Doe not look like syncthing has the concept of "vault" (using sync.com parlance) where files are stored in the cloud only.
What the OP is describing is more like apple's iCloud, where files might be offloaded from a device and stored only in the cloud, and downloaded on demand.
Comments
I think you're looking for this: https://syncthing.net/
Doe not look like syncthing has the concept of "vault" (using sync.com parlance) where files are stored in the cloud only.
What the OP is describing is more like apple's iCloud, where files might be offloaded from a device and stored only in the cloud, and downloaded on demand.