Imagine the worst. Losing irreplaceable photos because your Mac's hard drive failed. Accidentally deleting your dissertation. You might think it will never happen to you, but all it takes is a glass of water falling on to your MacBook and you could lose everything.

But at least if you've got a backup, the financial outlay of getting a new Mac will be made less traumatic by the fact that you can recover everything from your old one. Luckily Apple makes backing up your Mac really easy, so there really is no excuse not to do it.

We have lots of general advice about the importance of backing up your Mac in a separate article, but in this article we're going to focus on one method in particular: Time Machine.

This tutorial covers everything you need to know about backing up your Mac using Time Machine, including: how to use Time Machine, what to do if Time Machine is too slow, what Time Machine does and doesn't back up, whether Time Machine backs up when your Mac is asleep, what to do if your back up fails due to not enough space, and how to delete old backups. We'll also cover how to backup multiple Macs using Time Machine.

If you want to know how to restore or recover a file from a Time Machine backup you've made previously, read this: How to restore files on Mac using Time Machine.

What does Time Machine do?

How to use Time Machine to back up your Mac

Time Machine is Apple's software to back up your Mac, and it comes with every Mac. All you need is a separate storage device, or a MacOS Server, to back up to.

Time Machine keeps a copy of everything on your Mac. It makes hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for each month. It also creates local snapshots on your Mac. One daily snapshot is saved every 24 hours, beginning from the time you start or restart your computer. One weekly snapshot is saved every week. These snapshots will only exist if you have set up Time Machine to back up to a separate drive, but they are on your Mac, rather than that drive.

This probably sounds like a lot of backing up but it isn't. Time Machine only backs up the changes you have made since the last backup so each backup should be really quick.

That doesn't mean that the new changes overwrite all the old changes. Time Machine stores multiple versions of every thing you are working on. For example, you can see a document as it was when you were working on it last Wednesday, as well as the version from Thursday.

Essentially, if you were constantly working on a document you would have 24 copies of it from the past 24 hours, one copy of it for each day of the last month, and one copy a week from the months prior.

It is also really easy to locate the older versions of a file - which is handy if you have changed your mind about changes that were made a few days ago. When you look through your Time Machine back up everything is organised in exactly the same way as it was in the past.

So, for example, if you had a file on your Desktop before you accidentally deleted it last Thursday you can go to the Desktop folder as it was last Wednesday to recover the file. This is why Apple calls it Time Machine, because you are essentially going back in time to find the file.

The other benefit is that because Time Machine isn't backing up your whole Mac every time, it shouldn't take a whole lot of space up on your backup drive. But when you do get to that point the older backups will be deleted to make space for new ones.

All this backing up means that if you ever get a new Mac you can use your Time Machine back up to 'recover' your old Mac onto your new Mac. All your settings and all your files and folders will be just as you left them.We'll cover how to recover your Mac using the Time Machine back up, and how to copy your Time Machine backup to a new Mac, below.

What you need for Time Machine

You'll need a reasonably large external storage device. This could be a USB, Firewire or Thunderbolt hard drive or SSD that you plug into your Mac, or a NAS drive which your Mac connects to via a WiFi network. We'd advise getting a unit offering at least 1TB if you can afford it.

You can also use Time Machine to back up to a server on your network as long as it's running macOS Server, available here.

Your Mac needs to be running Mac OS X Leopard or later but we'd recommend updating to the latest version of the Mac Operating System.

We have a collection of the best NAS drives here, the best hard drives here and the best SSDs, to help you find the best option for backing up to.

How to set up Time Machine on your Mac

  1. Connect expernal storage to your Mac.
  2. It will need to be formatted as Mac OS Extended (Journaled) - if it isn't, open Disk Utility and follow this guide.
  3. In Big Sur Apple has made it possible to choose between HFS+ or APFS for the Time Machine back up - note that you will need to be running Big Sur on the Mac that you try to recover an APFS backup onto. Read: Time Machine finally gets support for APFS in macOS Big Sur.
  4. As long as the drive is formatted correctly, you should see an alert on your Mac asking if you want to use the drive with Time Machine. Click Use as Backup Disk.
  5. If you don't see the alert, open Time Machine preferences from System Preferences > Time Machine.
  6. Choose Backup Disk, select the storage device you wish to back up to, and click Use Disk
  7. You can choose to Encrypt your backups. If you do that you will need a password to access your backups

How to get a shortcut to Time Machine

If you don't already have a shortcut to the Time Machine menu it will be easier for you if you set one up. This icon was present in El Capitan but disappeared after Sierra launched in 2016.

