Sync is not backup: the difference, with examples

Sync keeps the same files on several devices. Backup keeps old copies of them. If you delete a folder, sync deletes it everywhere. A backup still has it.

Same machinery, opposite goal. One makes your devices agree. The other lets you go back.

What goes wrong with sync

Take three ordinary accidents.

You drag a folder to the wrong place and drop it in the bin. Sync obeys, on the laptop, the desktop and the phone. You overwrite a finished spreadsheet with a half-edited one. Sync obeys that too. Ransomware encrypts your documents. Sync uploads the encrypted versions faithfully.

None of that is a bug. Sync did what you asked.

What the big services give you back

Each of them keeps a safety net. On the entry plans it's short.

Dropbox's help page gives Basic, Plus and Family accounts 30 days of version history. Professional, Essentials, Business and Standard have 180 days, and Business Plus, Advanced and Enterprise have 365. The same page says you can't view or restore previous versions of files that have been permanently deleted.

Google Drive says files in Trash are deleted forever after 30 days. Emptying the trash deletes them at once.

OneDrive has a Restore feature that undoes changes from the last 30 days: deleted, overwritten, corrupted or malware-infected files. Microsoft's page says it is for Microsoft 365 subscribers. After automatic ransomware detection, it pre-fills a suggested restore date. Microsoft says files permanently deleted from the Recycle Bin can never be recovered.

On those entry plans you get about a month. Notice you were missing a file in month two, and you're probably out of luck.

What a backup does differently

A backup is a separate copy, taken on a schedule, that doesn't change when the original does. Three properties matter.

• It keeps history, where sync keeps only the latest state.
• It lives somewhere your accident can't reach: another disk, or another site.
• Deleting a file on your machine doesn't delete it from the backup.

Backblaze is one example. Its personal plan backs up a Mac or PC and connected external drives, with unlimited storage, at 8.25 USD/mo a month billed yearly, or 9 USD/mo billed monthly (Backblaze, checked November 1, 2026). Its page says "Forever" version retention is available for an added fee. It doesn't state the default retention or the fee, so ask before you rely on it for old files. Details are in the Backblaze review and the Backblaze product entry.

So can sync be part of a backup?

Yes, as one copy. A synced folder on a cloud service plus a laptop is two copies of the same state. It protects you from a dead disk or a stolen bag. It doesn't protect you from your own mistakes after day 30.

The usual rule is three copies, on two kinds of media, one offsite. Sync can be one of the three. It can't be all of them.

For Mac owners, the local copy is Time Machine, and you'll want an offsite one next to it: setting up Time Machine with an offsite copy. If Time Machine isn't enough, read best Time Machine alternatives.