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What is Time Machine?

Time Machine is macOS's built-in backup tool that automatically keeps hourly, daily and weekly versions of a Mac's files on an external or network disk.

What is Time Machine?

Time Machine has been part of macOS since Mac OS X Leopard (10.5) in 2007. Once a backup disk is chosen, it runs on its own in the background with no schedule for the user to manage. The first run copies everything that is not excluded. Later runs copy only what changed, yet every backup can be browsed as a complete picture of the Mac at that moment.

Retention schedule

  • Hourly backups for the past 24 hours
  • Daily backups for the past month
  • Weekly backups for everything older

When the disk fills, Time Machine deletes the oldest backups to make room, so the size of the backup disk decides how far back a user can go. A common rule of thumb is a disk at least twice the size of the data being backed up.

Backup destinations

  • External drive connected by USB or Thunderbolt. macOS may offer to erase and reformat it; current versions format new Time Machine disks as APFS.
  • Network share on a NAS or another Mac that offers Time Machine support over SMB.
  • Apple Time Capsule, a discontinued Apple router with a built-in disk that still turns up on older networks.

Time Machine can rotate between more than one destination, for example one drive at the desk and another kept off site. Choose to encrypt backups when adding a disk; an unencrypted backup is a readable copy of every file on the Mac.

Setting it up and checking it

On macOS Ventura and later, open System Settings > General > Time Machine and click Add Backup Disk; older versions had a Time Machine pane in System Preferences. The Options button excludes folders, such as a large cache, from backup. The settings screen shows the dates of the latest and oldest backups, which is the first thing to check when a user says backups are working.

Terminal offers the tmutil command for scripted checks: tmutil latestbackup prints the newest backup, tmutil startbackup starts one now, and tmutil listlocalsnapshots / lists local snapshots on the startup disk.

Local snapshots

On an APFS startup disk, Time Machine also keeps local snapshots on the internal drive, so a laptop away from its backup disk can still recover recent versions. macOS deletes them automatically when space runs low, which is why they count as purgeable space. They are not a backup on their own, because they are lost with the internal drive.

Restoring

  • One file or folder: open the folder in Finder, then open Time Machine from its menu bar icon or the Applications folder. Move back along the timeline, select the item and click Restore.
  • A whole Mac after a drive failure: start up in macOS Recovery and choose to restore from a Time Machine backup.
  • A new Mac, or after reinstalling macOS: run Migration Assistant and choose the Time Machine backup as the source to bring over accounts, apps, settings and files.

Troubleshooting

  • Backup disk not available: the drive is unplugged, asleep or on a hub that drops power, or the NAS is offline. Connect the drive directly and check that it mounts in Finder.
  • Old backups disappear: expected when the disk fills. Use a larger disk if the user needs a longer history.
  • The first backup takes hours: normal, because it copies everything. Later runs are short.
  • Lost encryption password: the backup cannot be read. Store the password in an approved password manager.

Time Machine compared with other options

Time Machine is a versioned backup, not a sync service. iCloud Drive keeps files the same across devices, so a deletion syncs everywhere, while Time Machine can bring back yesterday's copy. The closest Windows tools are File History, which keeps versions of files in user folders, and full system image backups. One Time Machine disk in the same room as the Mac is also not a complete plan: the 3-2-1 rule calls for three copies of data on two kinds of media, with one copy off site.

Time Machine on the CompTIA A+ exam

Time Machine maps to Core 2 (220-1202) objective 1.8, macOS features and utilities, and objective 4.3, workstation backup and recovery. For 1.8, know where to turn it on and how to restore a file or a whole Mac. For 4.3, recognize that it makes a full backup first and incremental backups after that, keeping fewer old versions as they age, much like a backup rotation scheme. If a question asks how a Mac user recovers a deleted or overwritten file, think Time Machine. If it asks how to keep the same files on a Mac and an iPhone, think iCloud Drive.

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Related terms

APFS

APFS (Apple File System) is the file system on Macs, iPhones and iPads. It replaced HFS+ in 2017, adding snapshots, clones and native encryption.

cloud backups

Cloud backups refer to the process of storing and protecting data by uploading it to remote servers or storage infrastructure maintained by a cloud service provider.

differential backup

A differential backup copies everything that changed since the last full backup. A restore needs only the full backup plus the most recent differential.

full backup

A full backup is a comprehensive data backup that captures all of the data and files on a storage device or system, providing a complete copy of the entire data set.

macOS

macOS is the proprietary operating system developed by Apple Inc. for its Macintosh line of personal computers, laptops, and servers.

snapshot

A point-in-time copy of a system, storage volume, database, or virtual machine that captures its complete state and data at a specific moment, allowing for later restoration or cloning without affecting the current system.

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