Starting February 15, 2024, Steam will no longer provide support for macOS versions 10.13 (High Sierra) and 10.14 (Mojave). The latter is the final version that supports 32-bit games, so such beloved titles as Civilization IV, Half-Life 2, and Metro 2033 will become unplayable on Macs with those versions of macOS.
The decision to discontinue support for these older macOS versions stems from several factors. First up, macOS Mojave is the final version that supports 32-bit games. Apple's move to stop supporting 32-bit applications in macOS 10.15 has rendered many older games incompatible with newer macOS versions. This change will also be reflected in the Steam store, which will no longer list games with only 32-bit macOS binaries as compatible with Mac at the end of 2023.
Valve says that over 98% of Mac Steam users have migrated to newer macOS versions, so very few people will likely be impacted. Meanwhile, users of the older versions are urged to upgrade for continued access to Steam features and security updates. Furthermore, while Steam and its games may continue to function on these older versions for a time, their performance and compatibility cannot be guaranteed beyond the February 2024 deadline.
