Instance Property


A Boolean value that indicates whether connections may use the network when the user has specified Low Data Mode.


var allowsConstrainedNetworkAccess: Bool { get set }


In iOS 13 and later, users can set their device to use Low Data Mode as one of the Cellular Data Options in the Settings app. Users can turn on Low Data Mode to reduce your app’s network data usage. This property controls a URL session’s behavior when the user turns on Low Data Mode. If there are no nonconstrained network interfaces available and the session’s allowsConstrainedNetworkAccess property is false, any task created from the session fails. In this case, the error provided when the task fails has a networkUnavailableReason property whose value is NSURLErrorNetworkUnavailableReason.constrained.

Limit your app’s of use of constrained network access to user-initiated tasks, and put off discretionary tasks until a nonconstrained interface becomes available. To do this, set allowsConstrainedNetworkAccess (and allowsExpensiveNetworkAccess) to false and waitsForConnectivity to true. This way, your URLSessionTask waits for a suitable interface to become available before sending or receiving data.

See Also

Supporting Limited Modes

var allowsExpensiveNetworkAccess: Bool

A Boolean value that indicates whether connections may use a network interface that the system considers expensive.