A backup you can actually restore
The three-copy rule, the difference between sync and versioned backup, and the one five-minute test that tells you whether your setup works.
Nobody plans to have a backup that cannot be restored. It happens because the setup was tested in the wrong direction: the software successfully wrote files somewhere, which feels like proof, but nobody ever read one back.
The fix is one small restore on the day you configure it, and then a decision about which of two quite different problems you are solving.
Sync and backup are different tools
Synchronisation makes two places look the same. If you delete a file, overwrite it, or encrypt it by ransomware, that change travels to the other place within seconds. Versioned backup keeps earlier states, so a mistake from three weeks ago is still recoverable. Most people need both, for different folders.
On our list, Syncthing and FreeFileSync are sync. Duplicati and Restic are versioned backup. Backblaze is an off-site copy that runs without you remembering to attach a drive.
The tools this step calls for, with their real licence and platform details:
| Program | Licence / price | Platforms | Why it is on the list |
|---|---|---|---|
| Syncthing Publisher's site ↗ | Free · Open source | Windows, macOS, Linux, Android | Keeps folders identical across your own devices, peer to peer, with no cloud in the middle and no account. Because deletions propagate, it is synchronisation rather than backup. Pair it with versioning turned on. |
| FreeFileSync Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | Compares two folders and shows you exactly what will be copied, moved or deleted before anything happens, then does it and verifies the result. The clearest free tool for mirroring to an external drive. |
| Duplicati Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | Scheduled encrypted incremental backups to a local drive, a NAS or cloud storage, with a browser interface and retention rules. Good for a home setup. Test a restore before you trust it with anything. |
| Restic Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | A single command line binary that does fast, encrypted, deduplicated snapshots to almost any storage backend. The choice for people who want backups they can script and verify rather than click through. |
| Backblaze Personal Backup Publisher's site ↗ | Paid · From $99/year | Windows, macOS | Unlimited cloud backup of one computer for a flat annual fee, including external drives. The one paid subscription on this page that most households should genuinely consider, because off-site is the part people skip. Free 15-minute restore window for the first 30 days. |
Three copies, two kinds of failure
Keep the working copy, one local copy you control, and one copy away from the machine. The local copy handles a dead drive; the off-site one handles theft, fire and a compromised account. The detail people miss is that the local copy should not be permanently mounted, or anything with access to the machine can reach it too.
The tools this step calls for, with their real licence and platform details:
| Program | Licence / price | Platforms | Why it is on the list |
|---|---|---|---|
| Duplicati Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | Scheduled encrypted incremental backups to a local drive, a NAS or cloud storage, with a browser interface and retention rules. Good for a home setup. Test a restore before you trust it with anything. |
| Cryptomator Publisher's site ↗ | Free + paid tiers | Windows, macOS, Linux, Android, iOS | Encrypts files before they reach Dropbox, OneDrive or Google Drive, so the cloud provider stores scrambled data. The right tool if you must use a mainstream cloud but do not want to trust it. |
| Backblaze Personal Backup Publisher's site ↗ | Paid · From $99/year | Windows, macOS | Unlimited cloud backup of one computer for a flat annual fee, including external drives. The one paid subscription on this page that most households should genuinely consider, because off-site is the part people skip. Free 15-minute restore window for the first 30 days. |
The five-minute test
Pick one small file. Restore it to a different folder, open it, and confirm it is the current version. Then write down, somewhere outside the backup, where the recovery key or passphrase is. If the restore needs a tool you no longer have installed, you have found the problem on a day when nothing is at stake.
Repeat this once a year, and once after any change to the backup software. It is the least exciting maintenance task on this site and the one that decides whether the rest matters.
The tools this step calls for, with their real licence and platform details:
| Program | Licence / price | Platforms | Why it is on the list |
|---|---|---|---|
| Duplicati Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | Scheduled encrypted incremental backups to a local drive, a NAS or cloud storage, with a browser interface and retention rules. Good for a home setup. Test a restore before you trust it with anything. |
| KeePassXC Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | A password database that is just an encrypted file on your own disk. No company, no account, no server to breach. You are responsible for your own backups, which is the trade you are making. |
Mistakes to avoid
- Calling a sync folder a backup and watching a deletion propagate everywhere.
- Keeping the only second copy on a drive that is always plugged in.
- Encrypting the backup and storing the passphrase only inside the backup.
Questions people ask
How often should a backup run?
Often enough that losing a day of work would hurt. For most home machines, daily is comfortable; for active project folders, continuous sync plus nightly versioning.
Is cloud storage a backup?
It is an off-site copy. Whether it is a backup depends on whether versioning is on and whether you have tested retrieving an older version.
Related guides
Or see all guides and category explainers.
How to read this page. How to read this page. Platform, licence and publisher details come from our directory data. Where an independent review, audit or survey is mentioned, it is summarised in our own words with the source named and linked; our /sources page sets out that policy. The recommendation, the trade-offs and every 'skip it if' line are our editorial judgement. We do not run benchmarks, publish measured performance figures or host installers, and every download link goes to the publisher's own site. If a detail is out of date, our About page explains how to tell us.