Choosing a Specific Interface Style for Your iOS App

Supporting both light and dark appearances is a good practice, but you might have good reasons to opt out of appearance changes wholly or partially in your app. Views containing user-created content should always reflect the user’s choices. Similarly, you might choose a specific appearance for print-related views so that they reflect what the user sees on the printed page.

The system assumes that apps linked against the iOS 13 or later SDK support both light and dark appearances. In iOS, you specify the specific appearance you want by assigning a specific interface style to your window, view, or view controller. You can also disable support for Dark Mode entirely using an Info.plist key.

For general information about how to support Dark Mode, see Supporting Dark Mode in Your Interface.

When your interface must always appear in a light or dark style, regardless of the system setting, set the overrideUserInterfaceStyle property of the appropriate window, view, or view controller to that style. Overriding the interface style affects other objects in your interface as follows:

• View controllers—The view controller’s views and child view controllers adopt the style.

• Views—The view and all of its subviews adopt the style.

• Windows—Everything in the window adopts the style, including the root view controller and all presentation controllers that display content in that window.

The following code example enables a light appearance for a view controller and all of its views.

    override func viewDidLoad() {
        super.viewDidLoad()

        // Always adopt a light interface style.    
        overrideUserInterfaceStyle = .light
    }

Parent view controllers control the appearance of their contained child view controllers. To override the interface style for a child view controller, use the setOverrideTraitCollection(_:forChild:) method to assign new traits to that view controller. For custom presentations, you can similarly override the interface style of the presented view controller by assigning new traits to the overrideTraitCollection property of your UIPresentationController object.

The system automatically opts in any app linked against the iOS 13.0 or later SDK to both light and dark appearances. If you need extra time to work on your app's Dark Mode support, you can temporarily opt out by including the UIUserInterfaceStyle key (with a value of Light) in your app’s Info.plist file. Setting this key to Light causes the system to ignore the user's preference and always apply a light appearance to your app.