Siri is integrated into the system. Users can access it via the Dock, the menu bar or a keyboard shortcut and results are shown with an interface in the upper-right corner. Siri can send messages, search the web, find files and adjust settings. Results are interactive and can be dropped into other applications or pinned to Notification Center. For instance, pictures from search results can be dragged into a document.
The Photos application now has improved face recognition. It also features 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.
Apple Pay allows vendors to embed an Apple Pay button in their online stores. In Safari, users can click the Apple Pay button to checkout, then securely complete purchases 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.
iCloud Drive has been more tightly integrated into the OS. Users can access all files from iPhone, iPad, Mac, or Windows PC and on iCloud.com.
Optimized Storage can free up storage space. When storage space is low, it automatically uploads old files, photos, movies, and email attachments to iCloud and makes them available on demand. Files that are recently created and recent photos stay on the Mac to allow quick access. Optimized Storage also allows finding and removing files or apps.
The Messages app adds aesthetic effects to messages, such as three times bigger emoji 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.
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.
Applications that support multiple windows will support multiple tabs within a single window, allowing the user to keep windows organized similarly to Safari.
Picture in Picture
Multitasking has been made more convenient with the introduction of Picture-in-Picture, allowing users to watch and float a video window from Safari or iTunes over the desktop or a full-screen app.
With Auto Unlock, when users approach their Mac while wearing an Apple Watch, they are automatically logged in to their desktop account. Time of flight is used to prevent relay attacks. Auto Unlock requires a Mac that was introduced in 2013 or later, and an Apple Watch with watchOS 3.
The clipboard can be shared across nearby macOS Sierra and iOS 10 devices for cut, copy and paste.
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, but will, unlike ZFS, not detect or protect against silent data corruption. The file system is currently experimental and a release is planned for 2017. Apple plans to document and publish the APFS volume format.