macOS Catalina (10.15): overview, features, history and compatibility

Key features and changes

• 64-bit only: Catalina is the first macOS to run only 64-bit applications, ending support for older 32-bit apps and prompting developers and users to update or replace legacy software.
• App restructuring: iTunes was discontinued; its functions were split into Apple Music, Apple TV, and Apple Podcasts apps on the Mac.
• Project Catalyst: A framework that helps developers port iPad apps to macOS, enabling more cross-platform titles in the Mac App Store.
• Sidecar: A feature that lets a compatible iPad act as a second display or drawing tablet for Mac, improving creative workflows and continuity between devices.
• Security and system changes: Catalina introduced a read-only system volume, tougher Gatekeeper checks, Activation Lock on T2-equipped Macs, and expanded privacy controls for data access.
• Accessibility and other additions: Voice Control and refreshed Photos and Reminders apps were among the user-facing improvements.

History and development

Catalina was revealed in June 2019 as part of Apple’s annual developer conference and shipped to users later the same year. Its development highlighted Apple’s push toward modernizing app ecosystems on the Mac and aligning developer tools across iPadOS and macOS. The change to 64-bit-only software was one of the most consequential technical transitions for the platform in years.

Compatibility and upgrading

The release supported a broad range of Intel-based Macs introduced in the 2010s, generally those from around 2012 onward, but specific model eligibility varied. Users were advised to check application compatibility before upgrading because many legacy 32-bit programs stopped functioning. Organizations and individuals often tested critical software in advance or used virtualization to preserve older toolchains.

Notable facts and impact

Catalina accelerated the Mac ecosystem’s move toward modernized apps and security practices. It expanded the Mac App Store’s offerings through Catalyst ports and changed media management by replacing iTunes with specialized apps. Some users raised concerns about app compatibility and the transition, while developers gained new opportunities to bring mobile-style apps to the desktop.

For official details, release notes, and developer guidance see Apple’s resources: macOS overview, Apple developer site, Mac hardware information, previous macOS versions, and coverage from WWDC.