So, what is UI Compatibility Mode? It’s Apple’s way of ensuring that your app’s UI appears in macOS 26 and iOS 26 just as it did on previous OS versions. No Liquid Glass effects, no unexpected changes in control sizes or behavior, everything stays as you designed it. This means your pixel-perfect layouts from older OS versions, like Sequoia or iOS 18, will continue to look exactly as intended.

More technically, when UI Compatibility Mode is enabled, your app behaves as if it were compiled with an earlier SDK.

The caveat: Apple only guarantees this behavior while macOS 26 and iOS 26 are current. With the next major OS releases, this mode may no longer be available, so it’s a temporary solution.

The upside: At the time of writing, Apple is still refining these OS versions with point releases. If you need your app to run on macOS 26 or iOS 26 with full compatibility, you can enable UI Compatibility Mode in the Inspector Panel under Build Settings > macOS and Build Settings > iOS.

When enabled, both your debugged apps and the built versions (including those submitted to Apple via Publish) will look and behave on macOS 26 and iOS 26 as if they were compiled with the previous SDK. In fact, the behavior is even more consistent than if they had been compiled using the prior Xojo release.

Below, you can see how the same app appears when running on macOS 26 and iOS 26 with UI Compatibility Mode turned off (showing Liquid Glass and all the new UI effects), compared to how it looks when the switch is turned on:

The Last Word

All in all, macOS 26 and iOS 26 introduce a major UI overhaul, which can change the appearance of existing layouts. To help developers, Apple has added UI Compatibility Mode, which lets your apps appear on these new OS versions just as they did on previous releases—no Liquid Glass effects or layout changes. Technically, enabling this mode makes your app behave as if it were compiled with an earlier SDK. While Apple only guarantees this behavior for macOS 26 and iOS 26, it ensures consistency for both debugged and built apps, including those submitted via Publish.

UI Compatibility Mode gives you a choice: enable it to preserve your exact layouts across all OS versions, or leave it off to adopt the new macOS 26 and iOS 26 look and feel, which may require adjusting your UI for some quirks.

Javier Menendez is an engineer at Xojo and has been using Xojo since 1998. He lives in Castellón, Spain and hosts regular Xojo hangouts en español. Ask Javier questions on Twitter at @XojoES or on the Xojo Forum.

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macOS 26 and iOS 26

Over time, Apple has brought the user experiences of macOS and iOS closer together. macOS 26 and iOS 26, now aligned in version numbers, also share more similarities than ever in their user experience. These updates represent the most significant user experience changes from Apple since iOS was introduced in 2007 and Aqua for macOS seven years earlier. With such a big update, especially when designing elements to work on both large computers displays as well as small smartphone screens, it’s no surprise there’s some tweaking requiring after release. Clearly, Apple is still refining its platforms.

We continue to update Xojo as Apple defines its preferred user experience, ensuring that you can deliver the best possible experience to your users.

WinUI

We are also hard at work upgrading our Windows framework to WinUI, providing a modern user experience for Windows apps. You can see our progress in each release by enabling the Use WinUI (Experimental) option on the Advanced tab in Windows build settings. The “Experimental” label is a reminder that the feature is still evolving, and it will be removed once WinUI is fully ready. Our goal has always been to keep Xojo on a steady path, prepared for whatever challenges lie ahead.

Conclusion

On behalf of the entire Xojo team, I can say that we love what we do and we appreciate your support in allowing us to do it. We are Xojo users ourselves (after all, we make Xojo with Xojo) and we enjoy seeing what you make with it. With that in mind, feel free to tell us about your creations. Send your screenshots, descriptions and your story to hello@xojo.com.

There are two possible solutions:

• If your Mac still runs under macOS 15.7 Sequoia (or an earlier macOS version supported by Xojo’s Publish feature) with Xcode 26 installed, you can restore Publish feature compatibility by installing Xcode 16.4.x and making that version the active one in your toolchain (especially if you have multiple Xcode versions installed).
• If your Mac is running macOS 26.x Tahoe with Xcode 26 installed, Xojo’s Publish feature for macOS apps won’t work as expected, specifically when it attempts to retrieve the AppID from the App Store Connect. The good news is that by the time this error occurs, your app has already been successfully compiled and the .pkg file created. You can use Apple’s Transporter app to complete the final step of uploading the .pkg file to App Store Connect.

This issue has been fixed and the solution will be included in Xojo 2025r3. The update also improves how the App ID is retrieved by relying on the available provider listing. This rare issue could affect users whose Apple ID is associated with multiple publishing services, for example, if the same Apple ID is used for both app development and podcast publishing.

Once Xojo 2025r3 is released, the Publish feature will work as before on macOS Sequoia (and previous supported macOS versions), and it will also function properly with the new Xcode 26 toolchain – whether installed on Sequoia or on the latest macOS 26. Read more about Xojo Support for macOS 26 and iOS 26 on the Xojo Blog.

Javier Menendez is an engineer at Xojo and has been using Xojo since 1998. He lives in Castellón, Spain and hosts regular Xojo hangouts en español. Ask Javier questions on Twitter at @XojoES or on the Xojo Forum.

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