Migrating MacOS Apps to 64-bit Before the Apple Transition

David Ortinau

David

Apple has been moving towards 64-bit only applications on macOS for a number of releases. Last June, Apple started requiring Apps on the macOS App Store to be 64-bit only and macOS 10.13.4 and above prompt when launching 32-bit applications.

Apple Notification

Apple Transitions to 64-bit

This fall in macOS 10.15 (Catalina), Apple is completing their transition to 64-bit only by removing 32-bit support from macOS:

32-bit applications will not launch on macOS 10.15 (Catalina).

Though new Xamarin.Mac applications target 64-bit by default, any existing Xamarin.Mac applications that target 32-bit must be migrated to 64-bit to continue working in the future. Please see the documentation for instructions on how to migrate your application.

64-bit Support

Here are the various historical products and their support for 64-bit:

ProductAssembly Name64-bit support
MonoMacMonoMac.dllNo
Xamarin.Mac ClassicXamMac.dllNo
Xamarin.Mac UnifiedXamarin.Mac.dllYes
(if selected in Build Options “Supported Architectures”)

Following Apple’s Lead

Beginning with the release of Xcode 11 this fall, Xamarin.Mac will mirror Xcode and drop support for building 32-bit applications.

The Future of 32-bit Apps

In the rare event that you need the ability to build 32-bit applications long term, you must keep a development machine on 10.14.5 and Xcode 10.2 (or earlier) and not upgrade beyond the Visual Studio for Mac 8.2 release.

David Ortinau
David Ortinau

Senior Program Manager, Mobile Developer Tools

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