Apple has used an odd-even cadence for its operating system upgrades' requirements, alternately retaining the prior year's models on the newest version's support list in odd-numbered years with odd-numbered editions, as in 2019's Catalina, macOS 10.15, and dropping models from the list during even-numbered years with even-numbered editions.īig Sur would have been 10.16 if Apple had hewed to tradition, but it's still an even-numbered upgrade because of its year.
