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Backup Your Computer

Set up and maintain reliable computer backups so you never lose important files

Hard drives fail. Laptops get stolen. Ransomware encrypts everything. The question is not if you will lose data, but when. A good backup means you lose nothing. No backup means you lose everything since the last time you cared enough to copy your files somewhere.

The 3-2-1 rule is the simplest way to think about it: keep 3 copies of your data, on 2 different types of storage, with 1 copy offsite (like the cloud). That sounds like a lot, but once you set it up it runs automatically.

Time Machine (local backup)

Time Machine is built into macOS and backs up your entire Mac to an external drive, automatically, every hour. If anything goes wrong, you can restore individual files or your whole system.

  1. Connect an external drive to your Mac. It should be at least twice the size of your Mac's internal storage
  2. If macOS asks whether you want to use the drive for Time Machine, click Set Up
  3. If the prompt does not appear, open System Settings > General > Time Machine
  4. Click Add Backup Disk and select your external drive
  5. If the drive is not formatted as APFS, macOS will offer to erase and reformat it. This deletes everything on the drive, so make sure it is empty or you have moved those files elsewhere
  6. Once set up, backups start automatically. The first backup takes a while — leave the drive connected until it finishes

To change how often Time Machine backs up or exclude folders you do not need backed up, click Options in the Time Machine settings.

Verifying your backup: Open Time Machine from the menu bar (clock with a circular arrow icon) and browse through past snapshots. If you can see your files at different points in time, your backup is working.

Cloud backup

iCloud Drive: Open System Settings > [your name] > iCloud > iCloud Drive and turn it on. Enable Desktop & Documents Folders to sync those to iCloud automatically. This counts against your iCloud storage (5 GB free, plans up to 12 TB).

Google Drive: Install Google Drive from google.com/drive/download. Open it from the menu bar, sign in, and choose folders to sync or mirror to the cloud.

OneDrive: Install OneDrive from the Mac App Store or onedrive.com. Sign in and choose which folders to sync.

What to back up

Time Machine handles everything automatically. For cloud backups, prioritize:

  • Documents and Desktop folders (most of your work lives here)
  • Photos library (if not already syncing to iCloud Photos or Google Photos)
  • Any project folders outside your home directory
  • App data that lives in non-standard locations (check the app's export or backup feature)

Things you can skip: applications (you can redownload them), system caches, and anything in your Downloads folder that you do not need long-term.

How often to back up

Time Machine runs every hour when your backup drive is connected. For cloud backups, syncing is continuous. The key is to leave your external drive connected (or connect it at least once a day if you use a laptop). If your backup drive only gets connected once a month, you have a month-sized hole in your safety net.

Frequently Asked Questions

How big should my backup drive be?▾

At least twice the size of the data you want to back up. If your computer has a 500 GB drive that is half full, a 500 GB external drive works, but a 1 TB drive gives you more room for versioned backups and future growth. Time Machine and File History both keep multiple versions of files, which takes extra space.

Is cloud backup enough on its own?▾

Cloud backup is great for protecting against theft, fire, or hardware failure. But it can be slow to restore large amounts of data, and if your account gets compromised, your cloud files could be affected too. A local backup on an external drive gives you fast restores. Using both (cloud plus local) follows the 3-2-1 rule and gives you the best protection.

What happens if my backup drive fails?▾

You lose the backup, not your original files. Replace the drive and start a new backup. This is exactly why the 3-2-1 rule recommends multiple copies on different storage. If you only have one backup and it fails, you are back to having zero protection.

Will backing up slow down my computer?▾

The first backup takes time because it copies everything. After that, backups are incremental (only new and changed files), which is fast and runs quietly in the background. You should not notice any slowdown during normal use.

How do I restore files from a backup?▾

On Mac, open Time Machine from the menu bar and browse to the date you want, then click Restore on the file you need. On Windows, open File History and click Restore personal files to browse versions. For cloud backups, sign in to the service's website and download what you need. Each method lets you restore individual files or everything at once.