Apple released macOS Monterey (also known as macOS 12) in October of last year, complete with a revamped Safari web browser, improvements for Shortcuts and FaceTime, and much more. However, one of the most-anticipated features — Universal Control — was delayed to a future release. Apple released macOS 12.3 on Monday alongside iOS 15.4, and it finally adds the long-awaited Universal Control.
Universal Control is now available on select Mac models, which allows you to use a single mouse/trackpad and keyboard across multiple Macs and iPads. Some applications have been available in the past with this functionality, including some that work across Mac and Windows (Logitech Flow is one example), but Apple's closed ecosystem prevented most of those options from working with iPads. Each iPad in a Universal Control setup also needs to be running iPadOS 15.4.
macOS Monterey 12.3 also includes the same new emoji as iOS 15.4, and there are a few under-the-hood changes. The update officially deprecates the kernel extension used by Dropbox, OneDrive, and other cloud sync services. Those applications were broken when macOS 12.3 was in beta, but are rolling out updates that switch to Apple's newer File Provider API. Microsoft updated OneDrive in January to fix the problem, while Dropbox is still working on a fix.
Python 2 has also been removed from macOS with the release of 12.3, though by this point, most Python-powered applications are using Python 3 or a self-hosted Python 2 installation anyway. Check out the changelog above for everything new in this release.
Source: Apple