MacOS Sierra

System requirements

macOS Sierra requires at least 2GB of RAM and 8GB of storage space and will run on:

Sierra is the first version of macOS since OS X Mountain Lion, released in 2012, that does not run on all computers that the previous version supported. Developers have created workarounds to install macOS Sierra on some Mac computers that are no longer officially supported.

Siri

The user can access the Siri intelligent assistant via the Dock, the menu bar or a keyboard shortcut and results are shown in a window in the upper-right corner. Siri can send messages, search the web, find files and adjust settings. Results can be dropped into other applications or pinned to Notification Center. For instance, pictures from search results can be dragged into a document.

iCloud Drive and Optimized Storage

iCloud Drive can upload the user's documents and desktop directories and sync them to other devices. The System Information application has a new section that gives the user detailed information about space usage per application or file and provides tools and suggestions for freeing up space. For instance, the user can let the system upload old files to iCloud Drive and remove their local copies, keeping them available on-demand in Finder. It can also remove old files from trash automatically. iTunes can delete watched, purchased films and TV programs from its library.

Auto Unlock and Universal Clipboard

Building upon Continuity, an "umbrella term [for] features that facilitate the communication between [Apple devices]" using Bluetooth and Wi-Fi, Sierra adds two features. With Auto Unlock, the user can unlock their user account by holding a paired Apple Watch close to the device. Time of flight is used to prevent relay attacks. Auto Unlock requires a Mac that was introduced in 2013 or later. With Universal Clipboard, the user can share the clipboard for cut, copy and paste between macOS Sierra and iOS 10 devices, including text and rich content, such as pictures or videos.

Tabs and Picture-in-Picture

Applications that support multiple windows can support multiple tabs within a single window, allowing the user to keep windows organized similarly to Safari. With Picture-in-Picture, videos can be played in a floating window that follows the user across the system.

Apple File System

Apple released a preview of a new file system, called Apple File System (APFS), to overcome the limitations of HFS Plus. It is intended for solid-state drives and flash memory and will adopt several features found in modern file systems, such as snapshots and cloning, as well as native support for features that Apple already provides in HFS Plus through supplementary software, such as file-system encryption and trim. The file system is currently experimental and a release is planned for 2017. Apple plans to document and publish the APFS volume format.

Night Shift

Night Shift is new in macOS 10.12.4 beta; it works the same as in iOS. Night Shift reduces blue light at night for better reading; this can be scheduled in the settings app, along with a toggle in Notification Center.

Photos

Apple says it has improved the face recognition of the Photos application, adding object and scene recognition. It groups similar pictures together using faces, locations and object recognition to create "memories". Memories contain picture slideshows with transitions and music selected by the algorithm, which can be modified to the user's liking. The "People" album organizes photos by the people in them, and Places shows all photos on a world map.

Safari and Apple Pay

Safari provides an "extension point" which enables developers to bundle Safari extensions within their Cocoa applications and communicate with them directly from the applications. Safari conceals the presence of installed "legacy" plug-ins – such as Adobe Flash Player, Java applets, Microsoft Silverlight and QuickTime – from websites and requires the user to enable a specific plug-in on a per-use or per-website basis.

Apple Pay allows vendors to embed an Apple Pay button on their websites. In Safari, users can click the Apple Pay button to check out, then complete a purchase using an iPhone or Apple Watch. Apple Pay requires a Mac that supports Continuity (2012 or later models) and either an iPhone 6 or later with iOS 10, or an Apple Watch with watchOS 3.

Messages

The Messages app adds aesthetic effects to messages, such as three times bigger emojis and tap back with hearts or thumbs-up on a message bubble. The ability to play YouTube videos and preview links in a conversation was introduced. Users can view interactive content added to iMessage in iOS 10. The app also allows you to turn on or off read receipts on a conversation by conversation basis.

iTunes

Apple Music within iTunes has been redesigned, making it simpler to find favorite songs and discover new ones. A new "For You" tab has been added, which suggests new music the user might like (similar to the existing Genius). A refined MiniPlayer with the ability to view lyrics while you listen has also been introduced.

Notes

The Notes app allows the user to share and collaborate on notes. This is done by tapping on a share button at the top of the window.

Other changes

Gatekeeper

macOS Sierra slightly changes the Gatekeeper user interface and adds two new mechanisms. A new default in System Preferences hides the "Anywhere" option which allows the user to disable the mechanism and execute programs from any source without needing to approve each new one individually.

The first new mechanism allows developers to code-sign disk images that can be verified as a unit by the system. This allows developers to guarantee the integrity of external files that are distributed alongside the application bundle on the same disk image. An attacker could infect these external files with malicious code and with them exploit a vulnerability in the application, without having to break the signature of the application bundle itself. By signing the disk image, the developer can prevent tampering and force an attacker to repackage the files onto a new disk image, requiring a valid developer certificate to pass Gatekeeper without a warning.

The second new mechanism is "path randomization", which executes application bundles from a random, hidden path and prevents them from accessing external files relative to their location. To avoid this, the developer has to distribute the application bundle and its external files on a signed disk image or in a signed installer package. The user can avoid this mechanism by moving the application bundle without its external files to a new location.

Directory permissions and sudo

The Unix permissions for writing to the /Volumes directory are now restricted to root and no longer "world-writable". Apple expanded System Integrity Protection to /Library/Application Support/com.apple.TCC, a directory that contains a list of applications that are allowed to "control the computer", and restricts write access to programs which were signed with an Apple "private entitlement". The file-hosting service Dropbox has been criticized for manipulating the directory to add their Dropbox application to the list, rather than asking the user to do it for them explicitly in System Preferences.

The sudo command-line utility with which a user can execute a command as another user, typically as root, is configured with the "tty_tickets" flag by default, restricting the session timeout to the terminal session (such as a window or tab) in which the user authenticated the program.

Removed functionality

Sierra removes support for garbage collection from the Objective-C runtime, a memory-management system that was added in Mac OS X Leopard and declared deprecated in favor of Automatic Reference Counting in OS X Mountain Lion. Applications that have been compiled with garbage collection will no longer run.

Apple removed native support for the VPN protocol PPTP and made recommendations for alternatives that it considers more secure.

In the 10.12.2 update the "time remaining" estimate has been removed after complaints of the battery life of 2016 MacBook Pros.

The Game Center app has been removed. However, the service still exists.

Reception

macOS Sierra has received positive reviews. Users and critics have praised the functionality for macOS including Siri and support for Apple Pay in Safari. However, most of the criticism was due to the Messages application not getting many features from iOS 10 and how unreliable Auto-Unlock was. Macworld gave it 4 and a half stars out of 5, praising its new features and stability. Engadget gave it a rating of 87 out of 100 praising the new features such as Siri integration, Universal Clipboard, and Apple Pay while criticizing the unreliableness of Auto Unlock, that "Siri isn't always smart enough" and some of the Messages features are only available on iOS 10.