At least for Mac gamers, it's the end of an era. Valve will discontinue support for macOS 10.13 (High Sierra) and 10.14 (Mojave) on February 15, 2024. Because Mojave was the final OS to support 32-bit apps, Steam will no longer support 32-bit games on Mac.

Considering everything, Valve deserves commendation for supporting users on older versions of macOS for such a long time. Apple discontinued support for macOS Mojave in October 2021, and support for High Sierra ended in December 2020.

Valve may have wanted to continue supporting the two older operating systems, but it became impossible. According to Valve, Steam relies on Google Chrome for certain parts of its user interface, and Google has already ended Chrome support for macOS High Sierra and Mojave. Moreover, there is little incentive to continue support because 98% of Steam users are already using newer macOS versions and will continue to function normally.

These macOS versions also do not support 32-bit applications, so the recent change already affects them. With Steam also dropping support, games that only offer 32-bit binaries will no longer be considered "macOS compatible."

This change does not mean that Steam will immediately stop working on older macOS versions. However, Valve will not provide security updates or troubleshooting assistance if any issues arise. Therefore, upgrading is the most logical choice from both a compatibility and security standpoint.

If you have previously purchased 32-bit games, you can still attempt to use them. However, there is no guarantee that they will continue to function properly in the future. If something goes wrong, you may be out of luck. Unfortunately, there is often little motivation to provide updated versions of older games that are no longer selling well. Eventually, these older games will become incompatible and cease to work. This has been a reality in the gaming industry for as long as gaming itself has existed.