iPad Sidebar Backgrounds in iOS 26

WWDC 25: Build a UIKit app with the new design (see timestamp) shows how to use UIBackgroundExtensionView to extend iPad background images under the new Liquid Glass sidebars. The image is reflected and extended under the sidebar for a neat visual effect:

iOS 26 Sidebar Background Extension

You’ll notice how the mountain line seen under the translucent sidebar is a reflection of the visible mountain line.

Here’s some sample code:

class PrimaryViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .clear
        
        // Create your background content
        let posterImageView = UIImageView(image: .yosmite)
        posterImageView.contentMode = .scaleAspectFill
        
        // Wrap it in UIBackgroundExtensionView
        let extView = UIBackgroundExtensionView()
        extView.contentView = posterImageView
        
        // Add and constrain to fill the view
        view.addSubview(extView)
        extView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            extView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            extView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
            extView.topAnchor.constraint(equalTo: view.topAnchor),
            extView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        ])
    }
}

UIBackgroundExtensionView for iPad Sidebar Backgrounds