Starting from February 15 next year, Steam clients will no longer support Apple's macOS 10.13max 10.14 system.

CTOnews.com November 30, Valve announced today that Steam clients no longer support macOS 10.13 (High Sierra) and 10.14 (Mojave) systems as of February 15, 2024.

The translation part of CTOnews.com is as follows:

Starting February 15, 2024, Steam will officially stop supporting macOS 10.13 (High Sierra) and 10.14 (Mojave) operating systems.

After this date, Valve no longer pushes any type of update, including security updates, to existing Steam clients of these operating systems.

Steam customer service will no longer provide users with technical support related to the old operating system, and can no longer guarantee that the existing Steam will continue to run on unsupported operating system versions.

Unfortunately, macOS 10.14 is the last version that supports running 32-bit games on macOS.

Apple chose to abandon support for 32-bit applications in macOS 10.15 (released in 2019), and because many developers have not yet updated their games to 64-bit, some games may not run effectively.

The Steam Store will consider stopping offering 32-bit macOS game installation files by the end of 2023.

More than 98% of Steam customers on Mac are already running macOS 10.15 or higher, which means that running 32-bit games and applications is no longer supported on your current system.