How to back up your Mac with Time Machine

Time Machine is the backup tool built into every Mac, and it’s the simplest place to start if you’ve never backed up before. You don’t need to buy any software, just a drive to back up to, and once it’s set up it runs by itself.

What Time Machine backs up and how long it keeps it

Time Machine is the backup app built into every Mac, and it copies your apps, music, photos, email and documents to a separate drive every hour.

It leaves out macOS itself and the apps that came with it, which is why restoring a whole Mac starts with reinstalling macOS. Everything you added yourself goes into the backup unless you exclude it.

Older backups thin out over time: Time Machine keeps hourly backups for the past 24 hours, daily ones for the past month and weekly ones for all earlier months. When the drive fills up, it deletes the oldest to make room, but never the last remaining backup. So you can get back a file as it was this morning, two weeks ago, or last spring if the drive is big enough.

On your Mac’s own APFS disk, Time Machine also keeps hourly local snapshots for up to 24 hours. They let you rescue a file you deleted an hour ago even when the backup drive isn’t plugged in, but they sit on the same disk as your files, so they’re no help if that disk fails. For that you need the drive.

What drive to get

Get an external USB or Thunderbolt drive with at least twice your Mac’s storage capacity: for a Mac with 1 TB of storage, a 2 TB drive or bigger.

That’s Apple’s recommendation, and it goes by the total size of your Mac’s disk, not how full it is. The extra room is what buys you those months of older versions. A smaller drive still works, and your Mac tells you if it needs more space. Your Mac counts drive space the same way the box does, so a 2 TB drive shows up as about 2 TB. On a Windows PC the same drive looks smaller, and the TB to GB converter shows why.

Plan to use the drive only for Time Machine, and copy off anything already on it first. Setup may erase it, and a drive formatted for Windows has to be reformatted, which deletes what’s on it.

Back up over the network to another Mac or a NAS

Time Machine can also back up over your home network to a folder shared by another Mac, or to a NAS (network storage box) that supports Time Machine over SMB.

It’s slower than a drive plugged straight in, so Apple suggests a direct connection if speed matters. To use a second Mac, set up the shared folder on that Mac:

1. Open System Settings > General > Sharing and turn on File Sharing.
2. Click the Info button next to File Sharing, then Options, and check that Share files and folders using SMB is on. Click Done.
3. Under Shared Folders, click + and pick the folder that will hold the backups.
4. Control-click the folder, choose Advanced Options, turn on Share as a Time Machine backup destination, and click OK.

Then, on the Mac you’re backing up, choose that folder under Add Backup Disk in Time Machine settings. Both Macs should run macOS 11 or later.

For a NAS, follow the maker’s instructions for Time Machine over SMB. Apple no longer recommends an old AirPort Time Capsule or AirPort Extreme, because they use AFP, which macOS 27 doesn’t support.

Restore a single file

To get back one file or folder, open Time Machine, go back to a date when the file still existed, select it and click Restore.

1. Open the Finder window where the file used to be. For a file that was on the desktop, you can skip this.
2. Press Command-Space, type Time Machine and press Return. It may take a moment to connect to the backup.
3. Use the arrows, or the timeline on the right edge of the screen, to move back through the backups.
4. Select the file, folder or several items and click Restore.

Restored items go back to their original location. If you only want an older version of a document you still have, many apps also offer File > Revert To > Browse All Versions.

Restore a whole Mac with Migration Assistant

To move everything from a Time Machine backup onto a new or erased Mac, use Migration Assistant.

1. Connect the backup drive and turn it on.
2. Open Migration Assistant. On a new Mac it’s part of setup; otherwise it’s in Applications > Utilities.
3. Choose to transfer from a Mac, Time Machine backup or startup disk, then click Continue.
4. Select your backup drive and click Continue, then select a backup and click Continue. To use an older backup, or if Continue is dimmed, click the arrow next to the backup shown and pick one.
5. Choose the categories to bring over, or open one to pick single items, and click Continue.

The transfer can take hours. If the Mac won’t start up normally, reinstall macOS first, then run Migration Assistant.

Keep a second copy somewhere else

One Time Machine drive sitting next to your Mac won’t survive a fire, a flood or a burglar who takes both, so keep a second copy in another place.

The simplest way is a second backup drive, added in Time Machine settings like the first. Time Machine takes turns between them, and each gets the changes since it was last used, so you can keep one at work or at a relative’s house and swap them now and then.

The cloud covers part of it. iCloud keeps photos, contacts, calendars and notes, and iCloud Drive can hold your Desktop and Documents folders, but not your whole Mac. For that, you’d need an online backup service that copies the entire Mac.