Do 2 devices have to be online at the time in order for syncronisation to occur?

Regardless of how short of time span it may be, 2 devices have to be online at the same time, in order to make sycnronisation to occur.

I initially thought that: 1st device could make changes in a file #1, go online and then offline. Then, after this, 2nd device would go online, possibly make other changes in a file #2, but the changes in the file #1 would get syncronised anyway. The ones in the file #2 would get syncronised when the 1st goes online.

But this isn’t the case, for 2 devices have to get online at the same time, even briefly. Because there’s no central server to keep the changes at.


Yes, that’s correct, the two configured devices need to be active at the same time for them to be able to sync the relevant data.

Without the other side being active, Syncthing simply doesn’t know what changed - if anything. As you pointed out, there’s no central server which takes care of the storage or sync-state. The only (default) centralised servers are being used to get two devices to discover each other and connect to one and the other.

It’s also covered in the FAQ :slight_smile: ;

Therefore Syncthing does not upload your data to the cloud but exchanges your data across your machines as soon as they are online at the same time.


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