Which macOS version introduced the desktop file organization feature 'Stacks'?

The macOS version that introduced the desktop file organization feature Stacks was macOS Mojave. Released as macOS 10.14 in 2018, Mojave could automatically group files on a cluttered desktop into expandable piles.

Desktop Stacks organize files by attributes such as kind, date last opened, date modified, date created, name, or tags. A user can turn the feature on from Finder’s View menu by choosing Use Stacks. Opening a pile reveals its contents, while clicking elsewhere collapses it again, preserving a cleaner desktop without moving files into permanent folders.

The name can cause confusion because Stacks existed earlier as a Dock feature. Mac OS X Leopard introduced Dock Stacks in 2007, allowing folders placed in the Dock to display their contents in fan, grid, or list views. Mojave’s innovation was specifically Desktop Stacks: automatic grouping of files already sitting on the desktop.