Alongside the iOS and iPadOS 18.3, the macOS 15.3 also launched, coming in 6 weeks after the macOS Sequoia 15.2 was released and being the third big update for the operating system of the macOS Sequoia that was released in September.
The update can be installed from the Software Update found in System Settings. You can download it for free as long as your Mac can run macOS 15. The macOS 14.7.3 was also rolled out by Apple, as well as the macOS 13.7.3 for Macs that cannot run the macOS 15 and above, providing fixes in security.

macOS Sequoia adds Genmoji for Mac devices that can support Apple Intelligence, making you eligible to make your own custom emojis in your Messages app. Like the iOS and iPadOS 18.3 update, they removed the notification summaries feature for news and entertainment to stop spreading false headlines made by the AI.