How to set up Time Machine backups on a Mac

Setting up Time Machine takes a few minutes. Plug in an external drive, ideally at least twice the size of your Mac's storage, open the Time Machine pane in System Settings (under General), click Add Backup Disk, choose the drive and turn on Encrypt Backup when it asks. From then on your Mac backs itself up every hour while the drive is connected, and you can step back in time to get a deleted or overwritten file back.

That is most of it. The rest of this post covers choosing the drive, what Time Machine keeps and for how long, how to tell whether it is really working, and how to restore a file before you need to do it in a panic.

Choose a backup drive

Time Machine needs somewhere to put the backups that is not your Mac's own disk. The usual choice is an external drive that stays at your desk.

• Size. When you pick a drive that is too small, Time Machine itself suggests one twice the size of the disks being backed up. That leaves room for many versions of your files, not just one copy.
• Type. An external SSD is faster and quieter. A spinning hard drive is slower but gives you more space for the money. Either works.
• Use it only for backups. Time Machine may need to erase the drive to format it the way it wants. Don't set up a drive that holds anything you haven't copied elsewhere.
• Not the same drive. A second partition on your Mac's own disk is not a backup. If the disk fails, both go together, and Time Machine warns you if you try.

You can also back up over the network, to a shared folder on another Mac or to a network storage device that supports Time Machine. This is handy for laptops, but slower, and a little more fiddly to set up. If this is your first backup, start with a drive on a cable.

Set it up step by step

The steps below match recent versions of macOS. Older versions put Time Machine in its own settings pane, but the choices are much the same.

1. Connect the drive. Your Mac may ask straight away whether you want to use it for Time Machine. You can say yes there, or carry on below.
2. Choose Apple menu > System Settings, click General in the sidebar, then click Time Machine.
3. Click Add Backup Disk (if a disk is already set up, use the plus button), select your drive and click Set Up Disk.
4. In the sheet that follows, turn on Encrypt Backup and set a password. Add a hint that would mean something only to you.
5. If you want to cap how much of the drive the backups can use, set a Disk Usage Limit on the same sheet. Most people leave it alone.
6. Click Done. If macOS says the drive needs to be erased, check once more that nothing on it matters, then confirm.

The first backup copies everything and can take hours. Start it in the evening and leave the Mac awake and plugged in. Later backups only copy what changed, so they are usually quick enough that you won't notice them.

Why encryption is worth it

A backup drive holds a full copy of your files, your mail, your photos and your documents. If it is lost or stolen and not encrypted, anyone who plugs it in can read it. With encryption on, they need the password.

The catch is that you need it too. Time Machine is blunt about this: you can't restore your data without the password. Save it wherever you keep your most important passwords, somewhere that would survive your Mac dying.

Decide at setup. In recent versions, turning encryption on or off for an existing backup means erasing the drive and starting again.

What it backs up, and how often

Time Machine backs up the things you would miss: your documents, photos, music, mail, apps, accounts and settings. It skips most caches and other files the Mac can rebuild. In recent versions of macOS it does not keep a copy of macOS itself; if you restore a whole Mac, a fresh copy of macOS goes on first and your things come back on top.

By default it runs every hour and thins the backups out as they age:

When the drive fills up, Time Machine deletes the oldest backups to make room. That makes it a safety net for your current files, not an archive. Something you deleted three years ago may no longer be there.

Under Options in the Time Machine settings you can change the backup frequency (every hour, every day, every week or manually), exclude folders you don't need backed up, and on a laptop choose whether to back up on battery power. Excluding a folder full of large files you can download again, like installers or virtual machines, saves a lot of space.

Time Machine also keeps local snapshots from the past day on the Mac's own disk, which is how you can often get back a recent version of a file even when the drive isn't connected. macOS removes these when it needs the space.

Check that it is working

A backup you never check is a hope, not a backup. Two quick ways to look:

• The Time Machine settings. The Time Machine pane shows your backup disk, the span of dates your backups cover, and when the next one is due. The newest date is the one to check.
• The menu bar. Turn on the Time Machine icon in System Settings under Control Center (in some versions it lives in the menu bar settings). Its menu shows the latest backup and has Back Up Now.

If the last backup is days old, the usual reason is simple: the drive hasn't been plugged in. Laptop owners in particular unplug and forget. Keep the drive on the desk next to the charger so that both go in together.

Once every few months, do a test restore of something unimportant. It takes two minutes and is the only real proof your backups work. If you like a routine, the backup check fits neatly into a weekly Mac care routine.

Restore a file

You deleted a file, or saved over it with the wrong version. Here is how to get it back:

1. In Finder, open the folder where the file was.
2. Click the Time Machine icon in the menu bar and choose Browse Time Machine Backups. If you don't have the icon, open Time Machine from your Applications folder.
3. Use the timeline along the right edge of the screen, or the arrows, to go back to a time when the file was there.
4. Select it and press Space to preview it, so you know it is the right version.
5. Click Restore. The file goes back where it came from, and if a file with the same name is there, macOS asks what to do.

To move everything to a new Mac, use Migration Assistant on the new Mac and choose your Time Machine drive as the source. To restore a Mac after a disk failure, macOS Recovery has an option to restore from a Time Machine backup.

One backup is a good start

Time Machine on a drive at your desk protects you from the common problems: a deleted file, a failed disk, a botched update. It does not protect you from a fire, a flood or a burglary that takes the Mac and the drive together.

If your work matters, add a second copy that lives somewhere else. Time Machine can back up to more than one drive and takes turns between them, so you can keep a second drive at home or at a friend's and swap now and then. An online backup service is the other option. iCloud Drive keeps your files in sync across devices, which is useful, but syncing is not the same as backing up: delete a file on one device and it disappears from the others too.

Backups and a full disk

Notchpals doesn't remind you to back up, but one of its Tech care moments sits right next to the subject. When your startup disk drops under 10 percent free, the Tech care character in your crew, Gumdrop or Juice, peeks out of the notch to suggest a clear out, at most once a week.

GumdropYour disk is almost full. Let's sort the keepers from the stale ones!

That is the moment a recent backup earns its keep. With Time Machine running, you can delete old downloads and projects with much less worry, because you can step back and fetch one if you were wrong. Remember the limit above, though: when the backup drive fills, old versions go too, so anything you want to keep for years should live somewhere on purpose. The post on a startup disk that is almost full covers what to clear first, and if a big update is on its way, whether to install it right away is worth a read too. Back up first either way.