Apple has ended 32-bit support with the release of OS Catalina, meaning many older games purchased may not run on the free OS update.

Moreover, Steam users will also want to hold off on the update, as the Steam client itself is a 32-bit application.

MacGamerHQ has compiled a list of affected games on MacOS, with many games like the LEGO games no longer working in the new OS.

With the recent Game Manger update, select games can be played on macOS Catalina (10.15), but downloads must be initiated in the Game Manger. If you have already updated your macOS, see these instructions for which games are compatible and how you can install them. Games provided through 3rd party systems (like Steam) are also under the same limitations and restrictions. Some games on those services will see updates too from their developers (but not all, especially really old games). If you are thinking of upgrading to Catalina: Many games will not run!

As of this writing even Valve’s first-party games like Team Fortress 2 and Portal, some of the first high profile games to come to Mac, have also been affected by the update.

While the update may seem sudden, users of High Sierra and Mojave will probably have encountered warnings that Apple would make the sheer jump to 64-bit only.

No statement has been issued by Valve or Apple regarding the issue as of this writing.