Valve Software’s Steam gaming marketplace and app will drop support for macOS 10.13 (High Sierra) and 10.14 (Mojave), according to a support page post. The change will go into effect on February 15, 2024.

What will happen exactly? Valve writes:

After that date, existing Steam Client installations on these operating systems will no longer receive updates of any kind including security updates. Steam Support will be unable to offer users technical support for issues related to the old operating systems, and Steam will be unable to guarantee continued functionality of Steam on the unsupported operating system versions.

macOS 10.14 (dubbed Mojave by Apple) shipped more than five years ago, and time has a way of marching on, so this might not seem that momentous at first glance. But there’s a reason it’s particularly noteworthy as these things go: this change means the end of support for the last versions of macOS that could run 32-bit games.

While most of the Steam game library for Mac is 64-bit, there are many 32-bit Mac games that never got updated. If you bought them and install them through Steam, continued access is not guaranteed, even if you’re still running High Sierra or Mojave.

“The Steam store will stop considering games that offer only 32-bit macOS binaries to be Mac compatible at the end of 2023,” Valve writes. The post also notes that fewer than two percent of current Mac users on Steam are running macOS 10.14 or earlier, so this only affects the small number who are holding on to those older versions that supported 32-bit apps.

To be clear, lack of support for macOS 10.14 doesn’t necessarily mean Steam won’t run at all on machines running that OS. It just means Valve won’t guarantee it’ll work, and won’t lift a finger to help if something breaks in the passage of time. It also means users who continue to use the older software could become vulnerable to security risks, disincentivizing continued use.

It appears Valve didn’t take the initiative on this one; rather, it’s responding to Google’s ending of macOS 10.13 and 10.14 support in Chrome. Several parts of the Steam user experience rely on Chrome.

All told, playing historical games on the Mac is a complicated affair due to waves of deprecation. PowerPC gave way to Intel, Intel Macs moved from 32-bit to 64-bit, and most recently, Apple moved the Mac from Intel to Apple Silicon with the M1 chip and its successors. Each of those changes made natively playing certain games from before more difficult or even impossible, though Rosetta 2 allowed the preservation of a lot more 64-bit Intel Mac games on Apple Silicon than was initially feared.