Still, for many users, Catalina blocks apps that they've relied on for years. Apple warned us years ago that this change was coming, and there's no doubt that an all-64-bit OS like Catalina is more efficient than an OS that runs both 32-bit and 64-bit code. The biggest change is that Apple ripped out all the code that, in earlier versions, made it possible to run older 32-bit apps in Apple's 64-bit operating system. Best Malware Removal and Protection SoftwareĪpple's latest version of macOS, 10.15 Catalina, looks a lot like earlier versions of the operating system, but is vastly different under the hood.