# SCNetworkReachability ## Overview > Important: > All `SCNetworkReachability` functions are deprecated, because network conditions change too frequently for preflight reachability tests to be accurate and useful. Instead of trying to perform a preflight check, just attempt your connection. The connection may not be available immediately, but you can use in your to automatically connect as soon as it’s possible to do so. If you’re using the framework, you can monitor the state of an ( in Objective-C), which lets you know when the connection is waiting for a change in connectivity before automatically proceeding. In limited cases, if you need to change a network request based on the network you’re using, use to observe the system networking state. The `SCNetworkReachability` programming interface allows an application to determine the status of a system’s current network configuration and the reachability of a target host. A remote host is considered reachable when a data packet, sent by an application into the network stack, can leave the local device. Reachability doesn’t guarantee that the data packet will actually be received by the host. The `SCNetworkReachability` programming interface supports a synchronous and an asynchronous model. In the synchronous model, you get the reachability status by calling the [`SCNetworkReachabilityGetFlags(_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityGetFlags(_:_:)) function. In the asynchronous model, you can schedule the `SCNetworkReachability` object on the run loop of a client object’s thread. The client implements a callback function to receive notifications when the reachability status of a given remote host changes. Note that these functions follow Core Foundation naming conventions. A function that has “Create” or “Copy” in its name returns a reference you must release with the function. For information about detecting and interpreting errors generated by calling these functions, see [System Configuration](/documentation/SystemConfiguration/system-configuration). ## Topics ### Creating a Reachability Reference [`SCNetworkReachabilityCreateWithAddress(_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityCreateWithAddress(_:_:)) Creates a reachability reference to the specified network address. [`SCNetworkReachabilityCreateWithAddressPair(_:_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityCreateWithAddressPair(_:_:_:)) Creates a reachability reference to the specified network address. [`SCNetworkReachabilityCreateWithName(_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityCreateWithName(_:_:)) Creates a reachability reference to the specified network host or node name. ### Determining Reachability Status [`SCNetworkReachabilityGetFlags(_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityGetFlags(_:_:)) Determines if the specified network target is reachable using the current network configuration. ### Preparing to Determine Reachability [`SCNetworkReachabilityGetTypeID()`](/documentation/SystemConfiguration/SCNetworkReachabilityGetTypeID()) Returns the type identifier of all `SCNetworkReachability` instances. [`SCNetworkReachabilitySetCallback(_:_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilitySetCallback(_:_:_:)) Assigns a client to the specified target, which receives callbacks when the reachability of the target changes. [`SCNetworkReachabilityScheduleWithRunLoop(_:_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityScheduleWithRunLoop(_:_:_:)) Schedules the specified network target with the specified run loop and mode. [`SCNetworkReachabilityUnscheduleFromRunLoop(_:_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilityUnscheduleFromRunLoop(_:_:_:)) Unschedules the specified target from the specified run loop and mode. [`SCNetworkReachabilitySetDispatchQueue(_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilitySetDispatchQueue(_:_:)) Schedules callbacks for the specified target on the specified dispatch queue. ### Callbacks [`SCNetworkReachabilityCallBack`](/documentation/SystemConfiguration/SCNetworkReachabilityCallBack) Type of callback function used when the reachability of a network address or name changes. ### Data Types [`SCNetworkReachability`](/documentation/SystemConfiguration/SCNetworkReachability) The handle to a network address or name. [`SCNetworkReachabilityContext`](/documentation/SystemConfiguration/SCNetworkReachabilityContext) Structure containing user-specified data and callbacks used with [`SCNetworkReachabilitySetCallback(_:_:_:)`](/documentation/SystemConfiguration/SCNetworkReachabilitySetCallback(_:_:_:)). ### Constants [`SCNetworkReachabilityFlags`](/documentation/SystemConfiguration/SCNetworkReachabilityFlags) Flags that indicate the reachability of a network node name or address, including whether a connection is required, and whether some user intervention might be required when establishing a connection. --- 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)