A co-worker asked me yesterday if there is a way to use Kdiff3 to synchronize directories similar to BeyondCompare. I briefly attempted this task in the recent past without success. It turns out that it can be done, but I went on to look for dedicated file sync/backup software. Here is a list of what I found:
Whew! This is obviously a common user need. I wonder why it isn't baked into the operating system, or if it is, why it isn't more easily discoverable. I have not evaluated all of these (I've wasted enough time finding the links and making this post ), but I have launched all of them that do not require an install.
I'm currently using SyncBack to back up files between an external drive and my local disks. It is polished, and meets my needs. Feel free to try the others and post your experiences in the comments.
++Alan