Everyone agrees backups matter, and most people find out whether theirs work on the worst possible day. The good news: a solid setup takes an hour once, then runs itself. This guide explains the 3-2-1 rule, why cloud sync isn’t a backup, and exactly how to set up automatic backups on Windows and macOS.
The rule to follow
3-2-1: three copies of your data, on two different types of storage, with one copy offsite. In practice: the files on your computer, an automatic backup to an external drive or NAS, and a cloud backup.
Sync is not backup
Google Drive, OneDrive, iCloud and Dropbox keep files identical across devices. That’s the problem: delete a file or encrypt it with ransomware, and the change syncs everywhere. They do keep limited version history, which saves you sometimes — but a backup is a separate copy that isn’t automatically overwritten by whatever happens to the original.
Similarly, RAID is not backup. Mirrored drives survive a drive failure, not a deletion, a fire or a theft.
Set up local backups
macOS: Time Machine
- Connect an external drive with at least twice your data size.
- System Settings → General → Time Machine → Add Backup Disk.
- Tick the encryption option and store the password in your password manager.
- Leave it connected, or connect it on a schedule you’ll actually keep.
Windows
- File History backs up personal folders to an external drive with version history.
- Full disk images — from tools such as Veeam Agent for Microsoft Windows (free for personal use) or Macrium Reflect — restore the entire system, not just files.
- Windows Backup syncs some settings and folders to OneDrive; treat that as convenience, not as your only backup.
Add an offsite copy
| Option | How it works | Good for |
|---|---|---|
| Cloud backup service | An agent continuously uploads your files (for example Backblaze, iDrive) | Set and forget offsite protection |
| Cloud storage with versioning | You choose folders to sync | Documents you also want to access anywhere |
| Rotating external drives | Two drives; one lives at another location, swapped periodically | Large libraries, no upload bandwidth |
| NAS replication | Your NAS copies itself to a cloud provider or a second NAS | Households and small teams |
Protect backups from ransomware
- Keep at least one backup disconnected from the computer when not in use.
- Use versioned backups so you can restore a state from before the infection.
- Enable snapshots on a NAS if it supports them.
- Use a separate strong password and two-factor authentication on the backup account.
- Encrypt backups, especially portable drives that leave the house.
Test the restore — this is the step people skip
A backup you’ve never restored from is a hypothesis. Once a quarter:
- Pick a random file from a few months ago and restore it.
- Check that it opens correctly.
- Confirm the backup ran recently — look at the last backup date.
- Check free space on the backup target.
What to back up beyond files
- Phone photos (make sure they’re actually uploading, and export periodically).
- Password manager export, stored securely.
- Two-factor recovery codes.
- Email, if you rely on a single provider.
- Software licenses and important scanned documents.
Hardware to pair with this: an external SSD for working files, a NAS for household backups, and a UPS so a power cut doesn’t interrupt a write.