iOS 27 Beta 4: Native Liquid Glass UITabBar renders with opaque milky/frosted background while identical code renders correctly on iOS 26.5
Environment
- Xcode 27 Beta 4
- iOS 27 Beta 4
- UIKit
- UITabBarController
- Storyboard based application
- Native UITabBar (no custom tab bar implementation)
- Device: iPhone 17 Pro Simulator (also reproducible on other iPhone simulators)
Problem
After upgrading to iOS 27 Beta 4, the native Liquid Glass tab bar appears significantly more opaque (milky/frosted gray) than on iOS 26.5.
The exact same application binary and configuration render correctly on iOS 26.5.
No custom blur or visual effect is being applied.
Current Configuration
let appearance = UITabBarAppearance()
appearance.configureWithDefaultBackground()
appearance.backgroundColor = nil
appearance.backgroundEffect = nil
appearance.shadowColor = .clear
tabBar.standardAppearance = appearance
tabBar.scrollEdgeAppearance = appearance
tabBar.isTranslucent = true
tabBar.backgroundColor = nil
tabBar.barTintColor = nil
tabBar.backgroundImage = nil
tabBar.shadowImage = nil
Runtime Verification
Verified at runtime:
tabBar.backgroundColor == nil
tabBar.barTintColor == nil
tabBar.isTranslucent == true
standardAppearance.backgroundColor == nil
standardAppearance.backgroundEffect == nil
scrollEdgeAppearance.backgroundColor == nil
scrollEdgeAppearance.backgroundEffect == nil
View Hierarchy
The runtime hierarchy contains Apple's native Liquid Glass implementation:
UITabBar
_UIBarItemPlatterView
_UILiquidLensView
BackdropView
ClearGlassView
_UIPortalView
_UITabSelectionView
Therefore UIKit is using the Liquid Glass implementation rather than falling back to a legacy blur.
Investigation Performed
The following were tested without changing behavior:
- Removed all custom blur views
- Removed custom overlays
- Removed refresh/recomposition code
- Removed layout invalidation
- Removed transform hacks
- Removed PageMenu
- Replaced entire first tab with a plain UITableViewController
- Replaced DiscoverVC completely
- Replaced nested collection views
- Rebuilt a minimal demo project using identical UITabBarAppearance code
The minimal demo renders correctly.
The production application renders with a much more opaque gray background.
Question
Has anything changed in the Liquid Glass compositor or backdrop sampling behavior in iOS 27 Beta 4?
Is there any new API or recommended configuration required to achieve the same transparency level as iOS 26.5?
If this is expected behavior, is there any supported way to control the opacity of the system Liquid Glass material?
Screenshots
Attach:
- iOS 26.5 screenshot
- iOS 27 Beta 4 screenshot
