Back up the files you're actively working on every day, or continuously with an automatic cloud backup, and the rest of the computer at least once a week. The simplest test: your backup should run more often than the amount of work you could stand to lose. Keep one copy away from your home, and test a restore every month or two.
If redoing a day's work would ruin your week, a weekly backup isn't enough. If the computer is mostly for browsing and everything important already lives in cloud services, you need much less.
Backup frequency by type of file#
| What it is |
How often |
Examples |
| Files you're working on now |
Continuously or daily |
Work documents, school projects, financial spreadsheets |
| Photos and videos you can't replace |
Daily, or as soon as you import them |
Family photos, phone imports, recordings |
| Ordinary personal files |
Weekly |
Downloads you want to keep, older documents |
| Archives that rarely change |
Monthly, or right after you add to them |
Finished projects, scanned paperwork, old photo libraries |
| A full system copy |
Monthly, and before any major OS upgrade |
Apps, settings, the whole drive |
Tighten everything before a big deadline, before travel (laptops get lost and stolen on trips), and before installing a major operating-system upgrade.
Is cloud sync the same as a backup?#
No, and this is the mistake people discover the hard way. iCloud Drive, OneDrive, Dropbox, and Google Drive sync your files across devices. If you delete a file, the deletion syncs. If ransomware encrypts your files, the encrypted versions sync. Most of these services keep version history or a recently-deleted folder for a while, but how long depends on the service and plan.
Sync is still useful. It protects you if the laptop is stolen or dies. It just shouldn't be your only copy.
A real backup is a separate copy that keeps older versions, so you can go back to how a file looked last Tuesday. CISA's #StopRansomware guide explains why this matters: many ransomware variants look for and delete or encrypt any backups they can reach, which is why it recommends keeping offline, encrypted backups and testing them regularly.
The 3-2-1 backup rule#
CISA's data backup options paper recommends the 3-2-1 rule:
- 3 copies of every important file: the original plus two backups.
- 2 different types of storage, so one failure doesn't take out both.
- 1 copy kept off-site, outside your home.
For a household, that usually looks like this: files on your computer, an automatic backup to an external drive at home, and an automatic cloud backup service. The external drive gets you back up and running fast. The cloud copy covers fire, flood, theft, and the drive dying at the same time as the laptop.
An alternative to cloud backup is two external drives, swapped every week or month, with one always kept at work or a relative's house. It's cheaper for large photo or video libraries, but only works if you actually do the swap.
How to set up automatic backups#
On a Mac#
- Plug in an external drive at least twice the size of the data you're backing up.
- Open System Settings, then General, then Time Machine, and add the drive as a backup disk.
- Leave it plugged in regularly or connect it at least weekly. Apple says Time Machine keeps hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for all previous months, deleting the oldest when the disk fills.
On Windows#
- Open the Windows Backup app. Microsoft's guide to Windows Backup explains that it can back up your Desktop, Documents, Pictures, Videos, and Music folders to OneDrive, plus apps and settings.
- Note that the free OneDrive allowance is 5 GB, which fills quickly with photos. You may need a paid plan.
- Because this is sync-based, add a second layer: a cloud backup service, or a backup tool that copies to an external drive with version history.
Whichever system you use, don't leave the only backup drive permanently plugged in if you can avoid it. A power surge, theft, or ransomware can hit the computer and the drive together.
Encrypt any backup that contains personal or financial records, and store the encryption password somewhere you can reach without the computer, like your password manager plus a printed copy at home. An encrypted backup you can't unlock is the same as no backup.
What to back up and what you can skip#
Back up everything you made or can't easily get again: documents, photos, videos, music you recorded, project files, email archives stored locally, tax and financial records (see our tax document guide for how long to keep those), and password manager recovery codes.
You can usually skip installed apps, caches, and the Downloads folder, since you can reinstall or redownload them. Before excluding an app folder, check for license keys, plugin presets, game saves, and local databases that won't come back with a reinstall.
Your phone belongs in the plan too. If original photos only live on your phone and its cloud account, copy them into your computer backup. The phone storage cleanup guide explains how to confirm a backup worked before you delete anything from the phone.
How to test your backup#
A green checkmark only proves the software ran. It doesn't prove you can get the files back. Every month or two:
- Restore three files to a temporary folder: something from this week, a photo from a year ago, and something buried deep in a subfolder.
- Open each one. Make sure the photo isn't a blank thumbnail and the document opens.
- Check the date of the last successful backup on both the drive and the cloud service.
- Check free space on the backup drive and your cloud storage quota.
Also test right after you get a new computer, switch backup software, or change cloud plans. That's when folders quietly fall out of the backup.
Signs your backup has stopped working#
- The last backup date is more than a few days old.
- The cloud backup app shows "paused," a payment problem, or a storage-full warning.
- The external drive makes clicking noises or takes much longer to mount than it used to.
- You can't remember the last time you saw the drive.
Fix the first two right away. For the third, buy a replacement drive and copy the backup over before the old one fails completely.
Make it a routine you don't have to think about#
Automatic backups handle the daily work. What they don't do is check themselves. A monthly reminder to look at the backup date and restore a test file (ChoreLists.com can repeat it for you) covers that gap in about five minutes.
Pair backups with a regular software update schedule. Updates close the security holes that let malware in. Backups get your files back if something gets through anyway, or the drive dies, or you delete the wrong folder.