Guide
How to back up your computer properly, on Windows and Mac
Most of the data recovery we do would not have been needed with a working backup. Setting one up takes less than an hour, costs little, and turns a dead drive, a stolen laptop or ransomware from a disaster into an inconvenience. Here is a setup that is simple enough to keep running.
The 3-2-1 rule
You do not need to remember much about backups beyond this. It is the standard that protects you against nearly every way of losing data.
- 3 copies of your data — the original on your computer plus two backups
- 2 different places — for example an external drive and a cloud service — so one failure cannot take both
- 1 copy away from home — cloud storage counts; it protects you against theft, fire and flood
Sync is not the same as backup
OneDrive, iCloud Drive, Google Drive and Dropbox keep files the same everywhere — which means if a file is deleted, overwritten or encrypted by ransomware on your computer, that change syncs to the cloud too. They do keep deleted files and older versions for a limited time, which helps, but they are not a substitute for a separate backup you control. Use sync for convenience and as your off-site copy, and keep an independent backup as well.
Set it up — Windows and Mac
Both systems include a decent backup tool. Plug in an external drive larger than the data you are protecting, and set up the built-in tool so it runs automatically.
On Windows
- File History (external drive) — Control Panel > File History — turn it on with an external drive connected; it keeps hourly versions of your documents, pictures and desktop
- Windows Backup (cloud) — the Windows Backup app on Windows 11 backs up folders, settings and app lists to OneDrive
- Check the folders — make sure anything you keep outside Documents, Pictures and Desktop is included
- BitLocker key — if the drive is encrypted, save the recovery key — it is in your Microsoft account; without it the data may be unreachable
On a Mac
- Time Machine (external drive) — System Settings > General > Time Machine — add a backup disk and it backs up hourly, automatically
- Encrypt the backup — tick "Encrypt backup" when you add the disk, so a lost drive does not expose your files
- iCloud for the off-site copy — iCloud Drive and iCloud Photos give you the away-from-home copy; with "Optimise Mac Storage" on, some originals live only in iCloud
- Leave it plugged in — Time Machine only works when the drive is connected — plug it in at least weekly on a laptop
Test it — the step everyone skips
A backup you have never restored from is a hope, not a backup. Every few months, check it is actually working.
- Check the date — File History and Time Machine both show when the last backup finished — it should be recent
- Restore one file — pick a document and restore an older version to a different folder, then open it
- Check the cloud — sign in on the web and confirm your important folders are there
For small businesses
The same rule applies, with a couple of extras: back up shared and server data as well as each computer, keep at least one copy disconnected or immutable so ransomware cannot reach it, and remember that Microsoft 365 and Google Workspace protect their service, not your data from deletion — a separate backup of email and files is worth having.
See also: Data recovery: what to do first · Setting up a new computer
Worked through these and still stuck? Read us the symptoms and we will tell you what is likely wrong — free, any hour.
Call 0478 953 755Common questions
How often should I back up my computer?
Automatically and continuously, if you can — File History and Time Machine both back up every hour while the drive is connected. If you plug a drive in by hand, weekly is the minimum, and always before an update, a repair or a trip.
Is OneDrive or iCloud enough as a backup?
Not on their own. They sync changes, so a deletion or ransomware on your computer can carry over to the cloud. They are a good off-site copy alongside an external-drive backup, but not a replacement for one.
What size external drive do I need for a backup?
At least as large as the data you are backing up, and ideally two to three times larger so the backup can keep older versions. Check how much space is used on your computer and size up from there.
Should I keep the backup drive plugged in all the time?
On a desktop, leaving it connected keeps backups automatic. The trade-off is that ransomware can reach a connected drive, so for important or business data keep a second copy that is disconnected or in the cloud with version history.
Still not sure?
Describe what the machine is doing and we will tell you what is likely wrong and whether it is worth fixing — before you spend anything. Diagnosis over the phone is free, 24 hours a day.
Call 0478 953 755