It is the successor to macOS Mojave and was announced at WWDC 2019 on June 3, 2019 and released to the public on October 7, 2019.

[4][5] In order to increase web compatibility, Safari, Chromium and Firefox have frozen the OS in the user agent running in subsequent releases of macOS at 10.15.7 Catalina.

[6][7][8] The operating system is named after Santa Catalina Island, which is located off the coast of southern California.

[9][10] It is unofficially possible to install macOS Catalina on many older Macintosh computers that are not officially supported by Apple.

[11] Catalyst is a new software-development tool that allows developers to write apps that can run on macOS, iOS and iPadOS.

[19][16] Mac apps, installer packages, and kernel extensions that are signed with a Developer ID must be notarized by Apple to run on macOS Catalina.

[13][23] Sidecar requires a Mac with Intel Skylake CPUs and newer (such as the fourth-generation MacBook Pro), and an iPad that supports Apple Pencil.

[30] iTunes is replaced by separate Music, Podcasts, TV and Books apps, in line with iOS.

Built-in support for Perl, Python 2.7 and Ruby are included in macOS for compatibility with legacy software.

[37] Future versions of macOS will not include scripting language runtimes by default, possibly requiring users to install additional packages.

[40][41] Ars Technica reported that macOS Catalina contained a critical privilege escalation vulnerability, which resulted in a backdoor being installed if users visited a Hong Kong pro-democracy website.

The latest major release of Apple's operating systems (macOS, iOS, and others) receive all security updates.