How to Back Up Your Computer Files

In short

A backup is a second copy of your files kept somewhere other than your computer. If the computer is lost, stolen, broken or infected, you can get everything back. This tutorial helps you back up computer files on Windows and Mac using built-in tools, an external drive and cloud storage, and, just as importantly, check that your backup really works by restoring a file.

Before you start

A simple, strong plan is to keep three copies of important files (the original plus two backups), on two different kinds of storage (such as an external drive and the cloud), with one copy away from home, so a fire, flood or burglary can’t take everything. Even one regular backup is far better than none, so start simple and build up.

Decide what matters most. Usually that’s documents, photos, videos and anything you can’t download again. Apps and Windows itself can be reinstalled, so they matter less.

Note that syncing is not quite the same as backing up. Services like OneDrive and iCloud Drive keep folders in step across devices, so deleting a file in one place can delete it everywhere. They do keep deleted files and older versions for a period, which helps, but an extra backup on an external drive gives you a separate copy.

Key terms

• Backup: a separate copy of your files that you can restore from.
• External drive: a hard drive or SSD that plugs into a USB port, used for backups.
• Cloud backup: copies stored online in a service such as OneDrive or iCloud.
• File History / Time Machine: built-in tools on Windows and Mac that back up files to an external drive automatically and keep older versions.
• Restore: copy files back from a backup when you need them.

Lesson 1: back up a Windows PC

Cloud backup with Windows Backup (Windows 11)

1. Select Start, type Windows Backup and open the app.
2. Under Folders, choose the folders to back up, such as Documents, Pictures and Desktop, and select Back up. They’re synced to your OneDrive account.
3. Check how much OneDrive storage you have. The free allowance may not hold large photo libraries; Microsoft’s backup page in Official documentation explains the options.

External drive backup with File History

1. Connect your external drive.
2. Select Start, type Control Panel and open it. Open File History (search for it in Control Panel if you don’t see it).
3. Select your drive and choose Turn on. File History backs up your libraries, desktop and other user folders automatically, keeping older versions.
4. Use Advanced settings to choose how often it saves copies.

Checkpoint: File History shows the date and time of the last backup.

Lesson 2: back up a Mac with Time Machine

1. Connect an external drive to the Mac.
2. Open System Settings > General > Time Machine.
3. Click Add Backup Disk (or the plus button), choose your drive and click Set Up Disk. If asked, allow the drive to be erased and choose whether to encrypt the backup, which protects it with a password you must remember.
4. Leave the drive connected. Time Machine backs up automatically, keeping hourly, daily and weekly copies as space allows.
5. For cloud copies, turn on iCloud Drive and iCloud Photos in System Settings > [your name] > iCloud.

Checkpoint: the Time Machine settings show the drive and a latest backup time.

Lesson 3: make it a habit and test it

1. If you use a laptop, connect the backup drive regularly, for example every week, and let the backup finish before unplugging.
2. Keep the external drive somewhere safe and separate from the computer when it isn’t in use, and consider a second drive kept elsewhere.
3. Test a restore. On Windows, open File History and select Restore personal files, browse to a file and restore it. On a Mac, open a Finder window, then choose Browse Time Machine backups from the Time Machine menu (or use Time Machine from Launchpad), pick a file and click Restore.
4. Include your phone photos: copy them to the computer, as in transferring photos from a phone, so they’re backed up too.

Check that it worked

You know your backup works when you have successfully restored a file from it. Check the last backup date every month, and confirm that new files appear in the backup. If your files are organized in standard folders, as described in our files and folders tutorial, they’ll be included automatically.

If something goes wrong

• The backup drive isn’t recognized: try another USB port and cable, and check the drive in File Explorer or Finder; a new drive may need formatting, which erases it, so check it’s empty first.
• The drive is full: File History and Time Machine remove the oldest versions automatically; if it’s still full, use a larger drive or back up fewer folders.
• Cloud backup stalls: check your internet connection and available cloud storage, and leave the computer on and awake while it catches up.
• You can’t find a file in the backup: search by name in the restore view, and check the dates around when the file last existed.
• Your computer won’t start: your files are still safe on the backup. Windows Recovery options and Apple’s restore process can help get the computer running; read the official guidance before using them.

Ransomware, malware that locks your files, is another reason backups matter; our Windows security basics help prevent it.

FAQ

How often should I back up my computer?

Automatic tools like File History and Time Machine back up continuously when the drive is connected. If you connect the drive by hand, once a week is a good routine, plus before any big change such as a major update.

Is cloud storage enough on its own?

It protects you from a lost or broken computer, but syncing can copy mistakes too. An external drive backup alongside cloud storage gives the best protection.

What size external drive do I need?

Choose a drive with comfortably more space than the files you want to protect, ideally more than your computer’s total storage, so there’s room for older versions.

Can I use the same drive for backups and other files?

You can, but keeping a drive just for backups is simpler and safer. Never keep your only copy of a file on the backup drive.