How to remove all navigationbar back button title

If you want back arrow so following code put into AppDelegate file into didFinishLaunchingWithOptions method.

For Objective-C

 [[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) forBarMetrics:UIBarMetricsDefault];

For Swift

let BarButtonItemAppearance = UIBarButtonItem.appearance()
BarButtonItemAppearance.setTitleTextAttributes([NSForegroundColorAttributeName: UIColor.clear], for: .normal)

Another option give below.

In Objective C

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];

In Swift

self.navigationItem.backBarButtonItem = UIBarButtonItem(title:"", style:.plain, target:nil, action:nil)

UPDATE :

    let BarButtonItemAppearance = UIBarButtonItem.appearance()

    let attributes: [NSAttributedStringKey: Any] = [
    BarButtonItemAppearance.setTitleTextAttributes([NSForegroundColorAttributeName: UIColor.clear], for: .normal)
            NSAttributedStringKey.font: UIFont.systemFont(ofSize: 0.1),
            NSAttributedStringKey.foregroundColor: UIColor.clear]

    BarButtonItemAppearance.setTitleTextAttributes(attributes, for: .normal)
    BarButtonItemAppearance.setTitleTextAttributes(attributes, for: .highlighted)

UPDATE SWIFT 4.1 :

    let attributes = [NSAttributedStringKey.font:  UIFont(name: "Helvetica-Bold", size: 0.1)!, NSAttributedStringKey.foregroundColor: UIColor.clear]

    BarButtonItemAppearance.setTitleTextAttributes(attributes, for: .normal)
    BarButtonItemAppearance.setTitleTextAttributes(attributes, for: .highlighted)

Using Offset

UIBarButtonItem.appearance().setBackButtonTitlePositionAdjustment(UIOffsetMake(-1000, 0), for:UIBarMetrics.default)

I'm using this line of code in AppDelegate file into didFinishLaunchingWithOptions method to remove the backbutton title.

Swift 2.x

let barAppearace = UIBarButtonItem.appearance()
barAppearace.setBackButtonTitlePositionAdjustment(UIOffsetMake(0, -60), forBarMetrics:UIBarMetrics.Default)

Swift 3.x

UIBarButtonItem.appearance().setBackButtonTitlePositionAdjustment(UIOffsetMake(0, -60), for:UIBarMetrics.default)

Swift 4.x

UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.clear], for: .normal)
    UIBarButtonItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.clear], for: UIControlState.highlighted)

Just need go to your Parent ViewController from where your other ViewControllers are dependent.

override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(true)
navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .Plain, target: nil, action: nil)}

Work's like charm on Swift 3

self.navigationController?.navigationBar.topItem?.title = " "