macOS as of Leopard is “certified UNIX” (Single Unix Specv3). Darwin is the “Unix core” that macOS is built on, but it hasn’t been certified by itself[0]. [0]

macOS as of Leopard is “certified UNIX” (Single Unix Specv3). Darwin is the “Unix core” that macOS is built on, but it hasn’t been certified by itself[0]. [0] https://en.wikipedia.org/wiki/Darwin_(operating_system) https://en.wikipedia.org/wiki/Darwin_(operating_system)