Universal apps

-A single macOS Universal app includes native binaries for Intel-based Macs and Apple Silicon Macs
-“Any Mac” destination in the toolbar builds a Universal app, even on Intel-based Macs
-Standard Architectures build setting defaults to Universal, and Xcode offers to upgrade your project if needed
-Run and debug the Intel binary within a Universal app by selecting “My Mac (Rosetta)” on a -Developer Transition Kit (DTK) from the Universal App Quick Start Program
NOTE: Xcode 12.2 adds support for macOS Big Sur and Universal apps.

Refined user interface for macOS Big Sur

-Document tabs open any type of document, including logs, asset catalogs, and UI files, in a lightweight editor tab
-Toolbar, icons, and sidebar designs match the beautiful new aesthetic of macOS Big Sur
-Navigator fonts track the size of the system setting or can be manually set to a custom size
-Organizer is completely redesigned and reports new app metrics, such as hitches in animation and scrolling

Swift and SwiftUI

-App lifecycle in SwiftUI enables entire apps to be written completely in SwiftUI for iOS, iPadOS, and macOS
-WidgetKit built on SwiftUI makes it easy to share code for widgets that run on iOS, iPadOS, and macOS
-SwiftUI performance is improved throughout, and new Lazy views efficiently handle enormous data sets
-Multiplatform templates make it easy to share SwiftUI code across all Apple platforms, customized for each
-SwiftUI Views can be turned into reusable components that appear in the Xcode library and in code completions
-Swift Package Manager supports resources and localizations, making it great for sharing SwiftUI components
-Improved Swift language diagnostics make it much easier to understand coding mistakes, especially in SwiftUI code

Mac Catalyst

-Mac idiom displays your app’s user interface in 100% native Mac size and scale for total customization
-Additional frameworks and controls are available, including HomeKit and AVCapture
-Keyboard APIs and OS integration make it easier to completely control your app with the keyboard
-Apps built with Mac Catalyst automatically inherit the new look and feel of macOS Big Sur