If you don't see this icon (it looks like a clock with a curved arrow) you can create a shortcut to the Time Machine preferences in the form of a Time Machine icon in the menu on the right-hand side of the top of your screen.

If you don't see this icon open System Preferences > Time Machine and tick Show Time Machine in menu bar.

You can also add Time Machine to your Dock if it's not already there, but this will be a shortcut to the backups rather than the menu. Open your Applications folder and select the Time Machine icon and drag the icon into your Dock.

How often to backup a Mac

You should backup your Mac regularly. The beauty of Time Machine is that it will back up pretty much constantly, but rather than make a complete back up of your Mac every time, the software only copies the things you are working on, so each back up is small and you will hardly notice it happening.

Most other backup methods involve a daily back up of your whole system. The benefit of Apple's method is that you can load up a version of a document you were working on an hour ago, rather than undoing over and over again until you get back to that version.

The important thing is to remember that while Time Machine backs up regularly, it will only do so if your Mac is connected to the device you are backing up to. This could be an external storage device that needs to be plugged into your Mac, so don't forget to plug it in! Speaking of which, your Mac also needs to be plugged in before it will back up to Time Machine.

Alternatively it could be a network attached storage device (a NAS drive) in which case, your Mac should only need to be connected to the same WiFi network in order to back up.

If your Mac hasn't backed up using Time Machine for a while you will see alerts reminding you to back up. Don't wait until a hundred days have passed since your last Time Machine backup and then spill water over your laptop (we say this from experience).

How to force a Time Machine backup

Time Machine will make hourly backups but you can force it to make a backup at any time, perhaps because you are about to shut down your Mac and you want to make sure that the Time Machine back up is up to date first.

Just click on the Time Machine icon in the menu bar and choose Back Up Now, or open System Preferences > Time Machine and choose Back Up Now.

How long will a Time Machine backup take?

Wondering how long the Time Machine backup will take? This can vary widely.

It's likely that if you've only made a few changes since the last backup this one won't take very long: just a few minutes. But if you haven't backed up for a while, or if this is your first backup, it's probably going to take some time.

How to use Time Machine to back up your Mac

To find out how long a backup will take go to System Preferences > Time Machine or click on the Time Machine icon in the menu bar. You will see a progress bar that indicates how many gigabytes of data is being backed up and how much time is remaining.

Initially you will just see Preparing Backup, then you will see how big update will be while the software calculates the time remaining. If it's just a normal backup it's unlikely to take more than five minutes.

If you feel that the Time Machine backup is taking too long there are ways to speed it up, which we look at below.

How to stop a Time Machine backup

If you don't have time to back up now - perhaps you need to shut down your Mac and rush home - you can stop Time Machine from backing up your Mac.

Next to the progress bar described above you will see an X. Click on this to stop the backup. The system will start the back up again in one hour. To start it again see how to force a Time Machine backup above.

If you want to pause a backup and finish it later, select Skip This Backup from the Time Machine menu.

How to stop Time Machine backing up automatically

If the hourly backups become annoying you can disable them - but don't forget to use Time Machine to backup from time to time, and remember that when you do it will take longer because the system won't be making the incremental hourly backups so there will be more to cover.

  1. To stop automatic backups go to System Preferences > Time Machine
  2. Deselect Back up Automatically. (In Mac OS X El Capitan or earlier choose Turn off Time Machine).
  3. When you next want to back up your Mac click on the greyed-out Time Machine icon in your menu bar and choose Back Up Now.

Time Machine can't complete the backup

There are a few scenarios when Time Machine might fail to back up your Mac and when this happens the Time Machine icon in the menu bar will have an exclamation mark in the middle of it.

