MacOS Catalina (version 10.15) is the sixteenth major version of MacOS, Apple Inc.'s desktop operating system for Macintosh computers. It is the successor to macOS Mojave. MacOS Catalina was announced at WWDC 2019 on June 3, 2019. Catalina is the first version of macOS to support only 64-bit applications. It will be released as a free update on October 2019.