Can a third client sync a subfolder from two clients that sync the parent folder?

Syncthing looks very interesting and I look forward to trying it out but at the moment I have just one laptop so I decided to ask if the following scenario is possible:

I have the following directories

parent folder
    child folder 1
    child folder 2

I have computer A, A’, and B. A and A’ are mirrored. They sync the parent folder. Computer B only syncs child folder 2 with computer A.

When computer A is turned off, can computer B sync with computer A’?

For some reason I think this scenario wouldn’t work but I’d be happily surprised if it does. I need this functionality because I’ll have two laptops at home (computer A and computer B) and another computer at a remote location that serves as a backup of computer A. This computer is on 24/7. Computer B is a friends’ computer and I only want to share a subset of the folders on my own laptop. But when my laptop is turned off, I still want to allow my friend to sync with the computer on the remote location.

I want to ‘pair’ computer A and A’ just one time and subsequently share sub folders from computer A with computer B but still allow computer B to sync with computer A’ because it has all the same folders as computer A.

I hope the scenario is clear and that it’s possible with Syncthing.

Thanks in advance!

Let everyone just sync the parent folder, and on B ignore some of the folders in the parent to get the subset you are interested in.

Child and parent are different, hence if A’ does not explicitly have a child folder (syncthing folder), B will not be able to get anything from A’, as they won’t even have a folder in common.

Thanks for the reply. I thought about that (that’s one of the reasons why I’m interested in a selective sync option in the GUI) but the problem is that I don’t want to give computer B access to all my files. B is not owned by me, therefore syncing the parent folder with B and ignoring some of the folders would give the user of computer B access to all files. Also, if I add child folder 3 to the parent folder, the owner of computer B would have to add a rule to ignore child folder 3 if I understand your suggestion correctly.

I don’t really get your second sentence. A and A’ will have all folders in common because they mirror the parent folder. B will sync one subfolder from the parent folder and the setup will be done between A and B. If A is offline, will B be able to sync with A’? B hasn’t been explicitly setup to sync with A’ but since A’ contains all the folders of A, and therefore also the subfolder B needs to sync, B should be able to sync with A’ when A is not available. I’d like to know if this scenario is possible.

I hope I explained the scenario clearly.

Selective sync is not going to solve your problem (atleast now how I imagine it). The selective part is for the receiving end, not the sending end, same like it is for dropbox, etc. If you were to enable it on the sending end, then A’ would not be able to access the files either.

Regarding ignores you have inclusions and exclusions so you could have:


which would ignore everything apart from the subdirectory.

My last sentence means that if we have:



  • A shares Folder1 with A’, Folder2 with A’ and B
  • A’ shares Folder1 with A
  • B shares Folder2 with A

that means that if you add A’ on B, B will NOT be able to get content for Folder2 from Folder1 on A’, as they are under two distinctive names, and the file layout within the folder differs.