Differential file sync?

Hi,
I have been looking into the winSCP synchronisation capabilities. Can someone confirm whether it can do differential syncing...?

In other words, if I have a.txt on server A and server B, and I change one character of the file on server A, will an entire copy of the file be uploaded to server B, or just the 1 byte that has changed...?

Thanks!

WinSCP can synchronize whole files only.

Oh well. I think I may have found another solution, should other need one:

Windows now provides WSL - meaning I can use the rsync based lsyncd on a windows box to perform continuous backups.

Cheers!