How do I open phone settings when a button is clicked?

SWIFT 5

if let settingsUrl = URL(string: UIApplication.openSettingsURLString) {

   UIApplication.shared.open(settingsUrl)

 }

In iOS 8+ you can do the following:

 func buttonClicked(sender:UIButton)
    {
        UIApplication.sharedApplication().openURL(NSURL(string: UIApplicationOpenSettingsURLString))
    }

Swift 4

    let settingsUrl = URL(string: UIApplicationOpenSettingsURLString)!
    UIApplication.shared.open(settingsUrl)

Using UIApplication.openSettingsURLString

Update for Swift 5.1

 override func viewDidAppear(_ animated: Bool) {
    let alertController = UIAlertController (title: "Title", message: "Go to Settings?", preferredStyle: .alert)

    let settingsAction = UIAlertAction(title: "Settings", style: .default) { (_) -> Void in

        guard let settingsUrl = URL(string: UIApplication.openSettingsURLString) else {
            return
        }

        if UIApplication.shared.canOpenURL(settingsUrl) {
            UIApplication.shared.open(settingsUrl, completionHandler: { (success) in
                print("Settings opened: \(success)") // Prints true
            })
        }
    }
    alertController.addAction(settingsAction)
    let cancelAction = UIAlertAction(title: "Cancel", style: .default, handler: nil)
    alertController.addAction(cancelAction)

    present(alertController, animated: true, completion: nil)
}

Swift 4.2

override func viewDidAppear(_ animated: Bool) {
    let alertController = UIAlertController (title: "Title", message: "Go to Settings?", preferredStyle: .alert)

    let settingsAction = UIAlertAction(title: "Settings", style: .default) { (_) -> Void in

        guard let settingsUrl = URL(string: UIApplicationOpenSettingsURLString) else {
            return
        }

        if UIApplication.shared.canOpenURL(settingsUrl) {
            UIApplication.shared.open(settingsUrl, completionHandler: { (success) in
                print("Settings opened: \(success)") // Prints true
            })
        }
    }
    alertController.addAction(settingsAction)
    let cancelAction = UIAlertAction(title: "Cancel", style: .default, handler: nil)
    alertController.addAction(cancelAction)

    present(alertController, animated: true, completion: nil)
}

⚠️ Be careful!

This answer is based on undocumented APIs and recently (since iOS12) Apple is rejecting apps with this approach.

Original answer below

Swift 5

UIApplication.shared.open(URL(string: UIApplication.openSettingsURLString)!, options: [:], completionHandler: nil)

Swift 4

UIApplication.shared.open(URL(string: UIApplicationOpenSettingsURLString)!, options: [:], completionHandler: nil)

NOTE: The following method works for all the versions below iOS 11, for higher versions the app might get rejected since it's a private API

Sometimes we want to take a user to settings other than our app settings. The following method will help you achieve that:

First, configure the URL Schemes in your project. You will find it in Target -> Info -> URL Scheme. click on + button and type prefs in URL Schemes

Swift 5

UIApplication.shared.open(URL(string: "App-prefs:Bluetooth")!)

Swift 3

UIApplication.shared.open(URL(string:"App-Prefs:root=General")!, options: [:], completionHandler: nil)

Swift

UIApplication.sharedApplication().openURL(NSURL(string:"prefs:root=General")!)

Objective-C

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"prefs:root=General"]];

and following are all the available URLs

**On IOS < 12 **

• prefs:root=General&path=About
• prefs:root=General&path=ACCESSIBILITY
• prefs:root=AIRPLANE_MODE
• prefs:root=General&path=AUTOLOCK
• prefs:root=General&path=USAGE/CELLULAR_USAGE
• prefs:root=Brightness
• prefs:root=Bluetooth
• prefs:root=General&path=DATE_AND_TIME
• prefs:root=FACETIME
• prefs:root=General
• prefs:root=General&path=Keyboard
• prefs:root=CASTLE
• prefs:root=CASTLE&path=STORAGE_AND_BACKUP
• prefs:root=General&path=INTERNATIONAL
• prefs:root=LOCATION_SERVICES
• prefs:root=ACCOUNT_SETTINGS
• prefs:root=MUSIC
• prefs:root=MUSIC&path=EQ
• prefs:root=MUSIC&path=VolumeLimit
• prefs:root=General&path=Network
• prefs:root=NIKE_PLUS_IPOD
• prefs:root=NOTES
• prefs:root=NOTIFICATIONS_ID
• prefs:root=Phone
• prefs:root=Photos
• prefs:root=General&path=ManagedConfigurationList
• prefs:root=General&path=Reset
• prefs:root=Sounds&path=Ringtone
• prefs:root=Safari
• prefs:root=General&path=Assistant
• prefs:root=Sounds
• prefs:root=General&path=SOFTWARE_UPDATE_LINK
• prefs:root=STORE
• prefs:root=TWITTER
• prefs:root=FACEBOOK
• prefs:root=General&path=USAGE prefs:root=VIDEO
• prefs:root=General&path=Network/VPN
• prefs:root=Wallpaper
• prefs:root=WIFI
• prefs:root=INTERNET_TETHERING
• prefs:root=Phone&path=Blocked
• prefs:root=DO_NOT_DISTURB

On IOS 13

• App-prefs:General&path=About
• App-prefs:AIRPLANE_MODE
• App-prefs:General&path=AUTOLOCK
• App-prefs:Bluetooth
• App-prefs:General&path=DATE_AND_TIME
• App-prefs:FACETIME
• App-prefs:General
• App-prefs:General&path=Keyboard
• App-prefs:CASTLE
• App-prefs:CASTLE&path=STORAGE_AND_BACKUP
• App-prefs:General&path=INTERNATIONAL
• App-prefs:MUSIC
• App-prefs:NOTES
• App-prefs:NOTIFICATIONS_ID
• App-prefs:Phone
• App-prefs:Photos
• App-prefs:General&path=ManagedConfigurationList
• App-prefs:General&path=Reset
• App-prefs:Sounds&path=Ringtone
• App-prefs:Sounds
• App-prefs:General&path=SOFTWARE_UPDATE_LINK
• App-prefs:STORE
• App-prefs:Wallpaper
• App-prefs:WIFI
• App-prefs:INTERNET_TETHERING

• App-prefs:DO_NOT_DISTURB

  Not tested

• App-prefs:TWITTER (??)

• App-prefs:FACEBOOK (??)
• App-prefs:NIKE_PLUS_IPOD (??)

Note: Network setting will not be opened in a simulator, but the link will work on a real device.