macOS version history - Wikipedia

• Max OS X 10.3 Panther (2003)
  • Safari the default web browser
  • Finder brushed-metal UI
  • FileVault for home folder added
  • X11 compatibility
• Mac OS X 10.4 Tiger (2005)
  • First to run on Intel (partway through the lifetime)
  • Last version to support Classic environment (on PowerPC)
• Mac OS X 10.5 Leopard (2007)
  • Last to run on PowerPC
  • Introduced Time Machine
• Mac OS X 10.6 Snow Leopard (2009)
  • First to run exclusively on Intel
  • Still had Rosetta to allow running PowerPC applications
  • Finder rewritten in Cocoa
  • Last to support 32-bit Intel Macs
• OS X 10.7 Lion (2011)
  • First to be exclusively referred to as “OS X”
  • Removed Rosetta, so PowerPC applications could no longer be run
• OS X 10.8 Mountain Lion (2012)
  • Last to be named after a cat
• OS X 10.9 Mavericks (2013)
  • First to be named after a location in California
• OS X 10.10 Yosemite (2014)
  • Introduced Continuity and Handoff
• OS X 10.11 El Capitan (2015)
  • Last to be referred to as “OS X”
  • San Francisco adopted as system font
• macOS 10.12 Sierra (2016)
  • First referred to as “macOS”
• macOS 10.13 High Sierra (2017)
  • Switch to APFS
• macOS 10.14 Mojave (2018)
  • Introduced dark mode
  • Last to support 32-bit apps
• macOS 10.15 Catalina (2019)
  • Last in 10.x line
  • First to support only 64-bit apps. This can especially affect Steam games that weren’t updated to 64-bit