskCompleted ( success : ! Task . isCancelled ) } Check whether the system supports the resources your task needs: let supported = BGTaskScheduler . shared . supportedResources if supported . contains ( . gpu ) { request . requiredResources = . gpu } Background URLSession Downloads Use URLSessionConfiguration.background for downloads that continue even after the app is suspended or terminated. The system handles the transfer out of process. class DownloadManager : NSObject , URLSessionDownloadDelegate { static let shared = DownloadManager ( ) private lazy var session : URLSession = { let config = URLSessionConfiguration . background ( withIdentifier : "com.example.app.background-download" ) config . isDiscretionary = true config . sessionSendsLaunchEvents = true return URLSession ( configuration : config , delegate : self , delegateQueue : nil ) } ( ) func startDownload ( from url : URL ) { let task = session . downloadTask ( with : url ) task . earliestBeginDate = Date ( timeIntervalSinceNow : 60 ) task . resume ( ) } func urlSession ( _ session : URLSession , downloadTask : URLSessionDownloadTask , didFinishDownloadingTo location : URL ) { // Move file from tmp before this method returns let dest = FileManager . default . urls ( for : . documentDirectory , in : . userDomainMask ) [ 0 ] . appendingPathComponent ( "download.dat" ) try ? FileManager . default . moveItem ( at : location , to : dest ) } func urlSession ( _ session : URLSession , task : URLSessionTask , didCompleteWithError error : ( any Error ) ? ) { if let error { print ( "Download failed: ( error ) " ) } } } Handle app relaunch — store and invoke the system completion handler: // In AppDelegate: func application ( _ application : UIApplication , handleEventsForBackgroundURLSession identifier : String , completionHandler : @escaping ( ) -> Void ) { backgroundSessionCompletionHandler = completionHandler } // In URLSessionDelegate — call stored handler when events finish: func urlSessionDidFinishEvents ( forBackgroundURLSession session : URLSession ) { Task { @MainActor in self . backgroundSessionCompletionHandler ? ( ) self . backgroundSessionCompletionHandler = nil } } Background Push Triggers Silent push notifications wake your app briefly to fetch new content. Set content-available: 1 in the push payload. { "aps" : { "content-available" : 1 } , "custom-data" : "new-messages" } Handle in AppDelegate: func application ( _ application : UIApplication , didReceiveRemoteNotification userInfo : [ AnyHashable : Any ] , fetchCompletionHandler completionHandler : @escaping ( UIBackgroundFetchResult ) -> Void ) { Task { do { let hasNew = try await MessageStore . shared . fetchNewMessages ( ) completionHandler ( hasNew ? . newData : . noData ) } catch { completionHandler ( . failed ) } } } Enable "Remote notifications" in Background Modes and register: UIApplication . shared . registerForRemoteNotifications ( ) Common Mistakes 1. Missing Info.plist identifiers // DON'T: Submit a task whose identifier isn't in BGTaskSchedulerPermittedIdentifiers let request = BGAppRefreshTaskRequest ( identifier : "com.example.app.refresh" ) try BGTaskScheduler . shared . submit ( request ) // Throws .notPermitted // DO: Add every identifier to Info.plist BGTaskSchedulerPermittedIdentifiers //
com.example.app.refresh 2. Not calling setTaskCompleted(success:) // DON'T: Return without marking completion -- system penalizes future scheduling func handleRefresh ( task : BGAppRefreshTask ) { Task { let data = try await fetchData ( ) await store . update ( data ) // Missing: task.setTaskCompleted(success:) } } // DO: Always call setTaskCompleted on every code path func handleRefresh ( task : BGAppRefreshTask ) { let work = Task { do { let data = try await fetchData ( ) await store . update ( data ) task . setTaskCompleted ( success : true ) } catch { task . setTaskCompleted ( success : false ) } } task . expirationHandler = { work . cancel ( ) task . setTaskCompleted ( success : false ) } } 3. Ignoring the expiration handler // DON'T: Assume your task will run to completion func handleCleanup ( task : BGProcessingTask ) { Task { await heavyWork ( ) } // No expirationHandler -- system terminates ungracefully } // DO: Set expirationHandler to cancel work and mark completed func handleCleanup ( task : BGProcessingTask ) { let work = Task { await heavyWork ( ) } task . expirationHandler = { work . cancel ( ) task . setTaskCompleted ( success : false ) } } 4. Scheduling too frequently // DON'T: Request refresh every minute -- system throttles aggressively request . earliestBeginDate = Date ( timeIntervalSinceNow : 60 ) // DO: Use reasonable intervals (15+ minutes for refresh) request . earliestBeginDate = Date ( timeIntervalSinceNow : 15 * 60 ) // earliestBeginDate is a hint -- the system chooses actual launch time 5. Over-relying on background time // DON'T: Start a 10-minute operation assuming it will finish func handleRefresh ( task : BGAppRefreshTask ) { Task { await tenMinuteSync ( ) } } // DO: Design work to be incremental and cancellable func handleRefresh ( task : BGAppRefreshTask ) { let work = Task { for batch in batches { try Task . checkCancellation ( ) await processBatch ( batch ) await saveBatchProgress ( batch ) } task . setTaskCompleted ( success : true ) } task . expirationHandler = { work . cancel ( ) task . setTaskCompleted ( success : false ) } } Review Checklist All task identifiers listed in BGTaskSchedulerPermittedIdentifiers Required UIBackgroundModes enabled ( fetch , processing ) Tasks registered before app launch completes setTaskCompleted(success:) called on every code path expirationHandler set and cancels in-flight work Next task scheduled inside the handler (re-schedule pattern) earliestBeginDate uses reasonable intervals (15+ min for refresh) Background URLSession uses delegate (not async/closures) Background URLSession file moved in didFinishDownloadingTo before return handleEventsForBackgroundURLSession stores and calls completion handler Background push payload includes content-available: 1 fetchCompletionHandler called promptly with correct result BGContinuedProcessingTask reports progress via ProgressReporting Work is incremental and cancellation-safe ( Task.checkCancellation() ) No blocking synchronous work in task handlers References See references/background-task-patterns.md for extended patterns, background URLSession edge cases, debugging with simulated launches, and background push best practices. BGTaskScheduler BGAppRefreshTask BGProcessingTask BGContinuedProcessingTask (iOS 26+) BGContinuedProcessingTaskRequest (iOS 26+) Using background tasks to update your app Performing long-running tasks on iOS and iPadOS