It could be because the external drive doesn't have enough space; it might have become corrupted because you unplugged the drive without dismounting it first (this is why it's important to make sure you always eject a drive properly before disconnecting it); or it could be that the drive isn't formatted correctly.

To check if the problem is with the device you are backing up to, you could try the following:

If you back up to a server, hold down the Option/Alt key on your keyboard while clicking the Time Machine icon in the menu bar, then choose Verify Backups. If Time Machine finds an issue with your backup, it will display a message with details. Follow the onscreen instructions.

If you back up to an external drive, check that there isn't a problem with the drive you are backing up to. First open Time Machine preferences and turn Time Machine off by deselecting Back Up Automatically, then open Disk Utility (press cmd+spacebar and search for Disk Utility), select the backup device, and use First Aid to check the external backup drive.

If you find that the drive isn't formatted properly - it needs to be Mac OS Extended (Journaled) with a GUID Partition Table (GPT) or it won't work with Time Machine - use Disk Utility to reformat the disk. If you have to reformat you will lose what's on the drive, so make a copy first or find another drive and use that.

Time Machine failed due to lack of space

If Time Machine is unable to complete the backup because there is insufficient space there are a few things you can do.

You could choose to exclude items from your backup. Follow these steps:

  1. Click the Time Machine icon in your menu and choose Time Machine preferences (or open Time Machine from System Preferences).
  2. Click on Options
  3. Click on + and locate any files and folders you want to leave out of the backup. If you have iTunes Match, for example, you could choose not to back up your music library because it will already be backed up in Apple's iCloud.
  4. Alternatively, you could delete old backups from your storage device, although Time Machine should do this itself as time progresses. Open the storage drive in your Finder and locate the backup files in the Backups.backupdb folder. Find some of the older files and delete (you'll also have to remove them from the trash).

We have a separate article on What to do when Time Machine backup is full here.

How to speed up Time Machine backup

The first time you back up using Time Machine, expect it to take some time. Time Machine copies nearly all of the data on your Mac. At least you can keep using your Mac while Time Machine works in the background to back up your data.

If you recently upgraded macOS that could also cause Time Machine to take longer to complete a backup.

It might also take a while to back up your Mac with Time Machine if your previous backup was interrupted, or if a lot of files have changed, perhaps because the back up device hasn't been plugged in for some time.

In these cases you could exclude some items from the backup so there isn't as much data to back up, as above.

If you are backing up over a network to a server, or to a network attached storage device (NAS), it might be faster if you move your Mac to the same room as your router, or connect the storage device to your Mac, or the Mac to your router via an Ethernet cable. This should speed up your network.

If you're using virtualisation software to run other operating systems on your Mac, there might be large disk images including data related to those the other operating systems on your Mac. You might only have changed a few files on in other OS, but Time Machine could back up the whole disk image. For this reason you might want to tell Time Machine to exclude these files when it backs up.

Another thing that can interfere with your backups is Anti Virus software. You might want to exclude your backup drive from the virus scan.

If things are still slow, make sure your software is up to date, restart your Mac, and, if you are backing up over a network, restart your router.

Back up your Mac while asleep

If your Mac supports Power Nap it can perform Time Machine backups while it's asleep or the lid is shut. It just needs to be plugged into the mains.

  1. You can find Power Nap in System Preferences > Energy Saver.
  2. Choose Enable Power Nap while plugged into a power adaptor if it's not already selected under Power Adapter.

How to back up multiple Macs

If you have more than one Mac you don't need more than one external drive for your backups. You can backup more than one Mac to your Time Machine drive. You'll need a external drive big enough to accommodate all the backups though - it's recommended that you add up the space currently used by all your Macs and multiply that by 1.2 for the absolute minimum you will need.

You could just plug your Time Machine backup drive into another Mac. That Mac will start recording its own backups to a separate folder on that drive.

If you don't fancy plugging and unplugging the drive all the time you can back up over the network - but beware that this might be slower than doing so via a wired connection. You could set up a network attached storage device, or a macOS Server, or you could use Personal File Sharing and connect both Macs via the network.