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Backing up your Mac with Time Machine

Set up the automatic backup built into macOS, encrypt it, and know how to restore a file or the whole Mac.

macOS Tutorial Beginner Published October 19, 2026 Translated October 27, 2026 8 min read Tested on: macOS 27 Golden Gate. Same menus since macOS 13 Ventura. Version française
External hard drive on a MacBook
Photo: Siyuan Hu on Unsplash

Before you start

  • An external drive with at least twice the capacity of the data on the Mac, or a Time Machine-compatible NAS
  • The Mac's administrator password

In plain words

Time Machine is a photographer who comes by every hour to take a picture of your desk. If you throw away a sheet by mistake or the desk burns down, you find yesterday's or last month's picture and put everything back. It does not keep every picture forever: when the album is full, the oldest ones go.

Time Machine is built into macOS: once set up, it backs up the Mac automatically and keeps the history of your files. You can go back to yesterday's, last week's or last month's version.

What Time Machine keeps How long
One backup per hour 24 hours
One backup per day The past month
One backup per week As long as the disk has room

When the disk is full, the oldest backups are deleted.

1. Choose the disk

  • External USB drive: the simplest solution. Get one two to three times larger than the space used on the Mac.
  • NAS (Synology, QNAP…): handy for backing up without plugging in a cable, as long as the NAS offers a Time Machine-compatible share.

Warning

If the disk is not in the right format, the Mac offers to erase it during setup, and whatever it contains is lost. Use an empty disk, or copy the files you want to keep elsewhere before you start.

2. Set up Time Machine

  1. Plug in the disk.
  2. Open the Apple menu → System Settings → General → Time Machine.
  3. Click Add Backup Disk (or +), select the disk, then Set Up Disk.
  4. Tick Encrypt Backup and choose a password.
  5. Click Done. The first backup starts; it can take several hours.

Encrypt your backup

An unencrypted backup disk, lost or stolen, gives access to all your files. Store the password in your password manager: without it, the backup is unusable.

3. Set the frequency and exclusions

In System Settings → General → Time Machine, click Options:

  • Back up frequency: every hour by default. On a laptop, a daily backup is often enough.
  • Exclude from Backups: add folders that do not need backing up (temporary downloads, virtual machines, game libraries).

4. Restore a file

  1. In the Finder, open the folder that contained the file.
  2. Click the Time Machine icon in the menu bar → Browse Time Machine Backups. If the icon is not there, open the Time Machine app from the Applications folder.
  3. Go back in time with the arrows or the timeline on the right edge.
  4. Select the file, then click Restore.

5. Restore the whole Mac

  • On a new Mac: during initial setup, or later with the Migration Assistant app, choose From a Mac, Time Machine backup or Startup disk.
  • After a failure or a disk replacement: if the Mac no longer starts, first reinstall macOS from recovery mode (hold the power button until the startup options appear). Then, as on a new Mac, use Migration Assistant to bring back accounts, apps and files from the backup.

Check that everything works

In System Settings → General → Time Machine, the date of the latest backup must be recent. Test restoring a file once a quarter.

Tip

Time Machine on a disk at home does not protect you against burglary or fire. For full protection, add a copy away from home, as recommended by the 3-2-1 rule.

Sources

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