Backup and Sync: Why Sync Alone Is Not a Backup (Guide)

What Is the Difference Between Backup and Sync?

Sync vs backup in one view

Question	Sync	Backup
Direction	Two-way between devices	One-way, device to backup
Delete a file	Deleted everywhere	Still in the backup
Ransomware encrypts files	Encrypted copies sync	Clean older versions remain
History	Short trash and limited versions	Versions kept for a set period
Main goal	Same files everywhere	Recovery after loss
Typical tools	OneDrive, Dropbox, Google Drive, Syncthing	Computer backup services, Time Machine, File History

In ten years of backup work, the most painful calls I get start with “but it was synced.” Sync is a great tool. It just does not protect history. This guide shows how backup and sync fit together.

How Does Sync Work?

Sync watches a folder and makes every connected device match it. When you add, edit or delete a file on one device, the sync service repeats that action everywhere else, usually within seconds.

That speed is the whole point. You can start a report on a laptop and finish it on a desktop. However, sync has no idea whether a change was wanted. A mistaken delete looks the same as a planned one.

Most sync services add a trash folder and some file versions as a safety net. These nets have time limits. Google, for example, keeps deleted Drive files in Trash for 30 days, then deletes them forever.

How Does Backup Work?

Backup copies your data in one direction, from your device to a separate store, on a schedule. Each run adds new versions without removing the old ones until the retention period ends.

Because the flow is one-way, a deletion on your laptop does not wipe the backup. You simply pick the date before the problem and restore. For the full process, see our pillar guide on how to back up to the cloud.

Why Is Sync Not a Backup?

Sync is not a backup because it has no independent history. It protects you from a dead laptop, since your files live elsewhere too. It does not protect you from changes that you, an app or malware make.

Deletions travel instantly

Delete a folder to free space on one computer and it disappears on every device. You then depend on the trash, and on noticing in time.

Ransomware rides along

When ransomware encrypts a synced folder, the sync app uploads the encrypted files. Some services can roll a folder back, but limits and time windows apply. A backup gives you a clean, dated restore point instead.

Corruption spreads

A file damaged by a crash or a bad app save syncs like any other change. Without older versions, you sync the broken copy to every device.

One account, one point of failure

If someone takes over your account, or the provider locks it, all synced copies go at once. Microsoft’s Services Agreement itself recommends that users “regularly backup” their content.

When Should You Use Sync, and When Backup?

Use sync for files you work on across devices or share with others. Use backup for everything you cannot afford to lose, including the synced folder itself. Most people need both, running side by side.

• Sync is right for: active projects, shared team folders, documents you open on phone and laptop.
• Backup is right for: photo libraries, archives, tax records, whole computers and external drives.
• Both together: sync for daily access, plus a backup that includes the sync folder.

How to Set Up Backup and Sync Together

The safest setup is simple: keep syncing as you do now, then add a backup that copies the same files to a different company. Follow these steps.

1. Keep your sync app. OneDrive, Dropbox or Google Drive stays in charge of daily access.
2. Make synced files local. Set key folders to “always keep on this device,” so the backup app can read them.
3. Install a backup app. Select your user folders, including the sync folder.
4. Add a local copy. An external drive with Time Machine or File History gives fast restores.
5. Check retention. Choose a backup plan that keeps versions longer than your sync service’s trash.
6. Test a restore. Delete a test file, wait for sync, then restore it from the backup.

Step 6 proves the whole setup works. Our guide on how to check a backup with a test restore explains how to do it on a schedule.

What About Google’s Old Desktop App?

Google’s old desktop app was called Backup and Sync. Google replaced it with Google Drive for desktop, which now handles both Drive syncing and folder uploads. Despite the old name, it still works as storage with a safety net, not as a full backup.

If you use it, read our setup guide for Google Drive for desktop. Then add a separate backup for real version history.

Privacy: Sync vs Backup

Both send your files to a provider’s servers, so encryption and key control matter in each case. Sync services are built for sharing, which adds risk from public links. Backup services rarely share, and many let you set a private key.

Whichever you use, turn on two-factor login. A stolen password on a sync account exposes every device’s files at once.

Common Myths About Sync and Backup

“My sync app has version history, so it is a backup”

Version history helps with single files. However, it usually depends on the file still existing, and it expires after a set time. A backup is independent of your sync folder.

“RAID or a mirrored drive is the same as a backup”

A mirror is sync at the disk level. It copies deletions and ransomware just as quickly. Read more in our guide to a backup of backup with the 3-2-1 rule.

“Sync is enough for a small business”

Shared folders make sync riskier, not safer. One employee’s mistake reaches everyone. Small teams need backup even more than individuals.

Frequently Asked Questions

Is OneDrive a sync service or a backup?

OneDrive is mainly a sync and storage service. Its folder backup feature moves your Desktop, Documents and Pictures into OneDrive, so they sync across devices. Deleted items stay in the recycle bin for a limited time, so pair OneDrive with an independent backup for real protection.

Can sync and backup apps run at the same time?

Yes, and they usually should. The sync app keeps your devices matched, while the backup app quietly copies the same folders elsewhere. Just make sure files are stored locally, not online-only, so the backup app can read them and does not trigger large downloads.

What is one-way sync, and is it a backup?

One-way sync copies changes from a source to a target, without sending changes back. It is closer to a backup, but deletions often still copy across. It becomes a real backup only if the target keeps older versions and deleted files for a set period.

Does Dropbox Rewind make sync safe enough?

Rewind lets eligible Dropbox plans roll a folder or account back to an earlier date, within the plan’s recovery window. It helps a lot after ransomware or mass deletion. However, it still depends on one account, so a separate backup remains wise.

How do I know if my app syncs or backs up?

Delete a test file on your computer and wait a few minutes. If it also disappears from the web view, the app syncs. If you can still restore it from the app’s history weeks later, the app behaves like a backup for that file.