Syncthing Is Not a Backup Deletions Travel Unless Versioning Is On
The most dangerous sentence in home IT is “my files are synced, so I have a backup.” You do not. This guide explains exactly how sync and backup differ, and how Syncthing's versioning setting closes most — not all — of the gap.
✍️ Technical Anshu🖥️ Windows / Linux⏱️ Read this before trusting sync with real work
🎥 The main Syncthing video shows the sync running — this guide covers the setting that protects it
Syncthing does one job perfectly: it makes every device hold the same files. The trouble is that “same” includes the same mistakes. Delete a folder on your laptop and Syncthing will, within seconds, dutifully delete it from the hub and the phone too. Encrypt your files with ransomware and the encrypted versions sync just as faithfully. A backup is a copy that does not follow the original into disaster. Sync, by definition, follows. Here is how to add the missing protection.
File Versioning — set per folder, best on the hub
FOLDER → EDIT → FILE VERSIONING
( ) No file versioning ....... deletions are final
( ) Trash Can ................ deleted files kept in a
hidden .stversions folder
for a set number of days
(•) Staggered ................ older copies kept across
time — many from today,
fewer from last month,
up to a year by default
( ) Simple ................... keep the last N versions
( ) External ................. hand versions to your
own script or tool
Enable it on the HUB for every shared folder.
Illustrative panel — options shortened from the real versioning settings
1
Three Ways Sync Fails as a Backup
Concrete, common, and all observed in real offices:
The tidy-up. Someone frees space on a laptop by deleting "old" project files. By lunch, they are gone from every machine. There was no other copy, because sync was the copy.
The overwrite. A spreadsheet is saved in a broken state — formulas replaced by values. The broken version is now the version everywhere.
The encryption. Ransomware on one PC encrypts the shared folder. Every device receives the encrypted files as a normal "update". Sync did its job flawlessly, which is precisely the problem.
None of these are Syncthing bugs. They are what "keep everything identical" means, taken seriously.
2
Versioning — the Built-In Safety Net
Syncthing's answer is File Versioning, set per folder. When it is on, a device does not simply destroy the old copy of a changed or deleted file — it moves the old copy aside into a hidden .stversions folder first.
Trash Can keeps deleted and replaced files for a number of days you choose. Simple to understand, easy to restore from by hand.
Staggered is the smart default for the hub: it keeps many recent versions, then thins them out as they age — several from the last hour and day, fewer from last month, spanning up to a year by default. It protects against "I broke this file three weeks ago and only noticed today", which Trash Can's fixed window often misses.
Turn versioning on on the hub, where the big disk lives. It costs disk space roughly proportional to how much your files change — budget for it.
Test a restore once: change a file, let it sync, then find yesterday's copy in .stversions and open it. A safety net you have never used is a hope, not a net.
3
What Versioning Still Cannot Do
Be honest about the remaining holes:
The hub sits on the same network as everything else. Determined ransomware that reaches the hub can destroy the versions too. Versioning stops accidents and buys time; it is not a wall.
If the hub's disk dies, the versions die with the current copies. One device is still one device.
Versioning protects files Syncthing manages. It does nothing for the rest of the PC.
So the full honest setup is: sync for availability, versioning for accidents, and one separate backup for disasters. That third layer can be plain — an external drive that receives a copy weekly and is then unplugged, or a proper backup tool writing somewhere the synced folders cannot reach. Unplugged and offline is a security feature no setting can imitate.
4
A Sensible Layout for a Small Office
Putting it together:
Staff PCs sync their work folders to the hub (Send Only from the PCs, or Send & Receive with the hub only).
The hub holds them Receive Only, with Staggered versioning on, on its largest disk.
A scheduled job copies the hub's folders — including .stversions — to an external drive or a second location, and that copy is rotated or disconnected.
Once a quarter, someone opens a random old file from the backup and confirms it reads fine. Backups that are never test-restored are rumours.
🔴 Remember it in one line: sync protects you from a dead hard disk on one device. Versioning protects you from your own mistakes. Only a separate, disconnected backup protects you from the bad day when everything connected gets hit at once. You need all three layers, and Syncthing honestly gives you the first two.
🎥 Watch the Syncthing Setup in the Video
See the hub, pairing and folder sharing done live — then come back and switch versioning on before you trust it with real files.
Because availability is a real need too: the same file, current, on the machine in front of you, without emailing it to yourself or paying for cloud storage. Sync solves that completely. It just must not be the only protection your files have.
How much extra disk does Staggered versioning use?
It depends on how much your files change. A folder of documents that barely change costs almost nothing; a folder of big files edited daily can grow versions larger than the folder itself. Watch the hub's free space for the first month and adjust — Syncthing also lets you cap versioning by age.
Can I recover a file I deleted a month ago?
If Staggered versioning was on at the hub, very likely yes — look in the folder's hidden .stversions directory on the hub, where versions are stored with timestamps in their names. If versioning was off, the deletion synced everywhere and the file is gone from Syncthing's world; only a separate backup could still have it.
This guide is part of the Syncthing series by Technical Anshu • Watch the main setup video for the full live build 🙏