Syncthing
peer-to-peer folder sync with no cloud, no account and no quota
Open source
There is no native macOS front end: the daemon runs in the background and you configure it through a local web interface, so the menu bar apps people recommend are third-party wrappers. It is sync, not backup — a deletion propagates to every device unless you enable file versioning first. Both devices must be awake at the same time, since there is no server holding a copy in between, and restrictive networks sometimes need port forwarding or a relay, which is slower.
Syncthing is for the specific case where you pay Dropbox to keep one folder identical on a laptop, a desktop and a machine at home, and you never once share a link with anyone. It connects your devices to each other directly, encrypts what passes between them, and keeps no copy anywhere else. No account, no quota, no monthly line on the card.
Setup is not an app install. You run it in the background and configure it in a browser at localhost, pairing machines by long device IDs and then setting rules per folder: send-only, receive-only, ignore patterns, how many old versions to retain. Once paired, it is genuinely unattended for years.
It is not a backup, and that is where people get hurt. Delete a file on one machine and it vanishes from the others, exactly as designed — turn on file versioning before you trust it with anything irreplaceable. Devices also have to be awake simultaneously, so a laptop that slept for a week catches up when it wakes and not before.
If what you actually want is a drive in the cloud you can open from a phone browser in a hotel, keep paying Dropbox. If you want your own computers to agree with each other, this does the whole job. Kastelo sells paid support for it, if free software with no support desk is a dealbreaker.
What it looks like
What it does
- Direct encrypted sync between your own devices
- No account, no central server and no storage bill
- Send-only, receive-only and ignore patterns per folder
- File versioning that keeps old copies of changed and deleted files
- Runs on macOS, Windows, Linux, NAS hardware and Android
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Also bought outright in files
The facts
- Price
- Free
- Licence
- Free and open source
- What you get
- No licence to buy, and the source is public.
- Details
- Free. MPL-2.0 open source, no paid tier, no account and no hosted storage to pay for. Kastelo sells commercial support for it separately, which is optional and unrelated to using the software.
- Free trial
- No
- On Setapp
- No
- Minimum macOS
- not stated
- Developer
- The Syncthing project
- Source
- Repository
- Price checked
- 2026-09-22
Check it yourself - Price band
- Free