If you find an old Mac running Snow Leopard or Lion, upgrading to Mavericks (via a bootable installer or if previously purchased) is still a solid choice—it modernizes the system without the heavy resource demands of later versions like High Sierra or Mojave. Mavericks remains a beloved, efficient workhorse in macOS history.
Mavericks brought several beloved iOS features over to the Mac: os x mavericks
OS X Mavericks (10.9): The Free Update That Focused on Efficiency and Power User Features If you find an old Mac running Snow
OS X Mavericks: The Release That Redefined the Mac Experience It allowed the Menu Bar and Dock to
Mavericks fixed one of the biggest complaints of previous versions. It allowed the Menu Bar and Dock to appear on multiple monitors, and let users run full-screen apps on one screen without blacking out the others. 5. A Visual Transition