There are two versions: free and paid but the free has plenty features.

"PureSync by Jumping Bytes is a Windows program to synchronize files and folders, and to do backups e.g. automatically in the background.

Highlights:
Side by side compare view
Automatic synchronization and backups
NAS and FTP support
Easy to use but still many options
It's free*
more
* for personal use only"



Jumping Bytes Software - PureSync - Synchronize and backup files and folders