Liquid Glass on older iOS versions

What changed

Apple gave developers a temporary way out of the new design: the UIDesignRequiresCompatibility key in Info.plist. Its documentation calls it a key to use while you review your UI, and says the system ignores it when you build for iOS 27 or later.

So an app rebuilt with the iOS 27 SDK gets Liquid Glass on new systems. On older systems the effect does not exist. If you support both, your app looks split down the middle.

The native API

On systems that have it, UIKit draws glass with a UIGlassEffect inside a UIVisualEffectView. SwiftUI has the glassEffect modifier.

The same look on iOS 13 to 25

Theseus is a Swift package that draws the effect itself with Metal: blur, refraction, glare and spring animations. Add it with Swift Package Manager.

.package(url: "https://github.com/valzevul/Theseus.git", from: "1.0.0")

Then pick the native effect where it exists and Theseus where it does not.

let glass: UIView
if #available(iOS 26, *) {
    glass = UIVisualEffectView(effect: UIGlassEffect())
} else {
    let view = TheseusView()
    view.shape.cornerRadius = 20
    view.sourceView = backgroundView
    glass = view
}

Controls, too

Theseus includes a tab bar, a slider and a switch built on the same glass view. It mirrors the tint each view can take, and the clear to tinted setting iOS 27 gives users.

See Theseus

The key's behaviour follows Apple's documentation, read on 11 November 2026: UIDesignRequiresCompatibility.