Liquid Glass and iOS 27

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Context

iOS 27 beta 1 and Xcode 27 beta 1 are available since WWDC 2027.
Thus, the promises about Liquid Glass and its deactivation should be checked.

TL ; DR

For Xcode 26.4

If the UIDesignRequiresCompatibility flag is defined (i.e. set to YES) in Xcode 26:

• no effect on iOS 18 and lower because Liquid Glass unavailable, legacy custom tab bar displayed
• on iOS 26, legacy custom tab bar displayed because flag is considered
• cannot compile for Xcode 27, but same logic as iOS 26

If the UIDesignRequiresCompatibility flag is missing or NO in Xcode 26:

• no effect on iOS 18 and lower because Liquid Glass unavailable, legacy custom tab bar displayed
• on iOS 26, glassified tab bar displayed
• cannot compile for Xcode 27, but same logic as iOS 26

For Xcode 27 (beta 1)

If the UIDesignRequiresCompatibility flag is defined (i.e. set to YES) in Xcode 27:

• no effect on iOS 18 and lower because Liquid Glass unavailable, legacy custom tab bar displayed
• on iOS 26, legacy custom tab bar displayed because flag is considered
• on iOS 27, flag is ignored, glassified tab bar is displayed with custom elements added for legacy layout

If the UIDesignRequiresCompatibility flag is missing or NO in Xcode 27:

• no effect on iOS 18 and lower because Liquid Glass unavailable, legacy custom tab bar displayed
• on iOS 26, glassified tab bar displayed
• on iOS 27, glassified tab bar displayed

Conclusion

Tip

Stop using the UIDesignRequiresCompatibility flag, overall if you use Xcode 27

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UIDesignRequiresCompatibility flag

Adding this flag in a new Xcode 27 beta 1 project can crash Xcode.

The documentation about this flag says:

The system ignores this key when you build for iOS 27 or later, iPadOS 27 or later, Mac Catalyst 27 or later, macOS 27 or later, or tvOS 27 or later.

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Transparency settings

iOS 27 can let user define the amount of transparency to apply

In Liquid Glass settings

video.-20260609-080921-72bd90e3.mp4

Design System Toolbox (2.1.0, Xcode 26)

With highest transparency and Orange Theme

video.-20260609-081130-3599e6fa.mp4

Design Toolbox 2.1.0 (Xcode 26) on iOS 21 beta 1 with highest transparency.zip

With highest transparency and Sosh Theme

video.-20260609-083308-b5e4f852.mp4

With lowest transparency

video.-20260609-081609-77f19f0b.mp4

Design Toolbox 2.1.0 (Xcode 26) on iOS 21 beta 1 witho lowest transparency.zip

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Side by side comparisons

With disabling flag

Here is the design system toolbox (develop version, 2.2.0-beta.2) build with Xcode 27 on simulators using iOS 19, iOS 26 and iOS 27 and without UIDesignRequiresCompatibility set to YES

Enregistrement.de.l.ecran.2026-06-09.a.12.40.38.mov

Note

For iOS 18, no issue, Liquid Glass unavailable.
For iOS 26, Liquid Glass is not applied because disabled, same style for the tab bar as for iOS 18.
For iOS 27, Liquid Glass is applied, even if flag set to YES, and the decorative items like selected tab indicator and divider are still displayed.

Caution

For iOS 27 and Xcode 27 (both beta 1), result is not acceptable if flag is set to YES.

Without disabling flag / flag set to NO

Here is the design system toolbox (develop version, 2.2.0-beta.2) build with Xcode 27 on simulators using iOS 19, iOS 26 and iOS 27 and with UIDesignRequiresCompatibility set to NO

Enregistrement.de.l.ecran.2026-06-09.a.13.07.02.mov

Note

For iOS 18, no issue, Liquid Glass unavailable.
For iOS 26, Liquid Glass is applied
For iOS 27, Liquid Glass is applied, no remaining overlay items