In macOS Big Sur, we […] enable running your existing iOS apps as-is on Apple Silicon-based Macs.
Here, "as-is" really means "as-is." We enable the user on the Mac to purchase or download, through the Mac App Store, the application you've already made available on the iOS App Store. It is the exact same binary.
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For your app to be available in the Mac App Store, it must be compatible with the Mac.
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Compatible iOS apps are automatically available in the Mac App Store, but you can manage the availability of your app in App Store Connect. You might choose not to make your iOS app available in the Mac App Store if you already have a Mac app or are planning on shipping one or if your app doesn't make sense on the Mac.