Short version On Windows use the built-in command line function robocopy. Long version For copying files from A to B and only moving new ones the simplest way on a recent Windows system is to use robocopy (robust file copy - I thought it was a joke at first) which replaces the ancient xcopy. I use it to back up my PC while I dither about buying some “proper” software or figuring out Windows backup. It can copy across a network and cope with interruptions hence the name “robust”. I wrote a batch file that copies new files, removes deleted files, logs what it has done and shows the log, which I then read as a double check against copy errors. It will work its way through an entire directory tree so input is minimal. The reason for the batch file is that there are several directories I back up and there are a lot of easily mistyped command line switches. It is simpler and more reliable to put the commands in a file. To back up I just plug a usb drive in the PC, check it has been assigned the expected drive letter (my Batch file writes to Drive D and run the batch file. This maintains for me a copy of several key folders that is up-to-date on additions and deletions. The same can be done on Unix and Mac systems using the cp command. Note it isn’t a backup in the sense that you can go back in time and recover something that was deleted or has become corrupted or edited. For that you need custom software. I understand Windows 10 has got reasonably competent backup functionality. If running a Win 10 system I’d look at this if a backup rather than a copy is wanted. Historically Windows backup has had backwards compatibility issues so changing Windows version loses old backup archives but I suspect the risk is less now.