How to Back Up Your Mac to an External Hard Drive With Time Machine

Say goodbye to lost data with this easy Mac backup process

Your Mac probably has some pretty important files, documents, and photos stored on it, whether they be tax documents, family photos, or that novel you've been noodling around with. In case of damage or theft, that could all be gone in a flash. Thankfully, it's pretty easy to back up your files on a Mac. You can always back up a few files manually, but it's easier than you might think to backup your Mac to an external hard drive with Time Machine.

Time Machine displayed on a Mac.
 TravelCouples / Moment / Getty

When Should You Back Up Your Mac?

Ideally, you should back up your Mac on a regular basis. Manually backing up a few important files here or there is fine for some people, but running Time Machine automatically, and in the background, ensures that you're very unlikely to ever lose any really important data.

If you open the macOS Disk Utility and see this message, you need to start backing up immediately:

  • This drive has a hardware problem that can't be repaired.
  • Back up as much of the data as possible and replace the disk. See an authorized Apple dealer for more information.

How to Back Up Your Mac

There are a bunch of ways to back up your Mac, from manually copying files, to one off and ongoing Time Machine backups, to iCloud and even third party apps. Here are your primary options:

  • Manually back up files: This method requires you to manually copy each file to external storage, so it's only useful if you have a few important files. If you are experiencing disk failure, you may want to use this method to immediately grab your essential files before attempting a full back up.
  • Back up using Time Machine: This method allows you to create a one time backup of all your files or schedule regular updates to happen automatically.
  • Clone your Mac: When you use this method, you end up with an exact copy of your entire hard drive. If your drive fails, or your Mac has booting problems, you can boot from this copy and continue working as normal until you get the problem fixed.
  • Cloud storage like iCloud: Using cloud storage like iCloud or Dropbox, you can automatically upload the contents of specific folders to the cloud. If your local drive fails, you can then download everything that was stored in those folders.

How to Back Up Files Manually on Your Mac

Manually backing up files on a Mac is easy, but it's also time-consuming and not very convenient. It's useful if you just have specific important files to back up, and if those files are unlikely to be changed between the time you back them up and the time of a hypothetical future failure of your hard drive. Files that are changed regularly are poorly suited for this method, as you will need to back up the file again each time you change it.

For anything more complicated than a one-off back up of a few files, skip ahead to the Time Machine instructions in the next section.

  1. Connect an external hard drive or USB flash drive to your Mac.

    A screenshot of a Mac with a USB flash drive connected.
  2. Locate the file or files you want to back up.

    A screenshot of a file folder on macOS.
  3. Select the files you want to back up, and press command+C.

    A screenshot of copying files on macOS.
  4. Open the USB flash drive or external hard drive.

    A screenshot of a USB flash drive on macOS.
  5. Press command+V to paste your copied files.

    A screenshot of backed up files on macOS.
  6. Repeat this process to back up any other essential files.

    If you alter these files in the future, you will need to manually copy the new files to your external storage to back them up again.

How to Back Up Files on macOS Using Time Machine

While it's easy enough to back up a few files manually here and there, macOS comes with a utility called Time Machine that makes the process much easier and can even automate it. If you have a lot of files to back up, or you want to automatically back up files on a set schedule, use Time Machine.

Here's how to perform a one time back up using Time Machine:

  1. Connect an external drive to your Mac.

  2. Click the Apple menu in the upper left corner of the screen, and select System Preferences.

    A screenshot of the apple menu.
  3. Click Time Machine.

    A screenshot of Mac system preferences.
  4. Click Select Backup Disk.

    A screenshot of Time Machine preferences.
  5. Select the disk you want to use, and click Use Disk.

    A screenshot of Time Machine disk selection.

    You can select a local USB drive or storage that's connected via AirPort. If you want to encrypt your data, select that option during this step as well.

  6. If prompted, click Erase to format the disk for use with Time Machine.

    A screenshot of formatting a disk for Time Machine.

    Clicking erase will format the disk, and you will lose any data currently stored there. You will not see this step if your disk is already compatible for use with Time Machine.

  7. Click the check box next to Show Time Machine in menu bar.

  8. Click the Time Machine icon (looks like a clock with a counter-clockwise arrow around it) in the menu bar.

    Highlighted Time Machine icon from Menu Bar.
  9. Click Back Up Now.

  10. Time Machine will automatically back up your hard drive one time. If you want to back up again in the future, you will have to make sure your back up disk is connected and then repeat steps 8 and 9.

How to Automatically Back Up Your Mac With Time Machine

Time Machine can also be configured to back up your files automatically every hour. Each time it runs, it will copy all your files without overwriting the previous copy. When the backup drive fills up, it will automatically delete the oldest files in order to make space for new files. In this way, Time Machine makes sure that you always have the latest version of your files along with at least a few older versions in case you made changes that you want to revert.

Here's how to automatically back up with Time Machine:

  1. Connect an external drive to your Mac.

  2. Click the Apple menu in the upper left corner of the screen, and select System Preferences.

    A screenshot of the apple menu.
  3. Click Time Machine.

    A screenshot of Mac system preferences.
  4. Click Select Backup Disk.

    A screenshot of Time Machine preferences.

    If you've already set a backup disk, skip to step 7.

  5. Select the disk you want to use, and click Use Disk.

    A screenshot of selecting a disk in Time Machine.
  6. If prompted, click Erase to format the disk for use with Time Machine.

    A screenshot of formatting a disk for Time Machine.

    If your disk is already formatted for use with Time Machine, you won't see this step.

  7. Check the Back Up Automatically box.

    A screenshot of Time Machine preferences.
  8. Click Options.

    A screenshot of Time Machine preferences.
  9. Add any folders that you don't want to back up, set the other preferences to your liking, and click Save.

    A screenshot of Time Machine options.
  10. Close the Time Machine preferences window. Time Machine will now automatically back up your files every hour as long as the backup drive is connected.

Backing Up Files With iCloud

Time Machine is great because it allows you to make on-demand backups as well as automatic backups. However, it has a major weakness in that your backed up files are located in the same physical space as your Mac. If you lose your Mac to something like fire or theft, it's likely that your backup drive will also be stolen or damaged.

If you have important files that you absolutely don't want to lose access to, consider backing your files up with iCloud. This is a cloud-based service operated by Apple that you get access to as an Apple user.

By default, Apple users get 5GB of iCloud storage for free, which is enough to store at least some of your most important documents. If you need more space, you can purchase a monthly plan for between 50GB and 2TB of cloud storage.

Create a Bootable Copy Of Your Mac Drive

Every method of backing up that we've discussed so far has involved backing up your own files. If you instead back up your entire drive by cloning it, you can actually create a bootable copy of your drive. If your drive fails in the future, you can connect your backup disk, boot from it, and then either work as normal or work on fixing or replacing your broken drive as time permits.

If that sounds like something you'd like to do, you can use the Disk Utility app to create a clone of your Mac drive. This process isn't that difficult, but it is complicated and time consuming, so some people prefer to use a third party app. To that end, we have a list of the best free Mac backup apps and also a guide to the best Mac backup software.