What Is macOS?

Everything you need to know about macOS updates

Apple's macOS is the operating system for the MacBook, MacBook Pro, iMac, and Mac Pro. This OS manages your files, runs your apps, connects to the internet, and more. The latest macOS version is called Big Sur.

macOS 11.0 Big Sur

Release date: November 12, 2020

A customized Safari start page on MacOS 11.0 Big Sur.

Named for the mountainous region in central California, macOS 10.16 Big Sur is the 17th major release of the Mac operating system. Unveiled at WWDC20, the new design of macOS Big Sur is stunningly beautiful and iOS-like familiar.

Unlike Catalina, which delivered minor improvements over Mojave, macOS Big Sur embodies the biggest changes to the Apple operating system in years. One notable change is that it allows the new M1-chip Macs to run iPad and iPhone apps directly on the Mac.

Here are other changes you'll find:

  • The popular iOS Control Center makes its debut on Macs with Big Sur.
  • The Calendar, Mail, Photos, and Messages apps have long-awaited redesigns.
  • Safari produces a privacy report for any website you visit using its Intelligent Tracking feature and monitors your passwords to prevent a data breach.
  • Maps new features include its answer to Google's Street view, entitled Look Around, and Guides from trusted resources.

The key new features include:

  • Safari is 50 percent faster than Chrome.
  • The Control Center.
  • Customizable widgets in the notifications menu.
  • Supports iOS apps on M-1 chip Macs.
  • Spacial audio support for AirPods Pro.
  • Maps app Look Around capability.
  • Improved group messaging in Messages.

macOS 10.15 Catalina

Released: October 7, 2019

macOS Catalina on a MacBook Pro.
Apple, Inc.

Announced in June 2019 at WWDC, macOS 10.15 Catalina (named for the island off the coast of California) is the 16th major release of the computer operating system. It's the first version of macOS to support 64-bit applications only and became a free update to all Mac users in September of 2019.

It features a new development system called Catalyst, which allows developers to target macOS Catalina and iPadOS with the same app. Voice control continues Apple's quest to let you control your Mac with your voice.

Here are other changes that were made in Catalina:

  • Sidecar lets you use an iPad as a second screen through AirDisplay or AirParrot.
  • iTunes was split into three new apps: Music, Podcasts, and Apple TV.
  • iOS devices that are connected to your Mac are managed with the Finder.
  • Find My Mac and Find My Friends were merged into a new app called Find My.
  • Reminders handle attachments, and Siri is smarter about when to notify you.
  • The widget app Dashboard was removed.

These are the key new features:

  • 64-bit applications only
  • Catalyst apps
  • Sidecar iPad second screen
  • iTunes breakup
  • Find My app

macOS 10.14 Mojave

Released: September 24, 2018

macOS Mojave desktop

macOS 10.14, or Mojave, was initially announced in June of 2018 at WWDC and released on September 24th that same year. Named for California's Mojave Desert, macOS 10.14 brought iOS apps Apple News, Voice Memos, and Home to the Mac desktop. It also included a better dark mode and was the last version of macOS to support 32-bit applications (you'll receive a notification when attempting to use these).

The Finder got a new view for file metadata and a new Gallery View to browse files visually. When you take a screenshot, the image appears briefly in the corner of the screen, similar to iOS. macOS Mojave also added video capability to its screenshot tool.

Mojave includes Group FaceTime, which lets you chat with up to 32 people at once using video or audio from your Mac, iPhone, iPad, or Apple Watch.

Safari, Apple's web browser, added tracking protection and sends less information about your system to websites. It can create strong passwords for new online accounts and store them, and autofill forms with them.

The Mac App Store was rebuilt with a new interface and editorial content, bringing it in line with the iOS App Store. There’s a new Discover tab, along with Create, Work, Play, and Develop tabs for easier app discovery. News, Stocks, Voice Memos, and Home (for HomeKit automation) apps came over from iOS with this release. 

Key new features include:

  • Four iOS apps came to the Mac.
  • Improved dark mode.
  • Gallery view.
  • Group FaceTime.
  • Mac App Store improvements.

macOS 10.13 High Sierra

Released: September 25, 2017

macOS High Sierra in the App Store
Tatsuo Yamashita / CC By 2.0 / Flickr

Named for the High Sierra mountain region in California, macOS 10.13 was the 14th release of macOS. This sequel to the previous OS, Sierra (10.12), offered performance and technical updates rather than focusing on a complete overhaul.

Apple replaced the HFS Plus file system with a new Apple File System, which supported technologies like 64-bit inode numbers and flash memory to speed up common file-related tasks like duplicating, finding, and backing up files.

Here are other notable changes:

  • The low-level graphics API Metal got its second release as Metal 2, adding virtual reality and machine learning features and support for external graphics cards. 
  • Photos got an updated sidebar, new editing tools, and the ability to sync photos with tagged People in them with iOS 11.
  • Mail got a new Spotlight search called Top Hits, along with a 35 percent improvement in storage space.
  • Safari added machine learning to block third-party trackers and the ability to block autoplay videos. Reader mode could be set to on permanently.
  • The Notes app got support for tables, and users could now pin notes to the top of their list.
  • Siri gained a more natural voice along with a machine-learning boost to its artificial intelligence. 

Key new features include:

  • Apple File System
  • Metal 2 graphics
  • New Photos features
  • Better storage in Mail
  • Tables in Notes
  • More expressive, smarter Siri

macOS 10.12 Sierra

Released: September 20, 2016

MacBook with macOS Sierra on it
iphonedigital / CC By 2.0 / Flickr

macOS 10.12 Sierra, named for the Sierra Nevada region in California, was the first Macintosh operating system named macOS. It took over for OS X El Capitan (also named after a well-known Californian geographical feature). First announced in June 2016, macOS Sierra came as a free update to El Capitan in September of that same year.

It brought a host of features that exist in macOS today, including:

  • The first Desktop iteration of Siri.
  • iCloud Drive with optimized storage.
  • Auto-unlock for the Mac.
  • Tabbed interfaces for all supporting apps.
  • Picture-in-picture mode to watch videos while doing other work.
  • The first support for Apple File System.
  • Night Shift, a function that reduces blue light from the screen during nighttime hours.

Apps got new features, including:

  • Improved face recognition and new object and scene recognition for Photos, a feature that powered the new Memories photo groups.
  • Safari got new developer tools that supported extensions connecting with third-party apps.
  • Apple Pay got web-based buttons in Safari that let you complete purchases with your iPhone or Apple Watch.
  • Messages got bigger emojis and tap back features, along with the ability to play YouTube videos and preview web links.
  • The Mac Messages app lets you see iOS 10 additions to iMessage and allow you to toggle read receipts on and off per conversation.
  • iTunes got a new For You tab and a lyric feature for its MiniPlayer.
  • Notes let you share and collaborate on specific Notes.

Key new features include:

  • Siri on the desktop
  • iCloud Drive
  • Picture-in-picture mode
  • Night Shift
  • Apple Pay on the web
  • iMessage integrations

More About macOS

macOS is a continuation of Mac OS X (later called OS X, pronounced oh-ess-ten), originally released in 2001. It is built on Unix and shares many under-the-hood similarities to Unix and Linux, most notably multi-user support, pre-emptive multitasking, and access to the system using Terminal. 

OS X was renamed in 2016 as macOS 10.12 Sierra to match Apple's other operating systems like iOS, watchOS, and tvOS.